高性能轻合金搅拌摩擦增材制造成形机理及组织控制

Focusing on the currently advanced friction stir additive manufacturing(FSAM) of aluminum and magnesium light alloys with high properties, we investigate the application fundamental issues of forming mechanism, microstructure control and mechanical properties during the friction stir additive manufacturing which are included as follows. The forming theory fundamentals and specific processing principles of friction stir additive manufacturing; the varying laws of friction thermal-mechanical coupling features and additive thermal cycles during friction stir additive manufacturing; the interactive and influencing rules between the processing parameters and heat inputs, strains and strain rates with the additive manufacturing processes; the interactive and influencing rules between the additive base material compositions, geometries and heat treatment conditions with the additive manufacturing processes; the forming mechanism of welding defects, the evolution of microstructures and the control rules and representations of inhomogeneous microstructures in the additive welds and layer interface zones; the evolution rules of fatigue strength and fracture toughness in the additive welds and layer interface zones; the susceptibility to defects, fracture modes and failure mechanisms in the additive welds and layer interface zones; the effects of inherent factors and mechanisms on the fatigue and fracture performances of additive weld regions; the material metallurgical and processing methods to control and improve the performances of friction stir additive manufacturing welds. The research results include the fundamental theory of friction stir additive manufacturing, the principle of processing and the specific devices, the varying rules of mechanical properties and microstructure control, which should provide the important foundation of developing the industrial application of friction stir additive manufacturing technology.

针对高性能铝镁轻质合金的搅拌摩擦增材制造工艺过程：研究搅拌摩擦增材成形机理、组织控制及力学性能的应用基础问题。具体包括搅拌摩擦增材成形理论基础及工艺原理；搅拌摩擦增材过程中热-力耦合特征及增材热循环变化规律；各种工艺参数及热输入、应变及应变速率与增材成形的相互影响机制；增材母材组织成分、尺寸形状及热处理状态与增材成形的相互作用规律，增材焊缝区及界面的焊接缺陷形成机制、组织演变及非均质组织表征与控制规律；增材焊缝区与界面的断裂韧度及疲劳强度演变规律，增材焊缝区及界面缺陷敏感性、断裂模式及失效机制、影响增材焊缝区断裂韧度和疲劳强度的内在因素及机制、控制与改善搅拌摩擦增材焊缝综合性能的材料冶金和工艺措施。研究结果包括搅拌摩擦增材成形基础理论、工艺原理及实现装置、组织控制及力学性能变化规律，为实现工业化搅拌摩擦增材制造技术的开发与应用提供重要基础。

针对高性能铝及镁轻质合金的搅拌摩擦增材制造(Friction Stir Additive Manufacturing, FSAM)工艺过程：研究搅拌摩擦增材成形机制、增材微观组织调控及力学性能的应用基础问题。具体包括搅拌摩擦增材制造成形理论基础及工艺原理；搅拌摩擦增材过程中热-力耦合特征及增材过程中热循环变化规律；各种工艺参数及热输入、应变及应变速率与增材成形的相互影响机制；增材母材组织成分、尺寸形状及热处理状态与增材成形的相互作用规律，增材焊缝区及连接界面的冶金缺陷形成机制、组织演变及非均质组织表征与控制规律；增材焊缝区与连接界面的断裂韧度及疲劳强度演变规律，增材焊缝区及连接界面缺陷敏感性、断裂模式及失效机制、影响增材焊缝区断裂韧度和疲劳强度的内在因素及机制、控制与改善搅拌摩擦增材综合性能的材料冶金和工艺措施。..通过项目研究建立了进行搅拌摩擦增材制造(FSAM)的试验平台、增材工艺参数压力测试平台及实现单道多层增材的试验夹具，对搅拌摩擦增材成形过程、搅拌摩擦工具及增材工艺窗口范围进行大量工艺试验，获得大量铝合金搅拌摩擦增材中增材流动特征、组织及界面结合特征、增材分层力学性能的原始数据；证实FSAM具有完全致密细化组织特征及良好的综合性能；FSAM增材界面前进侧具有良好的材料混合特征、但后退侧容易产生弱连接缺陷，导致增材及界面区具有明显组织及力学性能不对称性；增材界面处表面氧化物分散不均匀是影响其断裂及疲劳强度的关键因素；FSAM工艺过程繁琐每道增材板条都需要刚性固定及表面打磨处理，在工业化应用中具有局限性。对实现填充材料的摩擦挤压增材制造(Friction extrusion additive manufacturing, FEAM)工艺原理及装备进行大量的研究，独立设计研制了实现填充材料的FEAM用主轴头机构，在国内首次证实填充材料的摩擦挤压增材制造工艺的有效性及可行性，与FSAM增材工艺比较实现填充材料的摩擦挤压增材制造工艺具有明显的优势。目前已建立了摩擦挤压增材制造试验平台，为进行增材工艺试验、增材组织及性能评估、工业化固相摩擦挤压增材制造装备开发与应用提供重要基础。