Metal articles having a property of repeatedly reversible shape memory effect and a process for preparing the same

Claim 2

A process for preparing metal articles having a property of repeatedly reversible shape memory effect, comprising applying deformation stress to a β-brass type martensitic Ni-Al alloy consisting essentially of 55 -65 at % of Ni and the remainder of Al at a temperature below Md point, in which the value of said deformation stress is within a range exceeding the first yield point of martensite crystal in said alloy beyond easy plastic flow region but below the point at which a large amount of permanent strain is produced by glide deformation.

Claim 3

A process as claimed in claim 1, comprising applying said deformation stress to said alloy at a temperature below Ms point.

Claim 4

A process as claimed in claim 1, comprising applying said deformation stress to said alloy at a temperature below Mf point.

Claim 5

A process as claimed in claim 1, in which prestrain is preliminarily applied to said alloy in a different direction from that of the final deformation.

Claim 6

A process as claimed in claim 4, in which the prestrain amount is below 5%.

Claim 7

A process as claimed in claim 1, in which said Ni-Al alloy is a coarse grained or single crystal alloy.

Claim 8

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 1.

Claim 9

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 5.

Claim 10

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 6.

Claim 11

A process for preparing coarse grains or single crystal of β-brass type (Ni, Co) Al alloy having the composition range as shown in FIG. 2 of the appended drawings, comprising the steps of melting starting material having said composition in a vacuum or an appropriate atmosphere, solidifying slowly the melt for promoting the formation of coarse grains or single crystals in β'-phase of the alloy, homogenizing the ingot at about 1100°-1400° C for a few days, and heat-treating the coarse grains or single crystals obtained from the ingot at a temperature below the melting point of the alloy and then rapidly cooling the same.

Claim 12

A process for preparing coarse grains or single crystal of β-brass type (Ni, Co) Al alloy having the composition range as shown in FIG. 2 of the appended drawings, comprising the steps of melting starting material having said composition in a vacuum or an appropriate atmosphere, solidifying slowly the melt for promoting the formation of coarse grains or single crystals in β'-phase of the alloy, homogenizing the ingot at about 1100°-1400° C for a few days, and heat-treating the coarse grains or single crystals obtained from the ingot at a temperature below the melting point of the alloy and then rapidly cooling the same.

Claim 13

A process as claimed in claim 1, in which prestrain is preliminarily applid to said alloy in a different direction from that of the final deformation.

Claim 14

A process as claimed in claim 11, in which the prestrain amount is below 5%.

Claim 15

A process for preparing metal articles having a property of repeatedly reversible shape memory effect, comprising applying deformation stress to a β-brass type martensitic Ni--Al--Co alloy having a composition range as shown in FIG. 2 of the appended drawings at a temperature below Md point, in which the value of said deformation stress is within a range exceeding the first yield point of martensite crystal in said alloy beyond easy plastic flow region but below the point at which a large amount of permanent strain is produced by glide deformation.

Claim 16

A process for preparing metal articles having a property of repeatedly reversible shape memory effect, comprising applying deformation stress to a β-brass type martensitic Ni--Al--Co alloy having a composition range as shown in FIG. 2 of the appended drawings at a temperature below Md point, in which the value of said deformation stress is within a range exceeding the first yield point of martensite crystal in said alloy beyond easy plastic flow region but below the point at which a large amount of permanent strain is produced by glide deformation.

Claim 17

A process as claimed in claim 13 comprising applying said deformation stress to said alloy at a temperature below Ms point.

Claim 18

A process as claimed in claim 13 comprising applying said deformation stress to said alloy at a temperature below Mf point.

Claim 19

A process as claimed in claim 13, in which prestrain is preliminarily applied to said alloy in a different direction from that of the final deformation.

Claim 20

A process as claimed in claim 16, in which the prestrain amount is below 5%.

Claim 21

A process as claimed in claim 13, in which said alloy is a coarse grained or single crystal alloy.

Claim 22

A process as claimed in claim 18, in which prestrain is preliminarily applied to said alloy in a different direction from that of the final deformation.

Claim 23

A process as claimed in claim 19 in which the prestrain amount is below 5%.

Claim 24

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 12.

Claim 25

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 13.

Claim 26

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 17.

Claim 27

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 18.

Claim 28

A metal article having a property of providing a repeatedly reversible shape memory effect prepared by the process of claim 20.