易拉罐用铝材的锯齿屈服现象

Serration flow phenomenon of aluminum alloy used for can body stock

在应变速率为5.56×10-5～5.56×10-3s-1的范围内,从223～773K,每间隔25K的温度下对易拉罐用铝材进行系列拉伸实验,探索其锯齿屈服规律。结果表明易拉罐用铝材在形变过程中会出现动态应变时效现象;在给定的应变速率下,动态应变时效仅发生在一定的温区;在该温区内,应变速率敏感性出现了负值,强度出现了一个平台;并存在临界应变量转折温度Tt,在温度低于Tt的温区,动态应变时效是由于Mg溶质原子气团与位错交互作用的结果;在温度高于Tt的温区,存在两个相反的热激活过程,一是溶质原子运动至位错并钉扎位错;另一个过程是吸收源吸收溶质原子减弱对位错的钉扎作用。

An aluminum alloy used for can body stock was subjected to tension test at a strain rates range of 5.56×10~5 to 5.56×10~3 s^1 and temperature between 223 to 773K to investigate the effects of temperature and strain rate on its mechanical properties. The serration flow phenomenon is associated with dynamic strain aging (DSA) and yield a negative strain-rate dependence of the flow stress. In the serrated yielding temperature region a critical transition temperature (T_t) exists. The critical plastic strain for the onset of serrations has a negative or positive temperature coefficient within the temperature region lower or higher than T_t. According to the activation energy, it is believed that the process at the temperature region lower than T_t is caused by the interaction between Mg solute atom atmosphere and dislocation. In the positive coefficient region two reverse thermal activation processes occur simultaneously. One is the solute atoms diffuse to the moving dislocation and pin the dislocation. The other one is the absorbed resource absorbs the solute and diminishes the pinning effect.