铅-钙-锡-铝合金固溶后时效过程中的不连续脱溶与再结晶行为

Discontinuous Precipitation and Recrystallization Behavior of Pb-Ca-Sn-Al Alloy during Aged Process after Solid-Solution Treatment

采用光学显微镜、场发射扫描电镜、EDS能谱仪和显微硬度计等研究了Pb-0.05%Ca-1.5%Sn-0.026%Al(质量分数)合金经不同工艺固溶后在100℃时效过程的不连续脱溶与再结晶行为。结果表明:该合金经不同工艺固溶后晶粒尺寸均约为1 000μm;经270℃保温30 min后空冷+310℃保温30 min水冷固溶(A工艺)再时效35 h后的晶粒细化至300～400μm,经270℃保温30 min水冷(B工艺)再时效12 h后的晶粒细化至60μm;由于不连续脱溶组织形核、生长使原有晶粒细化,实现了不借助塑性变形的再结晶;在不同固溶工艺下,合金时效时发生不连续脱溶所需保温时间及晶粒细化的程度也不同;随保温时间延长,A工艺处理合金的硬度曲线出现两处峰值,二次硬化相均为(PbSn)3Ca,B工艺处理合金的硬度曲线无规律可循,且细晶组织不稳定。

The discontinuous precipitation（DP） and recrystallization behavior of the Pb-0.05%Ca-1.5%Sn-0.026%Al（mass fraction） alloy during aged at 100 ℃ after solid-solution by different processes were analyzed by means of optical microscope,scanning electron microscope,X-ray energy dispersion spectroscope and micro hardness tester.The results show that all the grain size of the alloy after solid-solution by different processes was about 1 000 μm.After aged at 100 ℃,the grain size of the alloy aged for 35 h was refined to 300-400 μm after solid-solution at 270 ℃ for 30 min cooled in air and heated at 310 ℃ for 30 min cooled in water（process A）,while the grain size of the alloy aged for 12 h was refined to 60 μm after solid-solution at 270 ℃ for 30 min cooled in water（process B）.The grain refinement was due to the nucleation and growth of DP,and the recrystallization could be achieved without plasticity deformation.The holding time for the discontinuous precipitation during aged process of the alloy and the grain refinement were different with various solid-solution processes.With the prolongation of the holding time,there were two peak values on the hardness curves of the alloy treated by process A,the secondary hardening phase was（PbSn）3Ca.The hardness curves of the process B had no rule to follow,and the fine-grained microstructure was unstable.