3D激光沉积增材制造TC4高应变率动态力学行为及本构关系研究

通过对3D激光沉积TC4在较宽温度（298~1 073 K）和应变率范围（0.001~5 000 s^-1）内的单轴压缩试验，系统研究了该材料的塑性流动行为，分析了材料的微观组织特性及其变形断裂微观机制.结果表明材料在压缩载荷下具有明显的应变率硬化和温度软化效应.在压缩加载条件下，材料的破坏模式为绝热剪切带的萌生和拓展，而初始缺陷成为诱导剪切带形成的主要原因.3D激光沉积TC4材料屈服强度与铸造TC4接近，略低于传统锻造TC4.文中基于位错动力学热激活理论建立了可以较好描述材料在不同温度不同应变率下的塑性流动行为物理概念的本构模型.

Additive Manufactured Ti-6Al-4V Titanium Alloy Using 3D Laser Deposition: Dynamic Mechanical Behavior and Constitutive Relation

The uniaxial compressive and tensile tests were performed using an electronic universal testing machine and enhanced Hopkinson technique, over the range of strain rate from 0.001 s^-1 to 5 000 s^-1, and at temperatures from the room temperature to 1 073 K. Systematic study of the plastic flow behavior and the fracture microstructure characteristics of materials were accomplished. The effects of strain rate hardening and temperature softening can be reflected under compression loading. The formation and expansion of adiabatic shear bands are the primary fracture mechanism under compressive loading. Initial defects are the main reason to induce the formation of shear cracks. The comparison of the 3D laser deposition TC4 and traditional TC4 in mechanical properties shows that the material strength of the former is close to cast TC4 but slightly lower than that of traditional forged TC4 and the plastic performance is slightly superior. The plastic flow behavior of the additive manufactured Ti-6Al-4V can be well described by a physical constitutive model based on the dislocation dynamics and thermal activation mechanism.