EP0062365A1 - Process for the manufacture of components from a titanium-base alloy, the component obtained this way, and its use - Google Patents

Abstract

Process for producing a component from a mechanically unstable β-titanium alloy, which shows 3 different shape memory effects: a one-way effect, an almost hysteresis-free but continuous two-way effect (similar to bimetal) over a wide temperature range of the phase transition and an irreversible isothermal effect. Exploitation of the effects in thermal release elements (electrical switches) as well as in fixed or detachable connecting elements for components.

Description

The invention relates to a method for producing a component from a titanium alloy according to the preamble of claim 1, and a component according to the preamble of claim 11 and the use of a component according to the preamble of claim 18.

It has long been known that certain alloys have a so-called memory effect, i.e. have some kind of shape memory. Among them, two main groups have gained technical importance. The first includes alloys based on Ni / Ti (e.g. Buehler, WJ Cross, WB: 55 Nitinol, unique wire alloy with a memory. Wire J. 2 (1969), p. 41 - 49) or Ni / Ti / Cu, secondly the copper-rich or nickel-rich alloys of the β-brass type based on Cu / Zn / Al, Cu / Al, Cu / Al / Ni with Ni / Al (e.g. US Pat. No. 3,783,037 and US PS 4 019 925). A shape memory effect has also been discovered and described in a superconducting titanium alloy containing 35% niobium (see Baker, C .: The shape memory effect in a titanium 35 wt% niobium alloy. Metal Sci. J. 5 (1971), p. 92 -100).

All of these alloys have in common that they do not belong to a group of the generally available classic materials and usually have to be specially manufactured using more or less complex processes. The latter applies in particular to alloys to be produced by powder metallurgy. In addition, the memory alloys that have been used technically up to now have in common that they are almost invariably relatively brittle. The lack of ductility places narrower limits on both their processability and their use or requires corresponding additional process steps that make the finished product more expensive. The common alloys show for the two-way effect a more or less large hysteresis when passing through a temperature / path loop. This hysteresis - especially when it reaches considerable values - is not desirable for all applications.

Memory alloys based on Ni / Ti have a temperature M _S of martensitic conversion of theoretically at most 80 ° C (practically usually not above 50 ° C), which is too low for many applications, especially in the field of electrical thermal switches. In addition, such alloys are expensive, especially if one also takes into account the expensive manufacture of components.

The copper alloys belonging to the β-brass type such as Cu / Al / Ni have a tensile strength which is too low for many practical applications with a maximum of 600 MPa. In addition, their M _S temperature is heavily dependent on the accuracy of the composition - in particular on the aluminum content - which makes their reproducibility difficult. Because it is the aluminum that, due to its high vapor pressure, causes losses that are difficult to control and thus deviations from the melting of the alloys Setpoint analysis leads.

There is therefore a need to expand the field of applicability of the memory effects through a new selection of alloys not previously considered, as well as suitable material-specific processes and corresponding production of components.

The invention has for its object to provide a manufacturing method for a component made of a titanium alloy and a component and its use, which makes use of the martensitic conversion for the purpose of achieving a memory effect. There is also the task of characterizing the memory effect in its various manifestations in more detail and demonstrating its usability in technology.

According to the invention, this object is achieved by the features of claims 1, ₁₁ and ₁₈ .

The invention is described on the basis of the following exemplary embodiments explained by figures.

• Fig. 1 einen Ausschnitt aus einem schematischen Phasendiagramm einer binären Titanlegierung,
• Fig. 2 den Verlauf der rückgewinnbaren Dehnung in Funktion der aufgebrachten bleibenden Dehnung für eine Titanlegierung,
• Fig. 3 den Verlauf der Formänderung über der Temperatur für den Einweg-Effekt,
• Fig. 4 den Verlauf der Formänderung über der Temperatur für den Zweiweg-Effekt,
• Fig. 5 den Verlauf der Formänderung über der Temperatur für den isothermen Effekt,
• Fig. 6 die Abmessungen eines Probestabes für Zugproben,
• Fig. 7 die Abmessungen eines Probestabes für Torsionsproben,
• Fig. 8 die schematische Schnitt-Darstellung eines elektrischen Schalters mit Schraubenfedern,
• Fig. 9 die schematische perspektivische Darstellung eines elektrischen Schalters mit einem Torsionsstab,
• Fig. 10 den Längsschnitt durch eine Schrumpfverbindung in der Ausgangslage,
• Fig. 11 den Längsschnitt durch eine Schrumpfverbindung im Moment des Aufweitens,
• Fig. 12 den Längsschnitt durch eine Schrumpfverbindung nach dem Zusammenbau,
• Fig. 13 den Längsschnitt durch eine Schrumpfverbindung nach dem Lösen,
• Fig. 14 den Längsschnitt durch eine Keramikdichtung,
• Fig. 15 den Längsschnitt durch einen Hohlkörperabschluss vor dem Zusammenbau,
• Fig. 16 den Längsschnitt durch eine Hohlkörperverbindung mit Trennwand vor dem Zusammenbau,
• Fig. 17 den Längsschnitt durch eine Hohlkörperverbindung mit verschiedenen Durchmessern.

