界面约束作用下Ti/Al多层复合材料的力学性能和冲压成形性能

Mechanical Performance and Stamping Formability of Ti/Al Multilayer Composites Under Interface Constraint Effect

摘要:

采用热压+热轧复合法在500 ℃制备了3层、5层和7层配置的Ti/Al多层复合材料（LMCs），研究了拉伸和埃里克森杯突试验过程中复合板的裂纹萌生和扩展行为，分析了界面约束效应对复合板力学性能和冲压成形性能的影响机理。结果表明，复合板界面具有微米级厚度的金属间相，导致其具有较强的界面结合。随复合板层数的增加，其屈服强度（YS）和极限抗拉强度（UTS）增加，延伸率（EL）和韧性降低，且由于热轧形成了强基面织构，复合板力学性能的各向异性明显增加。同时，复合板的加工硬化指数（n）和塑性应变比（r）均降低，屈强比（σ_s/σ_b）增大，这些均导致了复合板的冲压成形性能变差。对于层数较少的复合板，在断裂过程中界面脱粘起了主要作用。由于界面结合不佳，界面易发生分层，通过抑制裂纹萌生、促进裂纹偏转和钝化、降低裂纹扩展的驱动力，有效地延缓了复合板的断裂失效。

Abstract:

Ti/Al layered metal composites (LMCs) with 3, 5 and 7 layers were prepared via hot-pressing followed by hot-rolling at 500 °C. The crack initiation and growth behavior in LMCs during tensile and Erichsen cupping tests were explored. The influence mechanism of interface constraint on the mechanical performance and stamping formability of LMCs was analyzed. Results show that LMCs exhibit strong interfacial bonding due to intermetallic phase with micron-scale thickness. As the layers of LMCs increase, their yield strength (YS) and ultimate tensile strength (UTS) increase accompanied with the reduction in the elongation (EL) and toughness, and their anisotropy of mechanical performance increases obviously due to the strong basal texture formed by hot-rolling. Meanwhile, both the work-hardening exponent (n) and plastic strain ratio (r) decrease, but the yield strength ratio (σ_s/σ_b) increases, which deteriorates the stamping formability of LMCs. Interfacial delamination plays a crucial role in the fracture for LMCs with fewer layers. The interface is prone to delamination because of poor interfacial bonding, which delays the fracture failure of LMCs by inhibiting crack initiation, promoting crack deflection and passivation, and reducing the driving force of crack propagation.