铝合金/合金钢异种金属摩擦焊接头组织与性能

Microstructure and properties of friction welded joint of aluminum alloy to alloy steel

针对油气资源勘探开发用钻杆轻量化的需求,以小尺寸试棒7075-T6铝合金和37CrMnMo合金钢利用连续驱动摩擦焊技术实现连接,探索开发铝合金/合金钢轻量化复合钻杆焊接制造的可能性和可行性,研究了焊接工艺参数对接头成形、微观组织及力学性能的影响.结果表明,接头界面铝侧的晶粒受到力和热的作用发生完全动态再结晶,而在热力影响区发生了不完全动态再结晶.界面沿径向热力分布的不均匀导致了在中心区域没有化合物产生,但在1/2半径区域有亚微米级的化合物层生成,接头抗拉强度最大可达240 MPa.中心区域较为平整的断裂面说明该区域是接头的薄弱环节.因此仍需进一步调控铝合金/合金钢摩擦焊接过程,促进中心区域冶金结合,以提升接头整体强度.

On account of the urgent demand of lightweight drilling pipe,a composite structure made by 7075-T6 aluminum alloy and 37CrMnMo alloy steel was welded by continuous-drive friction welding method so as to offer the optimized manufacturing process and theoretical support for manufacturing lightweight Al/steel composite drilling pipe.The effects of welding parameters on the appearance,microstructure and mechanical properties of the joint were investigated.The results indicated that the fine grain zone with texture<111>in radius direction appeared at the weld interface due to the fully dynamic recrystallization in the Al side under sufficient heat and pressure,which results in the grainboundary strengthening under the coupling effect of force and heat.In the heat affected zone,the original fiber texture<111>and<110>in the base metal disappeared with random orientations appeared as a result.The inhomogeneous distribution of heat and force along the radius direction led to intermetallic compounds(IMCs)free zone existing at central zone of weld interface,while a sub-micron sized IMCs layer formed at 1/2 radius zone.Following by the dissolution of second phase particles,the micro-hardness along longitudinal section tended to reach a dynamic equilibrium trend after experiencing a reduction and ascending process at weld interface.The bonding mechanism was in a combined form of mechanical and metallurgical joining,with the highest strength achieved 240 MPa.The relatively smooth fracture appearance at central zone manifested itself a weaker bonding,which revealed that a metallurgical reaction at such zone is highly desired by controlling the friction process in order to further enhance the joint property.