铸态Al-Zn-Mg-Cu铝合金多道次压缩变形行为及组织演变

Deformation behavior and microstructure evolution of as-cast Al-Zn-Mg-Cu aluminium alloy subjected to multi-pass compression

利用Gleeble-3500热力模拟试验机研究了铸态Al-Zn-Mg-Cu铝合金单道次等温和多道次非等温压缩变形行为,分析了其流变应力和组织演变规律。结果表明,随着变形道次增加和道次变形温度降低,流变应力值增大,不同道次间歇内应力软化程度变化不明显,原始晶粒压缩至长宽比约4∶1时晶粒在有利位向开始细化,累积真应变为0. 9时原始长条状晶粒破碎成细小等轴晶;随着热压缩后保温时间增加,组织发生回复,晶粒短轴变宽,两道次压缩组织演变为原始晶粒长宽比减小,三角晶界处的破碎小晶粒在保温30 s过程中向原始晶粒扩展长大,第二相逐渐溶解;三道次压缩及其在保温30 s过程中组织演变为原始晶粒长宽比减小,原始晶粒细化和新晶粒长大,第二相在热压缩过程中回溶,并在保温时析出。

The deformation behaviors of as-cast Al-Zn-Mg-Cu aluminium alloy in single-pass isothermal and multi-pass non-isothermal compression were studied using Gleeble-3500 thermal simulator. The rules of flow stress and microstructure evolution were analyzed. The results show that the flow stress increases with the increase of passes and the decrease of temperature,and the stress softening is not evident in inter-pass holding interval. The length-width ratio of 4∶ 1 in grain is benificial to grain refinement. The elongated grains are broken to refined and equiaxial grains with the accumulated true strain of 0. 9. As the holding time after compression increases,the recovery occurs and the short axis of grain becomes wider. The microstructure evolution in two-pass is characterized by the decrease of length-width ratio,the broken small grains in triangle grain boundaries grow up extend to original grains in the holding time of 30 s,and the second phases are dissolved in holding time. The microstructure evolutions in three-pass and subsequent holding time of 30 s are characterized by the decrease of length-width ratio,the initial grains are refined and new grains grow up. The second phases are dissolved during the compression process and precipitated in holding time.