40.3Ti 39.7Hf 15Pd 5 and Ni 40. 3Ti 44.7Hf 10Pd 5 alloys]]>

摘要

The microstructure and shape memory properties of Ni40.3Ti39.7Hf15Pd5and Ni40.3Ti44.7Hf10Pd5alloys were investigated. It was revealed that transformation temperatures of these alloys can be tailored by thermal treatments and composition alteration. Heat treated Ni40.3Ti39.7Hf15Pd5can show shape memory effect at above 100?°C. Both alloys showed shape memory effect, however, superelasticity was not observed due to the large thermal hysteresis and high rate of increase in transformation temperatures with stress. Both alloys have higher strength but considerably lower transformation strain than NiTi. Microstructure features also were investigated for grains, distribution and composition of secondary phase. It was revealed that secondary phases lead to decrease the recoverable strains of the NiTiHfPd alloys. As-received Ni40.3Ti44.7Hf10Pd5and Ni40.3Ti39.7Hf15Pd5have recoverable strains of 1.12% and 0.43% under 700?MPa, respectively.