It shows:

• 1 shows a section of a schematic phase diagram of a binary titanium alloy,
• 2 shows the course of the recoverable strain as a function of the applied permanent strain for a titanium alloy,
• 3 shows the course of the change in shape over the temperature for the one-way effect,
• 4 shows the course of the change in shape over temperature for the two-way effect,
• 5 shows the course of the change in shape over the temperature for the isothermal effect,
• 6 the dimensions of a test rod for tensile tests,
• 7 shows the dimensions of a test rod for torsion samples,
• 8 is a schematic sectional view of an electrical switch with coil springs,
• 9 is a schematic perspective view of an electrical switch with a torsion bar,
• 10 shows the longitudinal section through a shrink connection in the starting position,
• 11 shows the longitudinal section through a shrink connection at the moment of expansion,
• 12 shows the longitudinal section through a shrink connection after assembly,
• 13 shows the longitudinal section through a shrink connection after loosening,
• 14 shows the longitudinal section through a ceramic seal,
• 15 shows the longitudinal section through a hollow body closure before assembly,
• 16 shows the longitudinal section through a hollow body connection with a partition before assembly,
• 17 shows the longitudinal section through a hollow body connection with different diameters.

1 shows a section of a schematic, subsumed phase diagram of a binary titanium alloy. It is the titanium page. The ordinate represents the temperature scale and at the same time corresponds to 100% Ti, ie 0% alloying element. The alloy element X is plotted on the abscissa in percent (for example% by weight). The solid curves divide the diagram into the α-, (α + β) - and β-phase area. Two further curves M _S and M _d , drawn in dashed lines, are related to the phase transition (martensite formation) occurring during quenching from the β region and are explained in more detail below. You meet the 0 ° C isotherm (abscissa) in points A and B. If a vertical line is set up in B, it meets the β transformation line in G. The isotherm drawn by 0 intersects the vertical line set up in A at point D. CD limits the area from which the titanium alloy must be quenched in order to obtain the desired structural state (so-called "mechanically unstable β-titanium alloy") required for the memory effects.

FIG. 2 shows a diagram in which the course of the recoverable strain r (%) as a function of the primary permanent strain ε (%) is shown as curve a for a titanium alloy. For comparison, line b for ideal recovery (100%) is drawn as a 45 ° straight line. You find that up to permanent Strains of over 2% both lines practically coincide, that the maximum recoverable stretch is approx. 3% and that a permanent primary deformation of over 6% no longer has a memory effect. The diagram is of course of a fundamental nature and the numerical values are different for different alloys. In the present case, it applies numerically to a titanium alloy with approximately 10% by weight vanadium, 2% by weight iron and 3% by weight aluminum (Ti 10 V2 Fe 3 Al).

3 shows a diagram of the course of the change in shape over the temperature for the one-way effect of a β-titanium alloy (in the present case TilOV2Fe3Al). A _S is the temperature at the start of the transformation of the martensite (low temperature phase) into the high temperature phase. A _F represents the corresponding temperature for the end of this phase transition. In the present case a deformation by tension, with a permanent elongation of 2.39% being applied, the recoverable proportion A EI = 1.94%. The arrows indicate the direction of the deformation / temperature loop. The dashed line denotes the pure thermal shrinkage of the workpiece after cooling to room temperature. The diagram has a fundamental character and applies qualitatively to all mechanically unstable β-titanium alloys.

4 shows the course of the change in shape over temperature for a titanium alloy, which shows the two-way effect. The original permanent deformation due to tension here was ε _o = 3.7%, which was higher than for the induction of the one-way effect. The reversible strain Δε _III ⁼ 0.4%, which runs continuously with the temperature, shows practically no hysteresis. The mechanism is different from that of the known Ni / Ti alloys. The material basically behaves like a bimetallic strip. The course of the curve is slightly curved upwards in the said temperature interval between room temperature and approx. 300 ^° C. (concave towards the temperature axis). The statements made under Fig. 3 apply to the principle.

