Method of manufacturing high-temperature shape memory alloys

• US 5,641,364 A
• Filed: 10/27/1995
• Issued: 06/24/1997
• Est. Priority Date: 10/28/1994
• Status: Expired due to Term

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Golberg, Dmitrii Victorovich, Mitose, Kengo, Otsuka, Kazuhiro, Horikawa, Hiroshi, Ueki, Tatsuhiko
• Primary Examiner(s): WYSZOMIERSKI, GEORGE P
• Application Number:
  US08/549,319
• Time in Patent Office: 606 Days
• Field of Search: 148/402, 148/563, 148/407, 148/409, 148/421, 148/426
• US Class Current: 148/563
• CPC Class Codes: C22F 1/006 Resulting in heat recoverable alloys with a memory effect

Abstract

A method of manufacturing a high-temperature shape memory alloy includes the steps of cold-working a high-temperature shape memory alloy, in which a reverse martensite transformation start temperature (As) in a first heating after cold working reaches 350° C. or above. Thereafter, the cold-worked alloy undergoes a first heat treatment for a period of time within the incubation time required for recrystallization or less, and at a temperature higher than a reverse martensite transformation finish temperature (Af). Finally, the resultant alloy is annealed with a second heat treatment, at a temperature which is not less than the plastic strain recovery temperature and not more than the recrystallization temperature. Specifically, the first heat treatment is performed for a period of three minutes or less at a temperature which exceeds 500° C. and which is lower than the melting point of the alloy. The composition of the high-temperature shape memory alloy is Ti₅₀ Ni_50-x Pd_x (x being 35 to 50 at %), Ti_50-x Ni₅₀ Zr_x (x being 22 to 30 at %), Ti_50-x Ni₅₀ Hf_x (x being 20 to 30 at %) or the like.

Claims

1. A method of manufacturing a high-temperature shape memory alloy, comprising the steps of:

cold-working a high-temperature shape memory alloy, so that a reverse martensite transformation start temperature (As) of the alloy reaches 350°

C. or above and a reverse martensite transformation finish temperature (A_F) of the alloy exceeds the recrystallization temperature of the alloy;

thereafter subjecting the cold-worked alloy to a first heat treatment at a first temperature above the recrystallization temperature, for a period of time sufficiently short to prevent the start of recrystallization, said first temperature being higher than the A_f temperature; and

then

annealing the resultant alloy in a second heat treatment, at a second temperature which is not less than the plastic strain recovery temperature of the alloy and not more than the recrystallization temperature of the alloy.

2. A method of manufacturing a high-temperature shape memory alloy according to claim 1, wherein the first heat treatment is performed for a period of three minutes or less and wherein said first temperature exceeds 500°

C. and is less than a melting point of the alloy.

3. A method of manufacturing a high-temperature shape memory alloy according to claim 1, wherein the composition of said high-temperature shape memory alloy is expressed, with numerical values representing at %, as Ti₅₀ Ni_50-x Pd_x, in which X is 35 to 50 at %, Ti_50-x Ni₅₀ Zr_x, in which X is 22 to 30 at %, or Ti_50-x Ni₅₀ Hf_x, in which X is 20 to 30 at %.