高纯铝单晶在拉压疲劳早期过程中的行为

BEHAVIOUR OF AI-SINGLE CRYSTAL DURING EARLY STAGE OF PUSH-PULL FATIGUE

系统地研究了［１１０］与［１００］两种特殊晶轴取向的高纯铝单晶在１×１０（－４）－６×１０（－４）室温拉压疲劳应变振幅条件下的应力σｍ、内耗Ｑ（－１）和加载最大处超声衰减△αｔ，的循环响应行为，对疲劳不同阶段的位错组态作了详细的ＴＥＭ观察。结果表明：两种单晶的循环应力均显示出“硬化－软化－二次硬化”的三个阶段特征。内耗的变化和应力进程同步，但趋势相反．超声衰减开始随圈数增大，达到一极大值后减小。这三种参数的变化是由位错与位错的相互作用机制控制。

Push-pull fatigue deformation of [110] and [100] Al-single crystals was performed at room temperature at strain amplitudes in the range (1 to 6) × 10￣(-4). Variation of the stress σ, internal friction Q￣(-1), and ultrasonic attenuation △α vs cycle number N under various strain amplitudes were measured systematically, and the relative dislocation configuration at different stages of fatigue was observed by TEM. The results indicate that the σ-N curve goes through a hardening -softening-secondary hardening sequence during push-pull fatigue in the two kinds of Al-single crystals. The change in the internal friction vs cycle N is synchronous and reverse with that of the stress. The ultrasonic attenuation △α increases with N at the beginning, after reaching a hump, decreases gradually. The variation of this three parameter is controled by the mechanism of interaction between dislocation segments.