Effect of welding heat input on microstructure and properties of TC4 titanium alloy ultra-narrow gap welded joint by laser welding with filler wire

Abstract

A 10 mm narrow gap TC4 titanium alloy welded joint by laser welding with filler wire was obtained by different welding heat inputs. The microstructures of the welded joint were analyzed by OM, SEM, XRD and EBSD. The mechanical properties of the welded joint were analyzed by microhardness test and tensile test. The results show that with the increase of laser welding heat input, the average grain size and width of the equiaxed crystal zone in the center of the weld increases, the grain angle in the columnar crystal zone gradually tends to be perpendicular to the center of the weld, and the width of the heat affected zone (HAZ) increases without obvious grain coarsening. The HAZ of the welded joint is softened, and its microhardness value is lower than that of the weld and the base metal. The tensile strength of the welded joint is slightly higher than those of the base metal, but the elongation after fracture is less than that of the base metal, and it decreases with the increase of laser welding heat input.

Research on Parameters of Wire-Filling Laser Welding and Quenching Process for Joints Microstructure and Mechanical Property of BR1500HS Steel

“…When the welding speed increases, the effect of heat on the weld per unit length is less, reducing the melting volume of the welding wire and BM. Then the temperature of weld is lowered, and the width of the weld and heat affected zone is narrowed [18][19].…”

“…It can be found that BM had more orientation of blue {111} and red {001} generated by the quenching process. The whole joint is identified in random orientation after quenching [19][20]. The grain boundary misorientation and statistical results of the joint before and after quenching is showed in Fig.…”

“…A large number of dimples and section of river patterns can be observed on the fracture morphology. So, the ductile fracture indicates that the weld joint before quenching has a good plasticity [19]. However, some river patterns and many voids are also observed in the dimples, mainly due to the high martensite strength and poor ductility after quenching, and a large number of secondary cracks and dissociation platform occur during the tensile process [21].…”

Research on Parameters of Wire-Filling Laser Welding and Quenching Process for Joints Microstructure and Mechanical Property of BR1500HS Steel

“…For welded joints, defects such as underfill, crack, and weld porosity have serious effects on the weld appearance and joint mechanical properties. Therefore, the weld joint should not contain underfill defects, cracks, and weld porosities [17][18][19]. Furthermore, the shape of the joint cross-section requires a flat or convex face.…”

“…It can be found that the BM has more orientations of blue {111} and red {001} generated by the quenching process. The whole joint is identified in random orientation after quenching [19,20].…”