7A85铝合金位错密度模型与热变形过程中的微观组织研究

Dislocation density model and microstructure of 7A85 aluminum alloy during thermal deformation

通过金相观察和电子背散射衍射技术,研究了7A85铝合金在应变速率0.001~1 s^(−1)、变形温度250~450°C条件下的微观组织演变规律,并基于K-M位错密度模型,建立了7A85铝合金“两阶段”式K-M位错密度模型。结果表明,在7A85铝合金热变形过程中,动态回复和动态再结晶是微观组织演变的主要机制;350~400°C是动态回复向动态再结晶的转变温度区间。在低温条件(≤350°C)下主要发生动态回复,高温条件(≥400°C)主要发生动态再结晶;此时,微观组织演变对于温度的敏感性较高,且随着温度的升高,平均取向差角(θˉ_(c))显著增加,增加范围在0.93°~7.13°之间,同时微观组织中f_(LAGBs)明显减少,最高下降幅度达24%。

The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate(0.001−1 s^(−1))and deformation temperature(250−450°C)was studied by optical microscopy(OM)and electron back scattering diffraction(EBSD).Based on the K-M dislocation density model,a two-stage K-M dislocation density model of 7A85 aluminum alloy was established.The results reveal that dynamic recovery(DRV)and dynamic recrystallization(DRX)are the main mechanisms of microstructure evolution during thermal deformation of 7A85 aluminum alloy.350−400°C is the transformation zone from dynamic recovery to dynamic recrystallization.At low temperature(≤350°C),DRV is the main mechanism,while DRX mostly occurs at high temperature(≥400°C).At this point,the sensitivity of microstructure evolution to temperature is relatively high.As the temperature increased,the average misorientation angle(θˉ_(c))increased significantly,ranging from 0.93°to 7.13°.Meanwhile,the f_(LAGBs) decreased with the highest decrease of 24%.