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 δ_R先升高后降低, M相变温度δ_M升高, M相变热滞Δδ_M降低. 合金经300-500℃时效后, δ_R⁴⁰⁰>δ_R³⁰⁰>δ_R⁵⁰⁰. 随t_ag延长, δ_R和δ_M先快速升高后趋于稳定, Δδ_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→R→M/M→R→A (M-martensite) type occurred in the 500 ℃ annealed alloy, the A→R→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 (δ_R) of the alloy increases first and then decreases, the M transformation temperature (δ_M) increases, and the M temperature hysteresise (Δδ_M) decreases. After aging at 300-500 ℃, the δ_R⁴⁰⁰>δ_R³⁰⁰>δ_R⁵⁰⁰. With increasing t_ag, the δ_R and δ_M increase fast first and then tend to stable, and the Δδ_M decreases fast first and then tends to stable. The R temperature hysteresises in both the annealed and aged alloys are about 4 ℃.