5 shows the course of the change in shape over temperature for the irreversible isothermal effect of the alloy Til0V2Fe3Al. After primary deformation by tension (permanent elongation ε = 2.39%), the one-way effect was first run through from A to A _F , which resulted in the usual shrinkage of Δε _I = 1.94%. After further heating of the material (in the present case to approx. 400 ° C), the isothermal memory effect takes place in the opposite direction, which is equivalent to an expansion of Δε _II ⁼ 0.9%. The statements made under Fig. 3 also apply here.

Fig. 6 and Fig. 7 each show a test rod for tensile and. Torsion samples in the length and diameter dimensions, which need no further explanation. Accordingly, the torsion tests were carried out on hollow cylindrical test bars.

In Fig. 8, an electrical switch is shown schematically in section, which uses coil springs as components. 1 is a housing in which a support 2 is fastened, which supports the bearing 3 for the contact lever 4. 5 each represent a fixed and 6 each a movable contact. The contact lever 4 is held by the springs 7 and 8 in a previously selectable rest position. This can be the location shown (both contact points open) or another location (one contact point closed). 7 is a coil spring made of a memory alloy. It can be designed both as a compression spring and as a tension spring with or without tension. 8 is a common coil spring, which can again act as a tension or compression spring with or without preload. Depending on the intended version of 7 and 8 and the combination of these springs used, 8 counteracts the memory effect of 7 (return or counter spring) or supports it (auxiliary spring).

9 shows a schematic perspective illustration of an electrical switch using a torsion bar. 9 is a base plate on which a torsion bar 10 made of memory alloy is attached at right angles. The latter in turn carries the switching arm 11 at its end, the mobility (pivoting range) of which is indicated by a double arrow. It has a movable contact 6 at its end, which faces a fixed contact 5 which is fastened in the holder 12.

10 to 13 show the process sequence in the production of a fixed and a releasable connection. 14 each represents a pipe to be connected in longitudinal section. 13 is a sleeve made of a memory alloy, the inside diameter of which, in the initial state, is undersized compared to the outside pipe diameter. 15 shows the sleeve during the expansion process by means of a ball 16. FIG. 17 shows the sleeve after the shrinking process (one-way memory effect) above the pipes 14. This corresponds to the state of a firm pipe connection. Fig. 13 shows the state after loosening (if necessary) the same connection. 18 is the the sleeve is loosened again after the expansion process due to the isothermal memory effect.

14 to 17 show exemplary embodiments of seals, hollow body endings and hollow body connections. 19 represents a disk made of a memory alloy provided with a groove 20. 21 is a hollow body made of ceramic material which engages in the groove 19 in a vacuum-tight manner. The disc 22 provided with a conical backward rotation 23 is made of a memory alloy. The hollow body 24 to be connected, made of metal, plastic or ceramic material, is indicated by dashed lines before assembly. 25 represents a disk made of a memory alloy, which is offset on both sides and each has a cylindrical undercut 23. The ends of the hollow bodies 24 can, as indicated, have different shapes. In the present case, the disc 25 serves both as a connecting element and as a partition. 26 is a stepped hollow body made of memory alloy, which has the back turns 23 and a central opening 27. The hollow bodies 24 to be connected can be of different diameters and of course of different materials.

Among the titanium alloys there are those that show memory effects after a suitable thermal and thermomechanical pretreatment. The range of composition of these alloys is relatively narrow. The first condition is that they contain at least partially the body-centered / 3-phase in the stable initial state at room temperature. Pure α alloys thus fail. The same applies to pure β-alloys at room temperature, since phase transformation no longer takes place in that area (β-phase stable down to room temperature). In practice, the alloys must therefore fall into the heterogeneous (α + β) phase space at room temperature. A further limitation in the composition is that the alloys must belong to the class of mechanically unstable / 3-titanium alloys (in the sense of this invention), which are basically defined as follows:

Alloy, characterized by the property that its body-centered cubic β phase can be at least partially converted into the stress-induced martensitic α "phase by applying a permanent deformation.

In practice, this can be determined by first subjecting the beta titanium alloy to a thin sheet with a maximum thickness of 1 mm, which is then subjected to solution annealing above the β transition temperature and then within a cooling time of at most 10 seconds to go through the difference between solution annealing temperature and 100 ° C in ice water is deterred. After quenching, the material must have a maximum of 10% by volume of thermally induced martensite.

