Texture evolution and properties analysis of R60702 pure zirconium joint by fiber laser welding

Abstract

Fiber laser welding of R60702 pure Zr was performed in this study. The joint was composed of base metal (BM), fine grain heat affected zone (FGHAZ), coarsened grain heat affected zone (CGHAZ) and weld zone (WZ), which was fractured at BM during tensile testing. WZ presented the highest hardness 240 HV1, while the lowest hardness 160 HV1 detected at BM. The microstructure in the WZ was composed of basket-weave Widmanstatten structures, and parallel-plate α' structure. The microstructure in the HAZ was composed of parallel-plate α' structure, a small amount of basket-weave Widmanstatten structure and irregular shape α' recrystallized grains. The proportion of grain sizes (≤12 μm) in BM, FGHAZ, CGHAZ and WZ were 67.9%, 86.4%, 83.1% and 90.6%, respectively. Texture evolution was characterized by electron backscatter diffraction (EBSD) and XRD. XRD results indicate that the joint was composed of α-Zr, and demonstrated a different crystal texture in WZ and HAZ compared with BM. The typical bimodal texture appeared in BM. The possible existence of textures 101¯0<12¯10> and 011¯3<2¯110> in BM. There are 101¯0<12¯10>, 011¯2<21¯1¯0>, 2¯110<0001> texture appeared in FGHAZ, and 101¯0<12¯10>, 011¯3<2¯110>, 1¯21¯0<202¯3> texture appeared in CGHAZ. In addition, 1¯21¯0<202¯3> and 011¯3<2¯110> texture appeared in WZ.