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用X射线衍射、内耗、电阻和透射电镜等方法研究了等原子NiTi合金在150℃以下的相变。实验结果表明,在40—50℃之间,合金开始发生两类可逆的相变:马氏体相变和R相变。马氏体具有单斜畸变B_(19)结构,R相具有畸变B_2结构。R相变不是预转变,在-185℃,R相仍保持相对的稳定。在等原子NiTi合金中,相变依下列次序进行: β(?)β+R+M(B_(19))(?)R+M(B_(19))。
XRD, internal friction, electrical resistance and transmission electron microscopy were used to study the phase transformation of the isomorphous NiTi alloy below 150 ℃. The experimental results show that there are two types of reversible phase transitions occurred in the alloy at 40-50 ℃: martensitic transformation and R-phase transformation. The martensite has a monoclinic B_ (19) structure and the R phase has a distorted B_2 structure. R phase transition is not pre-transition, at -185 ℃, R phase remained relatively stable. In equiatomic NiTi alloys, the phase transformation is carried out in the following order: β (β) + R + M (B_ (19)) R + M (B_ (19)).