Shui-liang ZHOU’s research while affiliated with Beijing Institute of Aeronautical Materials and other places

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.