Furthermore, the alloy is characterized in that the β-phase is converted into martensite (α ") during subsequent mechanical deformation. The maximum temperature at which mechanically induced martensite (α") can be determined after this deformation _is defined as _A M _d .

The course of the M _S and M _d line over temperature is shown in the schematic, subsumed phase diagram in FIG. 1. M _S represents the temperature at which martensite begins to form. M _d has already been defined in more detail above. For the alloys in question at room temperature, there is therefore the condition that their composition must fall approximately in the range between A and B (intersection of the M _S and M _d line with the O ^O C isotherms). In order to fully achieve the desired memory effects, it is desirable to generate as much stress-induced martensite as possible in the subsequent primary permanent deformation. This is achieved by first quenching the component from an area above the β conversion line, as indicated by the dash-dotted vertical line with the arrow on the right. At least one should quench from a temperature corresponding to the isothermal CD, since the above condition can no longer be met when quenching lower temperatures. This is indicated by the dash-dotted vertical on the left with an arrow. In the latter case, however, one then loses a small proportion of material indicated by the lever law, which converts into the stable α phase on the transition via the β conversion line and is lost for the memory effect. However, the conditions for the subsequent formation of martensite are still optimal for the remaining portion of the β phase.

genügen, wobei X_i die Konzentration des jeweiligen Elements in Atomprozent bedeutet und die Koeffizienten A_i und B₁ dem jeweiligen Element gemäss nachfolgender Tabelle zugeordnet .sind:

According to the inventive definition of mechanically in In principle, stable β-titanium alloys are suitable for all alloy elements which have a stabilizing effect on the cubic, body-centered β phase. These are V, Al, Fe, Ni, Co, Mn, Cr, Mo, Zr, Nb, Sn, Cu, which can be used both individually and in combination. For these elements, certain concentration limits can be specified which satisfy the above conditions, which can be derived from the thermodynamic equilibria. As a result, it is possible to mathematically express the alloy composition with the help of empirically determined relationships by a quadratic approximation. The condition must be met that the concentration limits of the alloying elements of the titanium alloy of the formula, expressed in atomic percentages

are sufficient, where X _{i means} the concentration of the respective element in atomic percent and the coefficients A _i and B _{1 are} assigned to the respective element according to the following table:

Titanium alloys belonging to the binary type are particularly suitable and, in addition to titanium, also 14 to 20% by weight vanadium or 4 to 6% by weight iron or 6.5 to 9% by weight manganese or 13 to 19% by weight Contain molybdenum.

Further preferred alloys are those of the ternary type and, in addition to titanium, also 13 to 19% by weight vanadium plus 0.2 to 6% by weight aluminum or 4 to 6% by weight iron plus 0.2 to 6% by weight .-% aluminum or 1.5 to 2.3 wt .-% iron plus 10 to 14 wt .-% vanadium.

There is also a group of alloys which belong to the quaternary type and, in addition to titanium, also contain 9 to 11% by weight of vanadium plus 1.6 to 2.2% by weight of iron plus 2 to 4% by weight of aluminum.

The mechanically unstable / 3-titanium alloys defined and characterized above (in the sense of this invention) show three shape memory effects depending on the thermomechanical or mechanical pretreatment and depending on the temperature range. If tension is exerted on such an alloy by tension, pressure, shear or a combination of at least two of these operations in such a way that a primary permanent deformation is generated, the prerequisites for the setting of a memory effect are given. By heating the component to a temperature above A _S following the deformation, the one-way effect is initially established (see FIG. 3). With further heating up to _AF , the effect that exists in a deformation opposite to the original direction of deformation has ended. A _S and A _F give the temperature of the beginning or ending reconversion of the martensite into the high temperature phase. In contrast to conventional memory alloys, mechanically unstable β-titanium alloys An and A _{F are} relatively high (in the area above 100 ° C), which opens up a new area of application. If the component is cooled from a temperature near A _F to room temperature, the deformation achieved by the one-way effect remains. In this way, for example, fixed connections of components can be realized. If the primary permanent deformation is increased to a certain extent, then after subsequent warming, the one-way effect occurs again when crossing the section between A _S and A _F. If something is now heated above A _F , the material is now in the state where it shows a two-way effect (see FIG. 4). When it cools down from a temperature range of approx. 300 to 350 ° C to room temperature, the component undergoes a deformation which runs in the opposite direction to that of the one-way effect, and is therefore aligned with the originally applied permanent deformation. In contrast to the conventional memory alloys of the Ni / Ti and β-brass types, this deformation with temperature takes place continuously and practically without hysteresis: the behavior of the material is therefore more similar to that of a bimetal. In the present case of Til0V2Fe3Al, the curve is not linear but slightly curved, so that it appears concave towards the temperature axis. If a material pretreated in the usual way for the one-way effect is heated significantly above A _F and kept at the temperature reached, a third effect, the isothermal memory effect, can be observed (see FIG. 5). The component deforms in the opposite direction to the one-way effect. In case of The above-mentioned titanium alloy triggered this effect at approx. 400 ° C. It is irreversible and is due to the conversion of the martensitic α "phase into the stable α phase. The structure then essentially consists of the stable phases. Α and β. This effect can be used, for example, to construct a releasable shrink connection.

