前言通常的金属(包括合金),在拉伸或弯曲等外部应力作用下,不论变形难易都要发生变形应变。如果超过弹性极限,其变形应变在去除外力之后也不恢复,当然在改变温度时也不恢复。这样的变形叫做塑性变形。这种变形是通过金属晶体内的位错在外部应力作用下沿滑移面运动而脱出晶体表面的方位进行的。位错的运动是不可逆的,因此,金属一旦发生了变形,不管是去掉外力还是改变温度,当然都不能使其形状 Foreword The usual metal (including alloys), in the tensile or bending under the effect of external stress, regardless of the deformation is difficult to deformation and strain. If the elastic limit is exceeded, the deformation strain will not recover after the external force is removed, and certainly will not be restored when the temperature is changed. This deformation is called plastic deformation. This deformation is carried out by the dislocations within the metal crystal under the action of external stress along the sliding surface movement out of the crystal surface orientation. Dislocation movement is irreversible, so once the metal has been deformed, whether it is to remove the external force or change the temperature, of course, can not make its shape