DE1558715B2 - ALLOYS WITH MARTENSITIC TRANSITION - Google Patents

Description

"" - ^} ORKiINAL INSPECTED

and third position elements are practically arbitrary in the aforementioned wide temperature range is selectable.

Preferably compositions of the invention Alloys are characterized in the subclaims.

In the following the invention is illustrated by means of schematic drawings of exemplary embodiments explained in more detail. It shows

F i g. 1 is a graph of the temperature range ( ⁰ C) in which the peculiar martensitic transition of the TiNi alloy occurs as a function of the atomic percent (and the weight percent) Ni,

F i g. 2 shows a graph in which for the ternary alloys TiNi ^ Co ^ a; and TiCo ^ Fej-a; the logarithm of the temperature (° Kelvin) at which the peculiar martensitic transition occurs, as Function of the concentration of "free" electrons was plotted, and

F i g. 3 shows a graph in which, for the alloys TiN ^ Co ^ - ^ and TiCo _x Fe ₁ -Z, the critical temperatures ( ⁰ K) at which the peculiar martensitic transition occurs are plotted as a function of the concentration of the "free" electrons .

The term »critical temperature« used in the following refers to the temperature in which the alloy in question shows a martensitic (diffusion-free) transition. The TiNi alloy with almost stoichiometric amounts of titanium and nickel and the related alloys of the present invention show unusual and overt, of deformation and of properties dependent on temperature. TiNi alloys show e.g. B. a mechanical memory at the critical temperature of the alloy, d. i.e., the alloys can be below the critical Temperature are deformed and then by heating to or slightly above the critical temperature return completely to their original shape, which existed before the deformation. The TiNi alloys With almost stoichiometric amounts of titanium and nickel, thermal energy can be used directly and very efficiently converting it into mechanical energy. The almost stoichiometric composition TiNi alloys have a latent heat of about 6 cal / g at the critical temperature.

Furthermore, the acoustic damping and elasticity properties and the other mechanical properties (in particular the yield point) change drastically within the temperature range in which the critical temperatures lie. The critical temperatures at which the transformations of the atomic structure take place change greatly with small changes in the alloy composition. The known alloys show a temperature maximum of 439 ° K (166 ° C) for TiNi alloys with exactly stoichiometric composition and fall to below 273 ⁰ K ⁽⁰ ° C) for TiNi alloys having slightly enriched nickel content, such as F i g. 1 shows.

While this temperature range of the martensitic transition is impressively and favorably at normal mean temperatures, even extremely small amounts of excess nickel in the binary alloy cause the formation of a second phase, namely a TiNi ₃ phase. A very small amount of the second phase of TiNi ₃ can be tolerated as well as the normal non-metallic impurities Ti ₄ Ni ₂ O, Ti ₄ Ni ₂ N, TiC, etc., but these insoluble impurities tend to contribute to the effectiveness of the TiNi alloy the behavior described above.

The task of creating alloys which show the peculiar properties of the TiNi alloy with an almost stoichiometric composition at any desired temperature within the range from absolute zero (O ⁰ K) up to temperatures above 439 ° K (166 ^{0 C),} is solved according to the invention by careful and well-considered addition of further elements according to the table, whereby the salient properties of the TiNi alloy are not reduced in their effectiveness.

When looking at the table, there are some basic structural similarities. These similarities exist primarily with regard to the ratio of the atomic radii, with regard to the valence electrons the corresponding metallic elements, with regard to the crystal structures and with regard to the electron concentrations of their intermetallic compounds. In this table the first takes into account the second and third long periods of the Periodic Table of the Elements.

Information about the elements and the intermetallic compounds built up from them Elements of the first long period of the periodic table

element atom
radius
(Ä) Ratio of
Atomic radii *) Valence-
Electrons Educated
link Crystal structure Electrons
concentration
e / atom Critical
Transition
temperature
( ⁰ K) Ti
Fe
Co
Ni 1.45+
1.24
1.25+
1.25- 1.17
1.16
1.16 4th
8th
9
10 TiFe
TiCo
TiNi Complex
a ₀ = 9Ä
asub - 2.98 Ä
Complex
G ₀ = 9Ä
a _SU b = 2.99 Å
Complex
a ₀ = 9 λ
asub - 2.98 A. 6.0
6.5
7.0 <4
35
439

element atom
radius
(A) Zr 1.59 Ru 1.32 Rh 1.35 Pd 1.37

Ratio of
Atomic radii *)

Elements of the second long period of the periodic table

Crystal structure

Valence electrons formed
link

Electron concentration

e / atom

Critical transition temperature ( ⁰ K)

