7B04铝合金超塑性变形行为

针对7B04铝合金开展了变形温度为470~530℃,应变速率为0.0003~0.01s~(-1)的高温超塑性拉伸实验,研究了材料的超塑性变形行为和变形机制。结果表明,7B04铝合金的流动应力随着变形温度的升高和应变速率的降低而逐渐减小,伸长率随之增加;在变形温度为530℃,应变速率为0.0003s~(-1)时,7B04铝合金的伸长率达到最大1105%,超塑性能最佳;应变速率敏感性指数m值均大于0.3,且随变形温度的升高而增加;在500~530℃的变形温度范围内,m值大于0.5,表明7B04铝合金超塑性变形以晶界滑动为主要变形机制;变形激活能Q为190kJ/mol,表明7B04铝合金的超塑性变形主要受晶内扩散控制;7B04铝合金超塑性变形中在晶界附近有液相产生,且适量的液相有利于提高材料的超塑性能。

Superplastic Deformation Behavior of 7B04 Al Alloy

The superplastic tensile tests were carried out for 7B04 Al alloy under a temperature range of 470-530℃ at a strain rate range of 0.0003-0.01s-1.Then,the superplastic deformation behavior and deformation mechanism of the material were investigated.The results show that with the increase of temperature and decrease of strain rate, the flow stress of 7B04 Al alloy is decreased and the elongation is increased.When the deformation temperature is at 530℃ and the strain rate is 0.0003s-1, the elongation reaches the maximum value of 1105%, which indicates that at this process parameter the optimal superplasticity is obtained;the strain rate sensitivity index m value is above 0.3 and increases as the temperature going up;when the deformation temperature is at the range of 500-530℃, the m value is above 0.5,the superplastic deformation mechanism of 7B04 Al alloy predominated by grain boundary sliding;the superplastic deformation activation energy Q value is 190kJ/mol which indicates that the superplastic deformation is significantly controlled by the intercrystalline diffusion;the liquid phase will be produced along the grain boundaries of 7B04 Al alloy during superplastic deformation,which can enhance the superplasticity with a moderate amount.