Mechanical properties of base metal and heat-affected zone in friction-stir-welded AA6061-T6 at ultra-low temperature of 20 K

AA6061-T6摩擦攪拌接合における母材および熱影響部の20K超低温での機械的性質

Nguyen, T.-D.*; Singh, C.*; Kim, Y. S.*; Han, J. H. *; Lee, D.-H.*; Lee, K.*; Harjo, S.   ; Lee, S. Y.*

Nguyen, T.-D.*; Singh, C.*; Kim, Y. S.*; Han, J. H. *; Lee, D.-H.*; Lee, K.*; Harjo, S.; Lee, S. Y.*

This study investigates the mechanical properties of a friction-stir-welded (FSW) AA6061-T6 aluminum alloy at ultra-low temperature (ULT) of 20 K. In-situ neutron diffraction and orientation imaging microscopy were employed to compare the tensile deformation behavior of the base metal (BM) and heat-affected zone (HAZ) in the FSW aluminum plate. The results demonstrate that compared to room-temperature (RT), ULT induces a significant improvement in tensile strength and ductility in both the BM and HAZ. The enhanced mechanical properties in BM at ULT result from a more homogeneous deformation than occurs at RT. On the other hand, HAZ at ULT exhibits an even lower yield strength than at RT, but the strain hardening rate (SHR) is the most significant among the alloys, leading to a tensile strength of 346 MPa and the highest ductility of 46.8%. The lowest yield strength corresponds to the lowest-hardness zones in HAZ, caused by dissolved/coarsened precipitates during the FSW process.