1.20
1.18
1.16

4th 8th

10

ZrRu

ZrRh

ZrPd Complex
a ₀ = 9.6 Å
Q-sub - 3.2A

Complex
a ₀ = 9.6 Å
asnb = 3.2 A

Complex
α ₀ = 9.6Ä
Ä

6.0 6.5 7.0

40

653

1000

element atom
radius
(A) Hf 1.56 Os 1.33 Ir 1.35 Pt 1.39

Elements of the third long period of the periodic table

Ratio of
Atomic radii *)

Valence electrons

Formed compound crystal structure

Electron concentration

e / atom

Critical transition temperature ( ⁰ K)

1.17

1.16

1.12

10

HfOs

HfIr

HfPt Complex
α ₀ = 9.6 Å

= 3.2 Å

Complex
a _a -9.6 A

= 3.2 Å

Complex
a ₀ = 9.6 Å
Ä

6.0 6.5 7.0

*) Ratio of the atomic radius of Ti, Zr, Hf to the atomic radius of Fe, Co, Ni or Rh, Ru, Pd or Os, Ir, Pt.

Taking the natural logarithm of the transition temperatures (critical temperatures) of the compounds of the first long period, TiNi, TiCo and TiFe, and also those of the intermediate ternary alloys, ie TiNiSCo ₁ - ^ and TiCOsFe ₁ -S; plots as a function of the "free" electron concentration, one obtains the in FIG. 2 linear and smooth curve shown. From this graphical representation, which applies to the alloys formed from the elements of the first long period in the correct proportions, it follows immediately that progressively lower temperatures can be reached by replacing nickel with cobalt (TiNi- CCo ₁ -.,;), This exchange happening atom by atom. This replacement of Ni by Co in no way changes the titanium content of the ternary alloys of this series.

All ternary phases TiNizCoj-s and TiCOsFe ₁ -Z, which are formed by replacing Ni by Co and by replacing Co by Fe, show crystal structures which are similar to the underlying binary TiNi compound. The crystal structure of TiNi was determined by X-ray diffraction experiments on single crystals and crystal powder, and the occurrence of a martensitisusqo transition (without a first-order crystallographic transformation) was confirmed. Note that the number of free electrons contributed to their alloys by Ti, Fe, Co, and Ni is 4, 8, 9, and 10 (the number of electrons outside the closed shells) plots the critical temperature as a function of the free electron concentration in these alloys (number of free electrons per atom), which is shown in FIG. 3 smooth curve shown. This curve indicates that the martensitic transition observed in TiNi is not limited to this compound, but also occurs in the binary compounds of TiCo and TiFe and in the above-described ternary combinations of these elements according to the invention.

In the case of the ternary alloys according to the invention, it is which are formed by titanium and selectively varied nickel, cobalt and iron possible to achieve any desired critical temperature from almost zero degrees Kelvin up to 439 ° K reach. Selected ternary combinations of the elements Ti, Ni, Co were in the ratio TiNizCoj-s alloyed and processed into test specimens. These ternary systems practically all show the same reveal and peculiar properties like the TiNi alloy (critical temperature 439 ° K), but at one lower temperature, which in turn depends on the amount of cobalt that is used in place of nickel was introduced.

On further consideration of the table it becomes clear that the intermetallic compounds

ZrRu, ZrRh and ZrPd should behave similarly. This structural behavior should also be expected from the compounds HfOs, HfIr and HfPt of the third long period of the periodic table. Experiments have shown that the compounds of the last two series also have critical temperatures, and that they also show the same peculiar behavior that was already observed with the TiFe-TiCo-TiNi series. Furthermore, ternary substitution products, ζ. Β. ίο ZrPd ^ Rh ₁ -J; and HiPt _x Iv ₁ -X etc. are possible, which have essentially medium critical temperatures. As the table shows, the compounds of Zr and Hf and their intermediate ternary alloys according to the invention show higher critical temperatures for the atomic structure transformation that occurs. In practice, it has been achieved that the critical temperature has been extended over a range that extends approximately from absolute zero (0 ° K) to almost 1000 ° K (717 ° C). Both the yield point and the modulus of elasticity increase considerably above the critical temperature. In order to be able to benefit from the increased stiffness above the critical temperature, it is necessary to use the alloys which have critical temperatures which are below the working temperature range for a specific application. This is particularly important in self-righting structures for both hydraulic engineering and aerospace purposes. In order to achieve that such structures erect themselves in every place, such as z. B. in the sea water, it is necessary to create self righting alloys which have critical temperatures which are significantly (271 ⁰ K) are below the lower sea water temperature of about -2 ° C. To achieve this, to ensure effective mechanical memory, etc., cobalt-substituted alloys (TiNi ₂ JCo ₁ - ^) are useless.

