热处理对Ti-Ni-Cr低温超弹性合金相变行为的影响
摘要
The effects of annealing and aging processes on transformation behavior of thelow-temperature superelasticity alloy Ti-50.8Ni-0.3Cr(atomic fraction,%) were investigated withdifferential scanning calorimetry.The A→R/R→A(A-parent phase,R-R phase) type reversibletransformation 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 typeoccurred in 550-600℃annealed alloy,and no transformation occurred in the above 650℃annealedalloy.The effect of the annealing time on transformation behavior of the alloy is not serious.Withincreasing aging time t_(ag),the transformation type of 300℃aged alloy still is A→R/R→A,the one of400℃aged alloy changes from A→R/R→A to A→R→M/M→R→A,and the one of 500℃aged alloychanges 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 Mtransformation temperature(θ_M) increases,and the M temperature hysteresise(△θ_M) decreases.After aging at 300-500℃.theθ_R~(400)θ_R~(300)θ_R~(500).With increasing t_(ag),theθ_R andθ_M increase fast firstand then tend to stable,and the△θ_M decreases fast first and then tends to stable.The R temperaturehysteresises in both the annealed and aged alloys are about 4℃.