This paper reveals the evolution of interfacial microstructure and its effect on the mechanical properties of Al alloy/stainless steel joint made by inertia friction welding with different surface roughness (as-machined and polished) followed by preheat treatment. At the central interface region, an unbonded area is witnessed for the Al alloy/as-machined steel (AA-MS) joint, while an intimate contact is realised for the Al alloy/polished steel (AA-PS) joint. The 1/2 radius (1/2R) region is characterised by the formation of the Fe–Al reaction layer, and no obvious layer exists at the peripheral region. Further microstructural characterisation indicates the reaction layer consists of a partially nanoscale crystallised layer of Fe₂Al₅ and a nanoscale amorphous layer in the as-welded joint induced by the severe shear effect. Preheat treatment promotes the growth of the crystallised layer and suppresses the amorphous layer due to the enhanced atom mobility. Preheat treatment improves the local interfacial bonding strength by reducing the unbounded area while maintaining a high bonding quality at the 1/2R region in the AA-MS joint. However, the enlarged brittle peripheral region is responsible for a slightly lowered joint strength in the preheated AA-PS joint.

本文揭示了界面组织的演变及其对不同表面粗糙度（如机加工和抛光）后热处理的惯性摩擦焊接铝合金/不锈钢接头力学性能的影响。在中心界面区域，铝合金/机加工钢 (AA-MS) 接头存在未粘合区域，而铝合金/抛光钢 (AA-PS) 接头则实现了紧密接触。1/2半径（1/2R）区域的特点是形成了Fe-Al反应层，外围区域不存在明显的层。进一步的微观结构表征表明反应层由部分纳米级的 Fe ₂ Al _{5结晶层组成}以及由严重剪切效应引起的焊接接头中的纳米级非晶层。由于增强的原子迁移率，预热处理促进了结晶层的生长并抑制了非晶层。预热处理通过减少无界区域来提高局部界面结合强度，同时在 AA-MS 接头的 1/2R 区域保持高结合质量。然而，扩大的脆性周边区域导致预热的 AA-PS 接头的接头强度略有降低。