1 sheet of GOPY drawings

209 523/229

Claims (5)

1 2 undertaken in particular to develop alloys which have this extraordinary martensitic transition at a desired temperature. Attempts to find a number of such alloy 1. To create an alloy with a martensitic surface, each with a different one transition at a desired temperature, g e k e η n temperature shows a martensitic transition, characterized by the composition have so far had little success. The reason for this lies in the fact that so far a clear understanding of the atomic structural transformation, which with the TiNi- Z, ₁₀ alloys found, unusual mecha niche and physical properties . , j .. τ .. · t> · ι. ^s i ^Q d> was missing. ^ Je n ^ to wimschten, in the range of _{the alloys based on T} i _N i, in particular O to 1000 K, the critical temperature _wdche ^ _{close to the stoichiometric} in which the martensitic transition takes place _TiNi . _{Composition of excellent} performance X an element of the ^ IV. Subgroup namhch _{an unusual and} hitherto unknown kind to fully- ^T i ^Zr ° f ^{r Hf and} Τ ™ ^d ξ J ^e ^ ^m S ^eD i ^ent ^ ^r f ^Hf > ^and Τ ™ ^d ξ J ^e ^ ^m S ^eD i ^ent ^ ^r bring. These unusual properties, such as subgroup, namely Fe, Co Ni Ru, Rh, _z _ _{R mechanical} memory, acoustic damping, Pd, Os, Ir or Pt, symbolizes and the alloy energy conversion, etc., have a completely new character to about 50 atomic percent Opened to one by X sym- _{2o Berdch yon} application possibilities. For bohsierten element and the remainder of the alloy _{höreQ m dieseQ zdt} applications by Y and Z symbolized _{elements, self-righting Luf} t _rough m-, space or consists of, the elements X, Y, Z of the same _{water components} machines bearings and machine Penode of the Periodic Table members and _facilities ^ _low Lärmentwicldung, pre- "5 * ^< . ,. , . ₁ . ,. 25 tensioned connecting elements and fastening _Od 2 emptying of claim 1 in £ reinforcing elements, tools with gespeidurch the composition _{cherter Energi6j Ene} rgieumwandler, temperaturbetä devices (switches, fire alarms, etc.), TiNi Co movements and cooling devices are just a few ^x ~ ^x 30 of the possible uses. Almost stoichiometric TiNi alloys 3. Alloy according to claim 1, characterized while sitting the aforementioned properties, they by the composition, however, have the disadvantage that they are by a relatively narrow range of the critical temperature 35 are limited. With the discovery of further connections with similar properties and their ternary intermediate alloys are now the technical properties which originally only 4. Alloy according to claim 1, characterized by the TiNi alloy, over a wide critical temperature range _{due to the composition 40.} This is especially true for combinations of the type ZrRh ^ Ru ₁ -S; TiNi ^ Co ₁ -O; and TiCo ^ Fe ₁ -K. There cobalt and iron • Items are relatively cheap and for technical 5. Alloy according to claim 1, characterized ^{purposes easily} ™ ^ ^en . ^s ™ ^{a>, they} gierungssysteme ^{for this Le} "by the composition of .45 as additives particularly suitable. The object of the present invention is to create alloys which, at a predetermined, ZrPdzRh-L-a; select within a wide temperature range show a martensitic transition 50 bar temperature. According to the invention, this object is achieved by Alloys of the composition XYsZ ₁ -Z, where depending on the desired, in the range of O to 100O ⁰ K critical temperature at which the martial "· 55 physical transition takes place, X an element of the IV. Subgroup, namely Ti, Zr or Hf and Y The present invention relates to alloy and Z each to an element of subgroup VIII, namely with a martensitic transition in Fe, Co, Ni, Ru, Rh, Pd, Os, Ir or Pt desired temperature. and about 50 atomic percent of the alloys In the past, great efforts 60 are one element symbolized by X and the rest A number of alloys have been made from alloy symbolized by Y and Z. to develop stanchions, which are the same peculiar. .-. '/ Elements, where.the elements X, Y, Z of the properties show how the stoichiometric belong to the same period of the periodic table and TiNi alloy in which the components titanium are 0 <χ <1. and nickel are available in almost equiatomic amounts are available and the US Pat. No. 3,174,851 Advantage that the critical temperature at which the has been described. This alloy is often takes place as a martensitic transition, through a partial "Nitinol" called. Great efforts have been made to assign or complete replacement of the second