TC4钛合金激光焊对接接头超塑变形显微组织

Microstrucutre analysis of superplastic deformation on laser butt weld Ti-6Al-4V joint

采用金相显微镜观察了钛合金激光对接接头超塑性变形前后各区域显微组织,并分析其形成机理.结果表明,变形温度的增加或应变速率的降低有利于TC4合金接头超塑变形,母材晶粒发生一定程度的长大,且α相的数量相对减小,而晶间β相数量逐渐增加,两相都有等轴化趋势;焊缝超塑性变形时,针状组织增厚成为片层状.变形过程中片层组织被打断,片层长度变短,具有球化的趋势;超塑性变形后焊缝截面显微硬度最大为380 HV,与变形前焊缝相比降低约50 HV,满足实际承载需求.

Microstructures of welded joints before and after superplastic deformation were observed by optical microscope,and the forming mechanism was discussed.The results indicated that increasing temperature and decreasing velocity were good for superplastic deformation,and the grains of base metal grew coarser and the phase ratio increased.Needle-like martensite phase of weld bead became shorter and wider,exhibiting globing trend under higher temperature.The maximal microhardness of cross section of weld bead after deformation is 380 HV,about 50 HV lower compares with original weld bead,which meets the requirnement of the actucal lead.