Mechanical Properties of TIG Welding of ARAA Material

In this study, TIG welding and post weld heat treatment (PWHT) were conducted for 12-mm thick and 1350-mm long ARAA plates using the developed weld conditions and process to fabricate the test specimens for the mechanical property tests. To examine the TIG welding effect on the mechanical properties for ARAA, hardness tests, Charpy impact tests and tensile tests were applied to the heat affected zone (HAZ) and weld metal (WM) of the TIG welded joints after PWHT. ARAA is a main candidate of the structural material for Korean DEMO and fusion reactor, and its TIG welding technology would be applied to many joints for their construction, especially for the breeding blanket fabrication. Micro-Vickers hardness test and micro-structure analysis were conducted before and after PWHT to evaluate the effect of PWHT on the base metal and weld metal. Charpy Impact, tensile and bend tests were performed after PWHT. The micro-hardness results indicate that the profile of the hardness values for the materials after PWHT is more stable than before PWHT. The average hardness values before were 332 HV in the HAZ and 380 HV in the WM, and after PWHT, the values decreases to 250 HV in the HAZ and 258 HV in the WM. The maximum Charpy impact values in the HAZ and WM regions are 175 J at RT and 209 J at 0 .deg. C, respectively. The ductile brittle transition temperatures (DBTT) of all specimens were -50 .deg. C on the HAZ and -65 .deg. C on the WM. The DBTT of the weld metal was slightly less than the DBTT of HAZ, while the upper shelf energy (USE) was greater. The tensile test specimens were fabricated using dog-bone type specimens for room temperature, and cylindrical specimens for higher than room temperature. The tensile strength decreased as the temperature increased. The yield strength (YS) and ultimate tensile strength (UTS) were 542 MPa and 652 MPa, respectively.