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用示差扫描量热仪和拉伸试验研究了退火温度Tan和退火时间tan对Ti-50.8Ni形状记忆合金相变和低温形变特性的影响。Tan=350～800℃时,随Tan升高,合金冷却/加热相变类型发生由A→R→M/M→R→A型向A→R→M/M→A型再向A→R/R→A型转变(A-母相,R-R相,M-马氏体),且R相变温度TR先升高后降低,M相变温度TM升高,M相变热滞ΔTM降低,R相变热滞ΔTR(约4℃)基本不变。随tan延长,400℃退火态合金的相变类型A→R→M/M→R→A保持不变,500℃退火态合金的相变类型发生由A→R→M/M→R→A型向A→R→M/M→A型转变,且TM升高,ΔTM降低,TR和ΔTR不变。600～700℃退火态合金的塑性显著大于350～550℃退火态合金。在12℃变形时,600℃以上温度退火态合金呈现SE特性,600℃以下温度退火态合金呈现SME特性。随tan延长,合金应力-应变曲线上的平台应力降低。要使Ti-50.8NiSMA在较低温度下获得SE,退火温度应在600℃以上。
The effects of annealing temperature Tan and annealing time tan on the phase transformation and low temperature deformation properties of Ti-50.8 Ni shape memory alloy were studied by differential scanning calorimeter and tensile test. When Tan = 350-800 ℃, with the increase of Tan, the type of alloy cooling / heating transformation occurs from A → R → M / M → R → A to A → R → M / M → A and then to A → R / R → A type transition (A-mother phase, RR phase, M-martensite), and R phase transition temperature TR first increased and then decreased, M phase transition temperature TM increased, M phase transition hysteresis ΔTM decreased, R phase transition hysteresis ΔTR (about 4 ℃) basically unchanged. With the increase of tan, the transformation type A → R → M / M → R → A of the as-annealed alloy at 400 ℃ remains unchanged. The phase transformation of the annealed alloy at 500 ℃ takes place from A → R → M / M → R → A Type changes to A → R → M / M → A, and TM rises, ΔTM decreases, and TR and ΔTR remain unchanged. The plasticity of annealed alloy at 600 ~ 700 ℃ is significantly greater than that of annealed alloy at 350 ~ 550 ℃. When deformed at 12 ℃, the alloy annealed at temperatures above 600 ℃ exhibited SE characteristics, and the alloy annealed at temperatures below 600 ℃ exhibited SME characteristics. As tan increases, the stress on the stress-strain curve decreases. For Ti-50.8NiSMA to obtain SE at lower temperature, the annealing temperature should be above 600 ℃.