When producing the component from the titanium alloy, it is necessary to cool the workpiece from the above-mentioned temperature range - preferably above the β conversion line - at a speed that is high enough on the one hand to maintain the mechanically unstable β phase and on the other hand that Suppress formation of any new phase except the athermal ω phase. Another condition is that at most the formation of a maximum of 10% by volume by quenching thermally induced martensite should be permitted. It is therefore a question of dragging the β-structural state down as far as possible down to room temperature. The ideal case is 100% mechanically unstable / 3-phase. The martensite should only form afterwards by applying a deformation, ie stress-induced. As far as the athermal ω phase is concerned, its formation can often not be avoided entirely. Any (ω-excretions are undesirable for the stability of the memory effect. The upper limit of the meaningful permanent deformation for inducing the martensite results from the fact that the plateau of the recoverable elongation is exhausted with larger deformations (see Fig. 2, where this Limit for Til0V2Fe3Al is about 6%.) In the following, the temperature A _{S ',} which has already been described in general terms above, is intended to be procedural in terms of this invention African size can be defined more precisely. A _S is to be understood as the temperature at which 1/100 of the previously applied primary permanent mechanical deformation is reduced. A ₉₀ , which is characteristic of the memory effects, is to be introduced. This is to be understood as the temperature at which the structure of the component still contains a maximum of 10 vol.% Martensite after previous deformation and subsequent heating.

If the one-way effect is to be achieved, the workpiece must be heated to a temperature above A _S after primary deformation. In the case of the isothermal effect, the workpiece must be heated to a temperature at which the stable α phase separates, and it must be kept at this temperature until at least ₁ % by volume of the original phase has entered the α - Have converted phase. If the two-way effect is to be used, the workpiece must be heated to a temperature above A ₉₀ after primary deformation and then cooled to a temperature below A _S. The aforementioned conditions are the minimum conditions in order to achieve the said memory effects at all. The optimal one-way effect is only obtained after heating to a temperature around A _F. For the isothermal effect, in general, heating to at least 50 ⁰ C above the A _F point lying temperature is necessary. The two-way effect can be achieved by heating to a temperature between A _S and A _F , the structure consisting partly of the aC "phase and partly of the β phase.

Embodiment I:

Beta titanium alloys are generally made by double-arc melting with an consumable electrode. The starting material is titanium sponge and corresponding master alloys. The melting process takes place under vacuum or protective gas with a low hydrogen partial pressure. To produce a component, the components are mixed, melted and cast, and the workpiece obtained in this way is thermoformed and subjected to solution annealing in the temperature range at least in part of the stable / 3 phase. The workpiece is then quenched to room temperature and subjected to mechanical deformation and further thermal treatment.

In the present case, semi-finished products in the form of a cylindrical forging piece with a diameter of 254 mm and a weight of 130 kg were assumed. The titanium alloy corresponded to the designation Ti-10V-2Fe-3Al and had the following actual composition:

Samples were made from the material in the delivery state, namely tensile samples according to FIG. 6, and hollow torsion samples according to FIG. 7.

In order to establish a clearly reproducible initial state, the samples were in the area of the β phase 850 ⁰ C solution annealed for 60 minutes and then quenched in moving water to room temperature. In order to exclude oxidation during solution annealing, the heat treatment was either carried out in a vacuum oven or the samples were placed in an airtightly sealed quartz glass ampoule filled with protective gas. The glass ampoule breaks immediately when immersed in the quenching medium (water), thus allowing rapid quenching. Both during heat treatment under vacuum and when using the protective gas-filled ampoule, the samples were additionally wrapped loosely in zirconium foil in order to bind residual oxygen due to its high affinity for zirconium.

