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

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.