Anomalous temperature dependence of yield stress and work hardening coefficient of B2-stabilized NiTi alloys
- Tokyo Inst. of Tech., Yokohama (Japan). Precision and Intelligence Lab.
- Tokyo Inst. of Tech. (Japan)
Yield stress and work hardening coefficient of B2-stabilized NiTi alloys are investigated using compression tests. Compositions of NiTi alloys are based on Ni-49mol.%Ti, to which Cr, Co and Al are chosen as ternary elements which reduce martensitic transformation temperatures of the B2 phase. Mechanical tests are carried out in liquid nitrogen at 77 K, air at room temperature (R.T.) and in an argon atmosphere between 473 K and 873 K. Only at 77 K, some alloys show characteristic stress-strain curves which indicate stress induced martensitic transformation (SIMT), but the others do not. Work hardening coefficient is found to be between 2 and 11GPa in all the test temperature range. The values are extremely high compared with Young`s modulus of B2 NiTi. Yield stress and work hardening coefficient increase with test temperature between R.T. and about 650 K in most alloys. The anomalous temperature dependence of mechanical properties is not related to SIMT but to precipitation hardening and/or anomalous dislocation motion similar to B2-type CoTi. Solution hardening by adding ternary elements is evaluated to be small for Cr and Co additions, and large for Al addition, depending on difference in atomic size of the ternary element with respect to Ni or Ti.
- OSTI ID:
- 571884
- Report Number(s):
- CONF-961202-; TRN: IM9806%%131
- Resource Relation:
- Conference: 1996 Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 2-6 Dec 1996; Other Information: PBD: 1997; Related Information: Is Part Of High-temperature ordered intermetallic alloys VII; Koch, C.C. [ed.] [North Carolina State Univ., Raleigh, NC (United States)]; Liu, C.T. [ed.] [Oak Ridge National Lab., TN (United States)]; Stoloff, N.S. [ed.] [Rensselaer Polytechnic Inst., Troy, NY (United States)]; Wanner, A. [ed.] [Univ. Stuttgart (Germany)]; PB: 799 p.; Materials Research Society symposium proceedings, Volume 460
- Country of Publication:
- United States
- Language:
- English
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