晶体取向对铝单晶在循环形变过程中的应力响应、摩擦应力和反馈应力的影响

EFFECT OF ORIENTATION ON STRESS RESPONSE, FRICTION STRESS AND BACK STRESS DURING CYCLIC DEFORMATION IN AI SINGLE CRYSTALS.

采用晶体取向不同的99.999％Al单晶试样,进行拉压对称的应变控制疲劳试验。应变幅为2×10^(-3)。记录了各循环周次的应力、应力-应变滞后回线,根据回线的面积和形状计算了循环形变中的能量损耗、摩擦应力、反馈应力及形状参量。观察了滑移形貌,发现晶体取向对上述各量均有很大影响。多滑移取向晶体比单滑移取向晶体具有大得多的初始硬化率、饱和应力值和能量损耗。而滞后回线的形状则后者较接近矩形,其形状参量V_H比前者大,探讨了各参量间的关系及它们与材料内部位错结构的联系。

The symmetrical push-pull fatigue tests at strain of 2×10^(-3) for different slip orientation A1 single crystals, 99.999% purity, were carried out at room temperature in air on 5 kN Shimadsu 4825 servo-hydrauhc machine. The peak stresses of various cycles were measured by a digit voltmeter and the stress-strain hysteresis loops for selected cycles were recorded using an X-Y recorder. The energy losses, friction stresses, back stresses and shape parameters of hysteresis loops were measured from the hysteresis loops obtained. The morphology of fatigued specimen surfaces was observed under SEM. The results found that the parameters above are affected awfully by the orientation of crystals. The crystals with multiple.slip orientation, in comparison with single one, are of numerous initial hardenability, saturated stresses and energy losses, while the hysteresis loops shape of single slip orientation crystals become even more rectangular. The relation among parameters above mentioned and contact between them and internal structure of the materials were discussed in belief.