Influence of Grain Size on Microstructure and Mechanical Properties of Ti Alloy in TIG
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摘要: 进行了2μm及8μm,19μm三种晶粒尺寸的细晶粒TC4钛合金常规TIG焊试验,分析了母材晶粒尺寸对钛合金焊接接头组织转变规律及力学性能的影响.结果表明,细晶粒TC4钛合金焊缝中心和热影响区组织相似,为α马氏体组织.相同焊接规范下,随着晶粒尺寸的减小,焊缝中心和热影响区组织由编织(网篮)状α组织向片状组织过渡;随着晶粒尺寸的减小,热影响区晶粒长大越来越明显,热影响区细晶区(FHAZ)明显变窄,热影响区粗晶区(CHAZ)明显变宽,焊缝—热影响区—母材的晶粒梯度增大,焊接接头三区域晶粒过渡越来越差;随着晶粒尺寸的减小,焊接接头拉伸强度和伸长率均有不同程度的提高.常温拉伸断口呈准解理断裂特征,随着母材晶粒度的增大,焊接接头解理断裂特征越明显.Abstract: Fine grain TC4 alloy with various grain size(2μm,8μm,19μm)were welded by conventional TIG respectively,the microstructure and mechanical properties of welded joint were tested.The results show that the microstructure of weld center(WC)and heat-affected zone(HAZ)are α martensites.With the same parameters,and the reduction of grain size of base metal(BM),the microstructure of WC and HAZ change from lamellar α structures to basket α structures.With the reduction of grain size of BM,the grain growth tendency of HAZ become more apparent,the width of FHAZ is reduced,and the width of CHAZ is increased obviously,the crystal grain gradient of WC-HAZ-BM is increased,the grain transition of these three zones got worse,and the tensile strength and elongation were increased slightly.Tensile fractures of welded joint present character of quai-cleavage crack.Cleavage features of fractographs of weld joint are more obvious with increasing grain size of the base metal.
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Key words:
- grain size /
- TIG welding /
- microstructure /
- mechanical properties
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