Csf/Mg复合材料近基体固相线塑性变形力学、组织演变行为及挤压成形机理研究

Considering reinforcement breaking, interface debonding and nonuniform of microstructure in plastic processing of discontinuous reinforced magnesium alloy composites, a novel plastic processing technic, which fabricate magnesium based composite parts by extrusion near the solidus of matrix is proposed. The deformation behavior of Csf/Mg composite at temperature near the solidus will be investigated in order to reveal the interaction and adaption mechanism between the fiber redistribution，matrix plastic deformation and interface sliding. To construct the plastic mechanics constitutive and microstructure evolution model, the effect of deformation parameters on flow stress and microstructure characteristic is evaluated. The evolution of fiber and interface structure depending on thermal and mechanical distribution will be further reseached so as to reveal the relationship between forming ability and deformation conditions. Based on these investigations, the influence of extrusion parameters on microstructure, fiber orientation and interfacial structure in composite parts extruded near the solidus of matrix are investigated and the forming principle as well as toughening mechanism of extrusion processing will be clarified. The research will provide a sound basis for manufacturing high performance short fibers reinforced magnesium composite parts.

针对非连续增强镁基复合材料塑性加工中增强相/基体变形不协调引起的成形困难及组织结构缺陷难以控制的瓶颈问题，本项目提出短碳纤维增强镁基复合材料近基体固相线塑性成形新方法，利用基体较强的动态再结晶能力和非连续微量界面液相增强其塑性成形能力，避免纤维断裂、界面脱粘及组织成分偏析等成形缺陷，满足高性能复合材料构件塑性加工需求；研究复合材料近基体固相线塑性变形力学行为、基体组织与纤维取向分布演变规律，探讨基体微观塑性流动与纤维偏转行为的相互作用机理及其界面运动协调机制，建立复合材料塑性变形力学本构关系和微观组织结构演变模型；研究近基体固相线塑性变形参数对纤维结构损伤和界面结构缺陷特征的影响规律，建立复合材料塑性成形极限条件；在此基础上，分析近基体固相线挤压工艺参数对微观组织结构特征的影响规律，探明其与制件力学性能的内在关系，揭示复合材料近基体固相线挤压成形机理，为镁基复合材料构件的可控制备奠定基础。

非连续增强镁基复合材料相比镁合金具有比强度和比模量高、热膨胀系数低和耐磨减震性能好的特性，相比连续纤维增强镁基复合材料又具有各向同性性能好和制备成本低的优势，是航空航天和交通领域极具竞争力的金属基复合材料。目前镁基复合材料均需二次挤压或轧制加工以改善其制备态微观组织和性能。针对镁基复合材料塑性变形能力差和成形困难的难题，本研究提出了非连续增强镁基复合材料近基体固相线高温塑性成形技术。以真空压力浸渗法制备的Csf/AZ91D镁基复合材料为对象，系统研究了塑性变形温度和应变速率等参数对其流变力学行为和显微组织演化行为的影响规律，通过与镁合金高温塑形变形行为的对比研究，揭示了短纤维参与下的镁基复合材料独特的高温塑性变形机理，建立了其高温塑性流变力学本构方程和动态再结晶组织演变模型，开发了镁基复合材料塑性成形过程中传热-变形-组织演变多场耦合的有限元建模和数值模拟方法，为实现短纤维增强镁基复合材料高温塑性成形及其微观组织与性能控制奠定了基础。本研究提出并发展的非连续增强镁基复合材料近基体固相线高温塑性成形技术和理论，不但丰富了非连续增强金属基复合材料塑性加工理论体系，而且在难变形金属基复合材料塑性加工领域具有较大的应用潜力，对于推动非连续增强金属基复合材料的加工和应用发展具有重要的意义。