A novel bypass-gas metal arc directed energy deposition for in-situ synthesis Al-Cu-Li alloy: exploring the microstructure and mechanical properties evolution from as-deposited state to T6 state

A novel bypass-gas metal arc directed energy deposition (bypass-GMA DED) was proposed to prepare high strength Al-Cu-Li-based components. An Al-5.51Cu-0.48Li alloy was successfully prepared, followed by subsequent T6 treatment. The microstructure evolution and improvement of mechanical properties after the T6 state were benchmarked against the as-deposited condition. The component fabricated by bypass-GMA DED has obvious periodic distribution characteristics, with a large number of fine equiaxed grains distributed near the interlayer fusion boundary and coarse columnar grains within the intralayer region. After heat treatment, the Al-5.51Cu-0.48Li alloy is mainly composed of four types of strengthening phases, θ’, θ”, δ’ and T1, which contrasts with the sole presence of θ phase in the deposited condition. These phases are conducive to the improvement of mechanical properties. The strength of the prepared alloy is higher than those additively manufactured Al-Cu-Li alloys, reaching values similar to those of conventional third generation Al-Cu-Li alloys.

一种创新的绕流气体金属电弧定向能量沉积技术（简称bypass-GMA DED）被提出，旨在制备高强度Al-Cu-Li基复合材料。成功制备了Al-5.51Cu-0.48Li合金，并随后进行了T6热处理。对T6状态下的微观结构演变及机械性能的提升与原沉积状态进行了基准对比。通过bypass-GMA DED技术制备的组件表现出明显的周期性分布特征，其中在层间熔合边界附近分布着大量细小的等轴晶粒，而在层内区域则存在粗大的柱状晶粒。经过热处理后，Al-5.51Cu-0.48Li合金主要由θ’，θ”，δ’和T1四种强化相组成，这与沉积条件下的单一θ相存在形成鲜明对比。这些相的存在有利于机械性能的提升。所制备合金的强度高于增材制造的Al-Cu-Li合金，其值接近传统第三代Al-Cu-Li合金的水平。