In order to obtain the one-way effect, tensile specimens were deformed at room temperature with a strain rate £ = 0.0007 sec ^-1 . Samples that were permanently deformed up to 3% returned to their original length (before the deformation) practically completely after they had been heated to 300 ^° C. in a salt bath and kept at this temperature for 60 seconds. Samples that were deformed by more than 3% also showed a one-way effect, but did not return completely to their original shape. With deformations of more than 7%, no memory effect was measurable (see Fig. 2). With a primary deformation using pressure instead of tension, the same phenomena could be determined with the same results.

The one-way effect measured on a tension rod is shown schematically in FIG. 3. Similar results are obtained with torsion bars or with the reversal of the deformation (pressure load).

Example II:

Tensile and torsion specimens were produced from the same material and according to the same method as given in Example I. A tensile test was stressed at room temperature to produce a permanent set of 3.7%. When heated, the sample initially showed a one-way effect, i.e. shrinkage occurred in the longitudinal axis (qualitatively similar to Fig. 3). After cooling to room temperature, there was an expansion in the longitudinal direction. The sample was then cyclically heated and cooled a few times. The corresponding expansion or contraction between room temperature and approx. 340 ° C was 0.4% (two-way effect).

Example III:

A torsion bar (see FIG. 7) was produced from Til0V2Fe3Al according to Example I. The bar was at room temperature to 1.16 rad (ε corresponding = _5, 8%) twisted. After the load was removed, the spring deflected back to a twist value of 0.774 rad (corresponding to ε = 3.87%). When heating to 320 ^° C., the deformation decreased to 0.61 rad (corresponding to E = 3.05%). Upon subsequent cooling to room temperature, the deformation increased by 0.098 rad (corresponding to ε = 0.49%). A further heating to 300 ⁰ C reduced the deformation again by 0.082 rad (corresponding to ε = = 0.41%). After 5 heating / cooling cycles between room temperature and 320 ° C, there was a deformation difference of 0.078 rad (corresponding to ε = 0.39%). This torsional two-way effect corresponds qualitatively (not exactly numerically) to the phenomenon shown in FIG. 4.

Example IV:

According to Example I tensile specimens were machined from Til0V2Fe3Al and deformed as described therein and heated to 300 c ^0th As expected, the one-way effect occurred in the form of a corresponding shrinkage in the longitudinal direction of the rod. The samples were then heated to a temperature of 400 to 450 ° C. and held at this temperature for 100 minutes. The test bars extended in the longitudinal direction from the values which were in the order of magnitude of 1 to 2%, depending on the primary deformation applied. This irreversible isothermal effect, which runs counter to the one-way effect, is shown qualitatively in FIG. 5. Elongation values from to rel. 50% (based on the primary permanent set applied) can be achieved.

Embodiment V:

See Fig. 8.

A wire was produced from the material according to Example I and after the pretreatment specified there, and a coil spring 7 was wound therefrom. This spring was then subjected to a treatment according to Example II or III in order to bring about the two-way effect in such a way that the spring 7, which is in the idle state at room temperature under a slight compressive preload, contracts gradually as the temperature rises. The spring 7 made of memory alloy was assembled in an electrical switch according to FIG. 8 together with an ordinary compression spring 8. The current is passed through the spring 8. In the normal state, it causes no heating, so that the latter is practically at room temperature and is in equilibrium with the counter spring 8. In case of overcurrent the spring 7 and this relieves the counter spring 8, so that the upper contacts 5/6 close and, for example, thereby trigger a main switch to interrupt the circuit. Of course, all the reverse combinations of 7 and 8 can also be carried out, as described under FIG. 8.

Embodiment VI:

See Fig. 9.

A torsion bar according to FIG. 7 was produced from the material according to Example I and after the pretreatment specified there. The latter was treated further in accordance with Example II or III in order to produce the two-way effect. The prepared torsion bar 10 was now provided with a switching arm 11 and mounted on the base plate 9. All other components of the electrical switch result from the description of FIG. 9. The torsion bar 10 can be directly flowed through by the current (direct heating) or tightly enclosed by an insulated heating coil (indirect heating). The trigger mechanism is basically the same as that given in Example I. The counter spring is omitted here. This construction is characterized by great simplicity. The trigger temperature can be set within wide limits by suitable selection of the switch geometry (length of the switching arm and swivel range etc.).

Working example VII:

See Figs. 10 through 13.

