JPS60187648A - High-temperature memory alloy - Google Patents

Abstract

PURPOSE:To develop an alloy having shape memory and superelastic characteristics in a high temp. region by molding and sintering powder consisting of a specifically composed Cu-Al-Ni alloy. CONSTITUTION:A Cu-Al-Ni alloy consisting of 12-14wt% Al, 1-5wt% Ni and the balance Cu is melted and is cast to an ingot. The ingot is ground at a room temp. and is pulverized to about 100 microns. The pulverous powder is molded at cold and is sintered for 2hr at 900 deg.C in the atm. The sintered molding is swaged to a bar shape at 900 deg.C and the bar is machined to manufacture a test piece. The test piece is subjected to a solution heat treatment at 900 deg.C in an Ar gaseous atmosphere then to oil hardening. The so-called high-temp. memory alloy which has 10-100 micron crystal grain size, is deformed at 200 deg.C and restores the shape before the deformation when reheated to 350 deg.C is produced from an inexpensive raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an alloy having thermal martensitic transformation characteristics, and in particular, an alloy having the above-mentioned characteristics in the temperature range from room temperature to 35 ltl. This invention relates to a steel-aluminum-nickel high-temperature memory alloy whose crystal grains are refined and its toughness is completely increased by manufacturing C1 using a metallurgical method.

[Prior art and problems with f:]

In recent years, intermetallic compounds have been recognized as materials with attractive properties.
Among these materials, there are alloys that exhibit unique mechanical properties called shape memory and superelasticity (rubber elasticity).Currently, about 10 types have been discovered, as shown in Table 1 The upper limit of the temperature that exhibits this type of property is about 100℃ at most, and considering cost and processability, the material that can be expected to be put into practical use is Nl-Ti. (Product name: Nitinol 1.
There are about two types of cu-Zn k1 alloy gold. For this reason,
There has been a strong desire to develop a memory alloy that can be used in a wider temperature range, is low cost, and has good workability.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and the upper limit of the temperature at which the thermoelastic martensitic transformation characteristics can be obtained is higher than that of the conventional one.
The present invention aims to provide a high temperature memory alloy gold which is higher than 00C, is low cost and has good workability.

[Summary of the invention]

The present invention uses low-cost aluminum 12 to 14 tit
91; .

A master alloy consisting of nickel 1 to 5-weight IT with the remaining main component copper is cast, and the alloy is then crushed, mixed, sintered, and hot plastic worked to produce an alloy that produces aluminum oxides during sintering. [Effects of the Invention] The present invention is a high-temperature memory alloy that suppresses coarsening of crystal grains, increases cold workability, and reduces the amount of aluminum used compared to conventional materials. It is characterized by an increased temperature of F-forming with martensitic transformation characteristics to 350°C, and is non-magnetic, highly corrosion resistant, and has excellent resistance to leaping and thermal stability at high temperatures. It also has the characteristics C.

This point ff:C is explained in more detail in Figure 1.
When the alloy of the above composition according to the present invention is produced by normal melting and rolling followed by hot plastic working, the crystal grains easily grow coarsely to O8l or more, and when no external force is applied to the alloy, the crystal grains easily grow coarsely. When deformed at a temperature higher than the transformation temperature Ttr and under a tensile stress F, no ductility occurs and wall fracture occurs easily in the elastic region. however.

Some ductility exists under compressive stress and under tensile or compressive stress in the temperature range below the transformation temperature Ttr when no external force is applied. Further, the transformation temperature Ttr when an external force is applied and no carbon is applied increases as the amount of aluminum decreases, and reaches a maximum temperature of 200 to 250°C. On the other hand, in the alloy having the composition according to the present invention and produced by powder metallurgy, an oxide of aluminum is generated during sintering, and this oxide suppresses coarsening of crystal grains. The crystal grain size is as fine as several tens of microns, and when an external force is applied to this alloy, the transformation temperature is Ttr.

Ductility also occurs when deformed under tensile stress at temperatures higher than . C
The maximum transformation temperature Ttr when no external force is applied is 2.
00 to about 2500, and under tensile stress,
Unlike alloys manufactured by the melting method, they do not require special consideration to avoid tensile stress when used, nor do they need to be made into single crystals to avoid grain boundary cracking, making them easy to use. It is a material that can be manufactured into high-temperature devices easily.

It is an extremely useful alloy that can be processed into parts for high-temperature equipment.

[Embodiments of the invention]

The present invention will be explained below using examples.

Aluminum weighs 12.8 and nickel weighs 4.0.

The alloy, the remainder of which was copper, was melted in a vacuum and cast into a mold to create an involatra. The ingot thus produced was crushed at room temperature to create a powder with a particle size of about 10 microns, which was then mixed, cooled and molded, and sintered in the air at 900°C for 2 hours1, followed by swaging processing at 900°C. A rod-shaped ingot was created. Then, slice it by cutting to make a complete C test piece, and heat it at 900℃ in an argon atmosphere.
After solution treatment for 1 hour, it was quenched in rapeseed oil at room temperature. The grain size of the alloy at this point was about 30 microns IJt. Then, using an Instron type tensile tester, tensile deformation was performed at C300℃ and 200℃ to give an appropriate deformation tt, and then the load was unloaded. Now transform:
After unloading, some strain remained, but by reheating to 300°C, the shape recovered to the shape before deformation, exhibiting so-called shape memory properties. As described above, the memory alloy of the present invention has been shown to exhibit shape memory and superelastic properties even at high temperatures and under tensile stress, and it would be extremely effective to apply this to high-temperature devices and parts for high-temperature equipment.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the deformation behavior of molten material and sintered material during tensile and compressive deformation at transformation temperature Ttr when no external force is applied, at temperatures lower than Ttr, and at temperatures higher than that. Figure 2 shows the copper-12,8i196' aluminum-4.0% by weight nickel powder sintered alloy at 300°C according to the present invention.
Characteristic diagram of tensile deformation at . Figure 3 shows the amount of nickel powder sintered alloy added to copper-12,8ii (,141 aluminum-4,0 weight) according to the present invention.
It is a characteristic diagram showing tensile deformation characteristics at 00°C and temperature-strain characteristics when reheated at 300°C after unloading. Table 1. Superelasticity and shape memory materials 1st factor (Ttr, 'lh\i1t*q□rN+ t;

Claims (1)

[Claims] Aluminum 12-14 weight, nickel 1-5 weight 11
96', the remaining main component is copper, 10-100
A high-temperature memory alloy characterized by having a micron grain size structure.