Stress-Induced Martensitic Transformation of Boundary gamma-Fe Particles in Cu

在Cu-Fe合金双晶的小角边界上引入了大的相干γ - fe粒子。在548K温度下采用晶界滑动应力或在77K温度下直接施加外部应力，研究应力诱导马氏体从fcc到bcc的转变。在这些加载过程中，没有由于晶体位错活动而产生塑性变形。较大的颗粒冷却到77K或受到77K的外部应力时转变为bcc。一些特殊的马氏体变体在边界滑动引起的内应力下优先形成，或取决于施加应力的意义（拉或压）和方向（[416]_f或[001]_f）。假设应力有助于原子的剪切运动使晶格从fcc变为bcc，可以很好地解释变异体的优先形成。由于γ - fe和Cu之间的晶格参数差异而引起的较大的预先存在的静水应力对转变没有加速作用，这也与这一论点一致。应力对整体形状应变的任何影响已被排除在外。

Large coherent gamma-Fe particles were introduced on a small-angle boundary in bicrystals of Cu-Fe alloys. They were stressed by grain-boundary sliding at 548K or directly by external stress at 77K to study the stress-induced martensitic transformation from fcc to bcc. No plastic deformation due to crystal dislocation activity occurred during these loading processes. Larger particles transformed to bcc when they were cooled to 77K or were stressed by the external stress at 77K.Some particular variants of martensite were preferentially formed under the internal stress caused by boundary sliding or depending on the sense (tension or compression) and direction ([416]_f or [001]_f) of the applied stress. The preferential formation of the variants could be explained well by postulating that the stress helps the shear movement of atoms to change the lattice from fcc to bcc. No accelerating effect of a large pre-existing hydrostatic stress, caused by the lattice parameter difference between gamma-Fe and Cu, on the transformation is also consistent with this contention. Any effect of the stress on the overall shape strain has been excluded.