高温瞬时和热暴露对2024铝合金组织与性能的影响

THE INFLUENCES OF SHORT-AND LONG-EXPOSED TIME AT ELEVATED TEMPERATURES ON THE PROPERTIES AND MICROSTRUCTURES OF ALUMINIUM ALLOY 2024

本文利用透射电镜研究了高温瞬时和热暴露对2024 T3511状态铝合金拉伸性能的影响及对应的组织变化。实验结果说明,经高温瞬时和热暴露后,强度曲线经过一段平缓阶段迅速下降;而塑性曲线一反常态,塑性与温度不呈单调函数关系,曲线中间有一最低值。微观分析表明,合金存在两种类型时效沉淀相S系列相和X相。S系列相(G.P.区形核)遵循以下时效序列: G.P.区—→S″—→S″+S′—→S′+S—→SX相在S″+S′阶段内析出。与强度曲线平缓阶段对应的组织是G.P.区和S″相,与强度开始下降阶段和塑性最低区域对应的组织为S′+S″+X,这与半共格S′和X的形成有关。与强度下降和塑性回升阶段对应的时效组织是非共格S+X相。

The influences of short-and long-exposed time at elevated temperatures on tensile properties and microstructures in 2024 T3511 condition have been studied by TEM. The experimental results show that after heat-treatments, the strength curves have passed through a smooth stage and dropped rapidly: the relationship of plasticity and temperature is not a monotonous ruction, there is a lowest plastic value in the middle of curve. The microstructure analysis indicates that there are two types of aging phases: S sequence (forming in G.P.area) and X phase (forming in high temperature), the S aging sequences are as follows: G.P.area→S″→S″+S′→S′+S→S and the X phase forms during precipation of S″+S. The microstructures corresponding to smooth stage of the strength curve are G.P.area and S″ phases, and the microstructures, corresponding to the begining drop stage of strength curve and the lowest area of plasticity are S′+S″+X, which is related to semi-coherent S′ and X. The drop stage of strengh and the increase stage of plasticity are in relationship with non-coherent S+X Phases in ageing structure.