摘要
发现经不同热处理(固溶热处理及时效)工艺的近等原子Ni-Ti合金试样在冷却时会出现不同的相变顺序:除B_2(母相)→I(无公度相)→R相→M(马氏体相)及B_2→M外,在I相之前、R相之前或R→M之前,都会产生B2→M。提高固溶化温度使母相富Ni,从而使Ms^(B_2→M)及T_R下降,但形成等原子有利有序化。母相有序化使T_R升高,Ms^(R→M)下降。时效中发生有序化及沉淀两个过程。固溶化温度的提高,在700～750℃先使T_R上升,在750℃以上则下降。无公度相变也可能由原子面位移凝结所驱动。R相变有利于形状记忆效应,文中提出了可能的解释。R相对双程形状记忆效应约贡献1/3。
There may appear various phase transition orders upon cooling in specimens of nearly equal tomic alloy after different heat treatment processes(solutionization and aging), i. e. B_2(parent)→I(Incommusurate)→Rphase→M(martensite) and B_2→M, in addition, B_2→M may occur before theappearance of the incommusurate phase, R phase or R→M. Increasing the solutionization temperature causes increasing the Ni-content in the parent phase that leads decreasing M_s^(B_2→M) and T_R, however, the formation of equal atomic concentration promotes the ordering of the parent phase and T_R raises and M_S^(R-M) lowers with the increase of the ordering degree of the parent phase. Ordering and precipitation processes occur upon aging. T_R increases as the solutionization emperature increases from 700 to 750℃ and lowers upon solutionization at temperatures above 750℃. The incommusurate transition may be driven by the condensation of the displace of the atomic planes. The R phase transition is beneficial for the shape memory effect and the possible explanation is discussed. The R phase contributes about 1/3 of the two-way shape memory effect.