A hollow cylindrical sleeve 13 of 20.25 mm inside and 26.25 mm outside diameter with 30 mm axial length was produced from Til0V2Fe3Al. It served to two pipes 14 (metal, plastic, ceramic material) of 20.6 mm To connect outside diameter. The sleeve 13 was pretreated according to Example I (solution annealing, quenching). Thereupon it was expanded by means of a polished steel ball 16 of 21 mm in diameter by axially pushing it through (see arrow in FIG. 11) to an inner diameter of 2.0.79 mm. Now the pipes 14 were inserted axially symmetrically into the sleeve and the whole thing was heated to a temperature at A _F (in the present case approx. 260 ° C.). Due to the appearance of the one-way effect, a tight, firm shrink connection of the pipes 14 was achieved, which is retained even when cooled to room temperature, since the sleeve contracts at most only slightly more. The advantage of this connection using a component made of a mechanically unstable β-titanium alloy is that it can be pre-deformed at room temperature because the temperatures A _S and A _{F are} relatively high. This is not the case, for example, with Ni / Ti-based alloys. This requires pre-forming at temperatures well below room temperature, which requires special coolants and appropriate equipment. In contrast, the heating of the sleeve 13 made of titanium alloy can be accomplished in a simple manner in any workshop and also outdoors or at the assembly site by means of a blowtorch, welding torch, etc., whereby simple means (tarnishing colors, temperature chalks etc.) are sufficient for temperature monitoring.

If the connection is to be released again, the isothermal effect can be used. The shrunk-on sleeve 17 (FIG. 12) is brought to a temperature of approx. _AF plus 100 to 150 ° C., the irreversible isothermal memory effect occurring and the sleeve expanding (18 in FIG. 13). In this state, the tubes 14 can be pulled out of the sleeve 18. Should If the latter are used again, the process must be repeated from the beginning: solution annealing, quenching, pre-forming etc.

The application of the method according to the invention and the use of the components produced thereafter are not limited to the exemplary embodiments described. The component can optionally have at least one of the effects described above, for example the shape of a simple or offset leaf spring or the shape of any torsion bar and that of a cylindrical or conical coil spring. As connection or termination elements e.g. Hollow bodies, the components made of memory alloy can have a wide variety of shapes, of which FIGS. 14 to 17 show only a selection. In particular, the component can have the shape of a simple or stepped cylindrical, square, hexagonal or octagonal hollow body. Furthermore, the component can be designed as a solid or perforated cylindrical or polygonal disc provided with a bead on one or both sides.

The components made of mechanically unstable j.9 titanium alloy can be used, for example, as temperature-dependent triggering elements in electrical switches, as temperature sensors in general, as fixed or detachable connecting sleeves for pipes and rods, and as fixed or detachable seals (disk or socket shape) for ceramic components.

With the method according to the invention and the components produced thereafter, the material supply becomes so thanks to the achievement of three different memory effects how the scope of use of memory alloys expanded significantly. This is especially true for applications above room temperature (especially from 100 ° C upwards), where there is a technological gap to close. Beta titanium alloys are also characterized by good hot and cold formability and machinability. In the case of Til0V2Fe3Al there is also a commercially available alloy, which means significant economic advantages over previous conventional memory alloys based on another alloy.

Claims (20)

l. Process for the production of a component made of a titanium alloy which, in the stable initial state at room temperature, at least partially contains the body-centered cubic phase, whereby the components are mixed, melted and cast and the workpiece obtained in this way is thermoformed and solution-annealed in the temperature range of at least partial existence subjected to the stable β-phase and then quenched to room temperature and then subjected to mechanical deformation and further thermal treatment, characterized in that the metallurgical composition of the alloy belongs to the class of mechanically unstable β-titanium alloys, which are defined thereby, that its cubic, body-centered β phase can be converted at least partially into the stress-induced martensitic α "phase by applying a permanent deformation, and that the workpiece can be moved at a speed which is hoc h is enough to maintain the mechanically unstable β-phase and to suppress the formation of any new phase apart from the athermal ω-phase and a maximum of 10% by volume of thermally induced martensite by quenching, from the temperature range above the β-conversion or above a temperature high enough to at least partially cause the formation of an in turn unstable / - ⁹ phase, is quenched to a temperature at which the β phase is mechanically unstable and that the mechanical deformation in the application of tension , Pressure, shear, or a combination of at least two of these operations in the temperature range in which the β phase is mechanically unstable, such that a permanent deformation of up to a maximum of 7% is generated and that the further thermal treatment consists of at least heating. 2. The method according to claim 1, characterized in that the further thermal treatment consists in heating to a temperature above A _S , where A _{S is} the temperature at which 1/100 of the previously applied permanent mechanical deformation is reduced. 3. The method according to claim 1, characterized in that the further thermal treatment consists in heating to a temperature which is high enough to bring the oC phase to the excretion, and in holding at this temperature until at least 1 vol .-% of the original phase are converted into the α phase. 4. The method according to claim 1, characterized in that the further thermal treatment consists in heating to a temperature above A ₉₀ and a subsequent cooling to a temperature below A _S , where A _{90 is} the temperature at which the structure is at most 10 vol .-% contains martensite, and where A _{S is} the temperature at which 1/100 of the previously applied permanent mechanical deformation is reduced. 5. The method according to claim 1, characterized in that the titanium alloy contains at least one of the elements V, Al, Fe, Ni, Co, Mn, Cr, Mo, Zr, Nb, Sn, Cu. 6. The method according to claim 5, characterized in that the concentration limits expressed in atomic percentages of the alloy elements of the titanium alloy of the formula

