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用示差扫描量热仪研究了退火和时效工艺对Ti-50.8Ni-0.3Cr(原子分数,%)低温超弹性合金相变行为的影响,结果表明,350-450℃退火态Ti-50.8Ni-0.3Cr合金冷却/加热时发生A→R/R→A型可逆相变,500℃退火态合金发生A→R→M/M→R→A型相变,550-600℃退火态合金发生A→R→M/M→A型相变,650℃以上退火态合金不发生相变.退火时间对合金相变行为影响不大.随时效时间t_(ag)延长,300℃时效态合金的相变类型保持为A→R/R→A,400℃时效态合金发生由A→R/R→A向A→R→M/M→R→A转变,500℃时效态合金发生由A→R→M/M→R→A向A→R→M/M→A转变,随退火温度升高,合金的R相变温度θ_R先升高后降低,M相变温度θ_M升高,M相变热滞△θ_M降低.合金经300-500℃时效后,θ_R~(400) >θ_R~(300) >θ_R~(500).随t_(ag)延长,θ_R和θ_M先快速升高后趋于稳定,△θ_M先快速降低后趋于稳定,退火和时效态合金的R相变热滞均在4℃左右.

The effects of annealing and aging processes on transformation behavior of the low-temperature superelasticity alloy Ti-50.8Ni-0.3Cr (atomic fraction, %) were investigated with differential scanning calorimetry. The A→R/R→A (A-parent phase, R-R phase) type reversible transformation occurred in the 350-450 ℃ annealed alloy upon cooling/heating, the A→RM/ M→R→A (M-martensite) type occurred in the 500 ℃ annealed alloy, the AR→M/M→A type occurred in 550-600 ℃ annealed alloy, and no transformation occurred in the above 650 ℃ annealed alloy. The effect of the annealing time on transformation behavior of the alloy is not serious. With increasing aging time t_(ag), the transformation type of 300 ℃ aged alloy still is A→R/R→A, the one of 400 ℃ aged alloy changes from A→R/R→A to A→R→M/M→R→A, and the one of 500 ℃ aged alloy changes from A→R→M/M→R→A to A→R→M/M→A. With increasing annealing temperature,the R transformation temperature (θ_R) of the alloy increases first and then decreases, the M transformation temperature (θ_M) increases, and the M temperature hysteresise (Aθ_M) decreases.After aging at 300-500 ℃, the θ_R~(400)>θ_R~(300)>θ_R~(500). With increasing t_(ag), the θ_R and θ_M increase fast first and then tend to stable, and the △θ_M decreases fast first and then tends to stable. The R temperature hysteresises in both the annealed and aged alloys are about 4 ℃.