JPH048494B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a copper-based shape memory alloy having shape memory effect, superelastic behavior, and vibration damping effect, and more specifically, to improve the workability and fatigue properties of the above alloy. It is something. <Prior art> In general, shape memory effect and superelastic behavior are phenomena that are said to be caused by the mantensite transformation of an alloy, and the former is a phenomenon that occurs between the transformation temperature range of an alloy and the shape at a high temperature and the shape at a low temperature. This refers to the appearance of a unidirectional or reversible shape restoration phenomenon between the shape on the side, and the latter is the phenomenon in which stress-induced mantensite deforms in a temperature range where it is not thermally stable. It sometimes appears, and refers to a phenomenon in which an apparently large plastic strain almost completely recovers after the deformation stress is removed. Furthermore, in this case, the vibration damping effect is an effect in which vibration energy is easily absorbed due to the movement of mantensite twin boundaries. The above-mentioned shape memory effect, superelastic behavior, and vibration damping effect are collectively referred to as "functional effect", and alloys having this functional effect are hereinafter referred to as "shape memory effect, shape memory having superelastic behavior, and vibration damping effect". "alloy". Conventionally, Ni-Ti alloy, Au-
In addition to Cd alloys, copper alloys such as Cu−Zn and Cu−
Zn-Al alloys are known. <Problem to be solved by the invention> However, although the above Ni-Ti alloy has good functional properties, it is extremely difficult to melt, process, and heat treat it, and the raw material metal is also expensive. Products also became expensive, and the range of practical use was inevitably limited. Furthermore, Au-Cd alloys have poor mechanical properties, are expensive raw materials, and are difficult to handle because Cd is toxic, so they have not been put into practical use and remain the subject of academic research. On the other hand, copper-based shape memory alloys such as Cu-Al and Cu-Zn-Al alloys are inexpensive raw materials and relatively easy to melt, so they are highly expected to be used industrially in the future. . However, the following main drawbacks have been pointed out to these copper alloys. That is, polycrystalline materials that can be easily produced industrially do not necessarily have sufficient material properties such as ductility, and are prone to breakage when large strains are applied. There is also a desire for improvement in terms of fatigue strength during repeated use. The problem with these polycrystals is that even though they are alloys with the same composition, single crystals have excellent mechanical properties, so they suffer from brittle grain boundaries, the shape memory effect mentioned above, and superelastic behavior. In order to obtain a shape memory alloy with anti-vibration effects, the manufacturing process requires homogenizing annealing at high temperatures to make the composition uniform.
There are many hot working processes and high-temperature heat treatments such as quenching from the β-phase structure (β-ization treatment) to impart functionality, and the crystal grain size often becomes coarse during the manufacturing process, but isotropic properties cannot be improved. It is more advantageous to make the particles finer, and this is also thought to be the cause. This invention was made in order to solve the above-mentioned conventional problems, and is a copper-based shape memory that can improve ductility and fatigue properties without impairing the shape memory effect, superelastic behavior, and vibration damping effect. The purpose is to provide alloys. <Means for Solving the Problem> That is, the copper-based shape memory alloy of the present invention first contains 8 to 18% by weight of Al, 0.05 to 3% by weight of V, and the balance
It is characterized by being made of Cu, and the second is Al2 to 18% by weight, V0.05 to 3% by weight, and further Fe, Co, Ni,
The alloy contains one or more of the metals Si, Sn, Ag, Mg, Mn, Sb, Ga, Ge, and In within the range that allows the alloy to have a β-phase structure, and the remainder is Cu. This is a feature that is intended to exhibit all of the shape memory effect, superelastic behavior, and vibration damping effect. These functions can be used for various functional purposes even if the alloy has the same composition depending on the alloy composition and the temperature at which it is used. <Function> In the copper-based shape memory alloy of the present invention, the Al content is specified as 2 to 18% by weight. If the Al content is less than 2%, there will be little improvement in strength, and the transformation temperature range will be too low. This is because it is generally too low to exhibit the shape memory effect at temperatures near room temperature (e.g. -50 to 100°C), and adding more than 18% will only unnecessarily impair processability. This is because it does not have the effect of further improving functional properties. The amount of Al is determined as the composition of the functional alloy.
In the case of a Cu-Al binary alloy, the content is preferably 8 to 18% by weight, and other than that it is difficult to have any functional effect. Next, the amount of V was specified as 0.05 to 3% by weight.
If it is less than 0.05% by weight, the effect of improving functionality will not be sufficient, and if it is added in excess of 3% by weight, it will only cause unnecessary dissolution and make it difficult to achieve uniformity in casting, and further improvement in functional properties cannot be expected. This is because it is difficult. In addition, in this invention, Fe, Co, Ni, Si, Sn, Ag, Mg,
It is also effective to contain one or more of the metals Sb, Ga, Ge, and In within a range that allows the alloy to have a β-phase structure. Here, the range in which the alloy can have a β-phase structure is specifically Fe: 0.1 to 4.5% by weight, Co: 0.1%
~6.0 wt%, Ni: 0.1~7.0 wt%, Si: 0.05~5.5
Weight%, Sn: 0.01-9.0% by weight, Ag: 0.01-3.0% by weight, Mg: 0.1-8.0% by weight, Mn: 0.1-5.0% by weight, Sb: 0.05-5.0% by weight, Ga: 0.01-3.5% by weight , Ge: 0.01-3.0% by weight, In: 0.01-5.5% by weight
It is preferable that V added in this invention hardly changes the transformation temperature range of the alloy depending on its content,
In addition to improving brittleness at grain boundaries, it also suppresses coarsening of grain size during various heat treatments in the manufacturing process, improves the ductility and fatigue strength of polycrystalline alloys, and improves properties in practical use. It also improves workability during manufacturing. As described above, this invention refines the crystal grains of the cast material by adding a small amount of V, without substantially changing the transformation temperature range of the Cu-Al alloy, and further homogenizes, hot-works, and It is characterized by suppressing the growth of crystal grains during the heating process for beta-ization treatment, which can prevent brittle fractures at grain boundaries during use or processing of the alloy. Therefore, the functional properties and processability of polycrystalline alloy materials, which are advantageous for industrial use, are significantly improved. <Examples> The present invention will be explained in detail below using examples. Example 1 Ordinary electrical copper ingot, 99.99% pure aluminum, electric tin, Cu-30%V master alloy, and Cu-15
A 20 mm diameter copper alloy having the composition shown in Table 1 was melted and cast using a %Mn master alloy etc. in an argon gas atmosphere. After uniformly annealing this at 800℃ for 5 hours,
The tape was hot rolled to a thickness of 1 ^mm , and then its surface was lightly mechanically polished to obtain a tape approximately 100 mm long. This tape was water-quenched at 800°C in a straight state to obtain a sample for functional effect investigation. During this period, we also observed the processability. The functional effects of the samples were also investigated, and the results are shown in Table 2.