are sufficient, where X _{i means} the concentration of the respective element in atomic percent and the coefficients A _i and B _{i are} assigned to the respective element according to the following table:

7. The method according to claim 6, characterized in that the titanium alloy belongs to the binary type and in addition to titanium 14 to 20 wt .-% vanadium or 4 to 6 wt .-% iron or 6.5 to 9 wt .-% manganese or Contains 13 to 19 wt .-% molybdenum. 8. The method according to claim 6, characterized in that the titanium alloy belongs to the ternary type and, in addition to titanium, also 13 to 19% by weight vanadium plus 0.2 to 6% by weight aluminum or 4 to 6% by weight iron plus 0.2 to 6% by weight aluminum or 15 to 2.3 wt .-% iron plus 10 to 14 wt .-% vanadium contains. 9. The method according to claim 6, characterized in that the titanium alloy belongs to the quaternary type and in addition to titanium 9 to 11 wt .-% vanadium plus 1.6 to 2.2 wt .-% iron plus 2 to 4 wt .-% Contains aluminum. 10. The method according to claim 9, characterized in that the titanium alloy consists of 10 wt .-% vanadium, 2 wt .-% iron, 3 wt .-% aluminum, the rest of titanium. 11. Component made of a titanium alloy, which in the initial state at room temperature consists of an (α + β) structure, by solution annealing above the β transition temperatures and subsequent quenching in a metastable structural state, characterized in that the alloy in its metallurgical composition Belongs to the class of mechanically unstable β-titanium alloys, which is defined as follows: - Alloy, which after solution annealing above the β-transformation temperature and subsequent quenching in ice water with a cooling time of at most 10 seconds for the passage of the temperature gradient between the β-transformation temperature and a temperature of 100 ° C and after subsequent mechanical deformation
at least partially in the voltage-induced martensitic phase can be transferred, and that the component is present in the state of stress-induced martensite in the form of the α "structure and has a memory effect after quenching by applying a permanent deformation of up to 7% due to tension, pressure, shear or a combination of these deformation states. 12. The component according to claim 11, characterized in that after heating to a temperature corresponding to the A _F point it is in the form of a β-structure and shows a one-way memory effect, where A _F denotes the temperature at which the martensite is converted back in the high temperature phase is 99% complete. 13. Component according to claim 11, characterized in that after heating to a temperature lying between the A _S and the A _F point, it is present in part in the form of α "structure and in part in the form of β structure and is a continuous two-way Memory effect shows, where A _S denotes the temperature at which 1/100 of the previously applied permanent mechanical deformation is reduced and A _F denotes the temperature at which the transformation of the martensite back into the high-temperature phase is 99% complete. 14. Component according to claim 11, characterized in that after heating to at least 50 ⁰ C above the A _F point location lying temperature and corresponding holding at this temperature, partially in the form of β-structure and partially in the form of α-structure is present and an irreversible isothermal memory shows effect, where A _F denotes the temperature at which the conversion of the martensite back into the high-temperature phase is 99% complete. 15. Component according to one of claims 12 to 14, characterized in that it has the shape of a simple or stepped leaf spring or the shape of a torsion bar or the shape of a cylindrical or conical coil spring. 16. Component according to one of claims 12 to 14, characterized in that it has the shape of a simple or stepped cylindrical, square, hexagonal or octagonal hollow body. 17. Component according to one of claims 12 to 14, characterized in that it has the shape of a full or perforated cylindrical or polygonal disc provided with a bead on one or both sides. 18. Use of a component according to claim 12 or 13 as a temperature-dependent trigger element in an electrical switch. 19. Use of a component according to claim 12 or 13 or 12 and 14 as a fixed or releasable connecting sleeve of pipes and rods. 20. Use of a component according to claim 12 or 13 as a fixed or detachable disk or sleeve-shaped seal for ceramic components.

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