Investigation of the Effect of Nickel Interlayer on the Microstructure an‎d Mechanical Properties of Dissimilar Joint between 316L Stainless Steel an‎d Pure Copper Using Friction Stir Welding

10/14/2025 12:00:00 AM

In this study, the effect of a nickel powder interlayer on the microstructure an‎d mechanical properties of a dissimilar joint between 316L stainless steel an‎d pure copper was investigated using the friction stir welding (FSW) process. For comparison, five samples were prepared, including welds with an‎d without the nickel powder interlayer. Among these, defects were observed in samples A3, A4, an‎d A5, while samples A1 (with Ni interlayer) an‎d A2 (without interlayer) were selec‎ted as the optimal conditions, using a rotational speed of 1140 rpm, a traverse speed of 44 mm/min, an‎d an interlayer thickness of 0.3 mm. Microhardness an‎d uniaxial tensile tests were conducted for all samples, an‎d the results were compared. Microstructural analyses revealed that in sample A2 (without the Ni interlayer), material transfer from the steel side to the copper side led to the formation of small steel fragments within the weld zone, whereas this phenomenon was not observed in sample A1 due to the presence of the nickel interlayer. The addition of nickel in sample A1 significantly increased the hardness in the steel-side stir zone, which consequently induced stress concentration an‎d caused fracture to occur in the copper-side stir zone. In contrast, in sample A2, the absence of an interlayer an‎d the tool offset toward the copper side resulted in higher heat accumulation in this region, leading to more severe grain coarsening an‎d a weaker heat-affected zone (HAZ), where fracture eventually took place.From a mechanical stan‎dpoint, the ultimate tensile strength (UTS) of samples A1 an‎d A2 was measured to be approximately 190 MPa an‎d 165 MPa, respectively, while their elongation percentages were around 6% an‎d 10%. Fractography revealed a mixed brittle–ductile fracture in the weld region of sample A1 an‎d a ductile fracture in the HAZ of sample A2, which is consistent with the tensile test results.

جوشكاري اصطكاكي همزدني , لايه مياني پودر نيكل , جوشكاري غير هم جنس , فولاد زنگ نزن , مس خالص

Friction stir welding , , nickel powder interlayer , , dissimilar welding, , stainless steel L 316 , , pure copper

Abbas Ghenaatkar

Dr. Hamidreza Koohdar