【table】

【table】

[Table] From Table 2 above, the alloy of the present invention has good functional properties such as shape memory effect and superelastic effect, and in particular, the Cu-Al binary alloy has a lower transformation temperature range and an increased Al content. It is recognized that the effect is particularly large in such cases. It was also confirmed in cold rolling tests that the ductility was improved compared to the comparative alloys. It was also found that even if V was added in excess, as in Alloy No. 11, it had a negative effect on the functional properties. Example 2 Using the samples exhibiting the shape memory effect prepared in Example 1, the mechanical properties and grain size of these alloys were investigated, and the results are shown in Table 3.

【table】

[Table] From Table 3 above, it can be seen that the mechanical properties of the alloy of the present invention are greatly improved in both tensile strength and elongation at break, and the crystal grain size is also refined. In addition, as a result of observing the fracture surfaces of the specimens after the tensile test, comparative alloys Nos. 7 to 11 were all fractured at grain boundaries, but alloys Nos. 1 to 6 of the present invention showed signs of transgranular cracking. It was exhibiting. Example 3 Among the alloys shown in Table 1 of Example 1, the fatigue life of the invention alloy No. 3 and comparative alloy No. 9, which have similar transformation temperature ranges, was investigated using an oscillating tensile tester. As a result, we obtained the results shown in Table 4.

[Table] From Table 4 above, it can be seen that the fatigue properties of the alloys of the present invention are improved compared to comparative alloys having similar transformation temperature ranges. <Effects of the Invention> As detailed above, the copper-based shape memory alloy of the present invention essentially contains Al2 to 18% by weight and V0.05 to 3% by weight, or further contains Fe, Co, Ni,
The alloy contains one or more of the metals Si, Sn, Ag, Mg, Mn, Sb, Ga, Ge, and In within the range that allows the alloy to have a β-phase structure, and the remainder is Cu. As a result of improved ductility due to the effect of improving the brittleness of grain boundaries and the refinement of crystal grains, a remarkable improvement effect is obtained in workability, and fatigue properties are also significantly improved. It has great effects when used industrially.

Claims (1)

[Claims] 1 Contains 8 to 18% by weight of Al and 0.05 to 3% by weight of V,
A copper-based shape memory alloy characterized by the remainder being Cu. 2 Al2~18% by weight, V0.05~3% by weight and Fe,
Co, Ni, Si, Sn, Ag, Mg, Mn, Sb, Ga,
The alloy contains one or more of Ge and In to the extent that it can have a β-phase structure, and the remainder is
A copper-based shape memory alloy characterized by being made of Cu.