The automotive and aerospace industries increasingly rely on lightweight, high-strength materials to improvefuele൶ciency,makingthejoiningofdissimilarmetalssuchasaluminumandsteelbothbene¿cialandessential.However,amajorchallengeinthesejointsistheformationofbrittleintermetallic compounds (IMCs) at the interface, even when using low heat-input solid-state welding methods likefrictionstirwelding(FSW).Furthermore,IMCgrowthatelevatedtemperaturessigni¿cantly limits the service life of these joints. In this study, an intermediate layer of stainless steel was deposited on the steel surface prior to FSW with aluminum. The resulting Al–Steel joints were subjected to heat treatment at 400 °C and 550 °C to investigate IMC growth and its impact on mechanical strength, with results compared to conventional joints without the intermediate layer. The intermediate layer signi¿cantlysuppressedIMCformation,leadingtoasmallerreductioninmechanicalstrengthafter heat treatment. Joints with the intermediate layer achieved their highest strength (350 MPa) after heat treatment at 400 °C, while conventional joints exhibited their highest strength (225 MPa) in theas-weldedcondition.At550°C,bothjointtypesexperiencedadeclineinstrength;however, the joint with the intermediate layer retained a strength of 100 MPa, whereas the conventional joint lost its strength entirely. This study provides an in-depth analysis of the role of IMC growth in joint strength and demonstrates how the intermediate layer enhances the thermal durability and mechanical performanceofAl–Steeljoints,oeringvaluableinsightsfortheirapplicationinhigh-temperature environments.
