Thermal relaxation behavior of residual stress in peened dissimilar weld joints investigated by neutron diffraction

Akita, Koichi; Suzuki, Hiroshi  ; Nishikawa, Satoru*; Moriai, Atsushi; Harjo, S.   ; Vladimir, L.*

The materials used for the dissimilar weld joint were a SUS316L stainless steel and a NCF600 nickel alloy for the base plates, and an Alloy82 nickel alloy for the weld metal. The ultrasonic shot peening (USP) was applied to the sample surface after welding. The residual stress mappings of the as-peened and heat treated (593 K, 2 h) samples were measured at room temperature using KOWARI in ANSTO. In the results, the reduction of the tensile residual stress was observed near the interface of the weld metal and the nickel base plate. To clarify the relaxation process, the in-situ stress measurements during thermal cycles from RT to 593 K were conducted using TAKUMI in J-PARC. The effects of the difference in thermal expansion coefficient of the materials and the temperature dependence of the yield strength on the residual stress relaxation were disscussed based on the experimental results.