JPS6328976B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a copper-based alloy having a shape memory effect, superelastic behavior, or vibration-proofing effect, and specifically aims to improve the characteristics of a copper-based alloy having the above-mentioned functions. Here, the shape memory effect or superelastic behavior is a phenomenon that is said to be caused by the martensitic transformation of the alloy, and the former is a phenomenon that differs between the shape at high temperature and the shape at low temperature across the transformation temperature range of the alloy. The latter phenomenon occurs when stress-induced martensite is deformed in a temperature range where it is not thermally stable. It refers to a phenomenon in which an apparently large plastic strain almost completely recovers after the deformation stress is removed. Furthermore, the vibration damping effect is an effect in which vibration energy is easily absorbed due to the contribution of martensite twins. Conventional functional alloys with shape memory effect, superelastic behavior, or vibration damping effect (hereinafter collectively referred to as functional effects) include Ni-Ti alloy, Au-Cd alloy, etc., and copper alloys such as Cu-Zn, Cu- Zn-Al
Alloys are known. However, although Ni--Ti alloys have good functional properties, they are very difficult to melt and heat-treat, so their practical range is quite limited. Furthermore, Au-Cd alloys have not been put into practical use due to the high cost of their raw materials, and remain the subject of academic research. However, copper-based alloys such as Cu-Zn and Cu-Zn-Al alloys are inexpensive raw materials and relatively easy to melt, so they are highly anticipated for future industrial use. However, these Cu-Zn and Cu-Zn-Al
The main drawbacks of copper-based alloys are as follows. That is, (1) during hot working or heating to high temperatures for imparting functionality, crystal grain size grows and functional properties tend to deteriorate. (2) There are concerns about thermal stability when used at high temperatures for long periods of time. More specifically, in order to obtain functional effects, it is preferable that the alloy material be uniform in composition, and it is necessary to perform a uniform annealing treatment at high temperatures, a hot working process in a high temperature range that does not cause eutectoid reactions, and High-temperature heat treatments such as quenching from the β-phase structure (β-ization treatment) are often used to impart functionality, and the crystal grain size may become coarse during the manufacturing process, making it difficult to control the grain size to a fine grain size. It was difficult to obtain it stably. In addition, as for the problem of thermal stability of functional alloy products, for example, in the case of shape memory effect, when an alloy that has been deformed at a temperature lower than the transformation temperature range is heated to a higher temperature,
When no load is applied, the shape almost recovers to its original shape on the high temperature side. However, if the alloy is allowed to fully or partially recover under a stress that is greater than the stress it is trying to recover from, and then is restrained, the degree of recovery will gradually decrease even after unloading, and it will not function as a shape memory alloy. There is a tendency for people to not fulfill their goals. The above is an example of a thermal stability problem in the shape memory effect, but such thermal stability problems also apply to superelastic behavior and vibration damping function. The present invention was made in view of the above-mentioned problems of Cu--Zn alloys, and aims to improve functional properties by finely stabilizing the crystal grain size and improving thermal stability. That is, the copper-based alloy of the present invention first contains Zn38
~45% by weight, Zr0.003~0.3% by weight and the balance Cu, and secondly Zn10~35% by weight.
It is characterized by containing 0.003 to 0.3% by weight of Zr, and 12% by weight or less of Al, with the remainder being Cu, which provides shape memory effects, superelastic behavior, vibration damping effects, etc. The aim is to demonstrate this. These functions depend on the alloy composition, but as described above, even alloys with the same composition have different functions depending on the operating temperature. 10 to 45% by weight of Zn in the above-mentioned copper-based alloy having shape memory effect or superelastic effect of the present invention
This is specified because if Zn is less than 10% by weight, it is difficult to have functional effects, and if it is contained in excess of 45% by weight, it will only unnecessarily impair workability and will not contribute to improving functional effects. The amount of Zn is preferably 38 to 45% by weight in the case of a Cu--Zn binary alloy as the composition of the copper-based alloy, otherwise it does not have any functional effect. Next, the reason why Zr was specified as 0.003 to 0.3% by weight is that if it is less than 0.003% by weight, the effect of improving functional properties is not sufficient, and if it is added in excess of 0.3% by weight, it will cause unnecessary dissolution and make it difficult to achieve uniformity in casting. This is because it only becomes a factor in changing the transformation temperature range, and it is difficult to expect any further improvement in functional characteristics. In addition, Al is preferably added for the purpose of controlling the transformation temperature range of the alloy according to the operating temperature range in which the above-mentioned functional effects are exhibited, but if the amount is too large, it will impede workability. It is desirable that the amount is less than % by weight. When Al is added to obtain the desired transformation temperature, it is preferable that the amount of Zn does not exceed 35% by weight, taking into consideration the workability of the alloy. In the present invention, Zr, which is added in a small amount that hardly changes the transformation temperature range, refines the crystal grains of the cast material and reduces compositional non-uniformity caused by solidification. It suppresses heterogeneous coarsening of crystal grains in processes such as processing and beta-ization treatment to impart functionality, and improves ductility. It improves it. Furthermore, it contributes to thermal stabilization of the alloy and improves the practical properties of the copper-based alloy. The present invention will be explained in detail below with reference to Examples. Example 1 Ordinary electrical copper metal, electrolytic zinc, electrolytic tin, purity
A 20 mmφ copper-based alloy having the composition shown in Table 1 was melted and cast in an argon gas atmosphere using 99.99% aluminum, Cu-30% Zr master alloy, Cu-15% Si master alloy, etc. After homogenizing this at 800℃ for 5 hours,
Rolled to 1mm ^t by hot rolling and cold rolling,
The surface was then lightly mechanically polished to approximately 100 mm.
It was made into a length of tape. This tape was water-quenched at 700°C in a straight state to obtain a sample for functional effect investigation. During this period, we observed the cross-sectional macrostructure of the cast ingot and observed its workability. The functional effects of the samples were also investigated, and the results are shown in Table 2.

【table】

【table】

【table】

[Table] From Table 2 above, it was found that the alloy of the present invention has a finer casting structure and superior workability than the comparative alloy. It was found that even if Zr is contained, if it is added in excess as in Alloy No. 10, it has a negative effect on the functional properties. Example 2 Using the samples exhibiting the shape memory effect prepared in Example 1, the thermal stability of the shape memory function in these alloys was investigated. The test method was to bend the sample 180° at room temperature to form a U-shape along a 25mmφ cylinder (i.e., radius of curvature 12.5mm), restrain it, and leave it immersed in an oil bath at a predetermined temperature before recovering. was investigated by measuring its radius of curvature. The results are shown in Table 3, and it was found that the alloy of the present invention was superior in thermal stability compared to comparative alloys having similar transformation temperature ranges.

【table】

[Table] As detailed above, the copper-based alloy of the present invention is Zn10
~45 wt% and 0.003~0.3 wt% Zr or Al
It is a copper-based alloy with shape memory effect or superelastic effect characterized by containing 12% by weight or less of Cu, and the balance being Cu, and as a result of improved ductility due to refinement of crystal grains, it is easy to process. It has a remarkable effect of improving properties and thermal stability, so it has great effects when used industrially.

Claims (1)

[Claims] 1. A copper-based alloy having a shape memory effect or a superelastic effect, characterized by containing 38 to 45% by weight of Zn, 0.003 to 0.3% by weight of Zr, and the remainder being Cu. 2 Zn10-35% by weight, Zr0.003-0.3% by weight and
A copper-based alloy having a shape memory effect or a superelastic effect, characterized by containing Al in a range of 12% by weight or less, and the balance being Cu.