Mechanical Properties and Parameter Optimization of TC4 Alloy by Additive Manufacturing

Additive manufacturing can realize die free, rapid and near net shape of complex structures with high densities. In order to ensure the forming quality of manufactured components, it is critical to establish a correlation mechanism between processing parameters, microstructure, and macro-mechanical properties in the additive manufacturing for metals. The Ti-6Al-4V alloy (referred to as TC4) is created by selective laser melting (SLM) using four distinct processing settings, and the microstructures are compared and discussed. The constitutive behavior is studied by uniaxial tensile tests under quasi-static conditions to determine the key mechanical properties such as flow stress and ultimate strain. The load-displacement curves of the TC4 alloy under the indentation strain rates of 0.01 / s and 0.10 / s are studied by nanoindentation experiments, in which the Young's modulus and hardness are obtained based on the continuous stiffness method. Finally, the effect of laser energy density during the SLM processing on the macro-mechanical properties of TC4 alloy is discussed by adopting the concepts of constraint factor and dislocation density, which combines the mechanical properties obtained from uniaxial tension and nanoindentation experiments. From a statistical standpoint, a correlation analysis is performed between SLM processing parameters and mechanical properties to elucidate the prevailing pathways among SLM processing parameters, microstructural morphology, and macro-mechanical properties. As a result, the most effective combination of processing parameters is identified and then used to tune the macro-mechanical properties of SLM-fabricated TC4 alloy. A guidance is provided for the SLM forming process parameters to improve the mechanical properties of TC4 material.