Microstructure and anisotropic mechanical properties of selective laser melted Ti6Al4V alloy under different scanning strategies

Apparent anisotropies have been found in the microstructure and mechanical properties of selective laser melted (SLM) Ti-6Al-4V alloy, which will significantly influence the comprehensive performance of the SLM parts. In this study, the effect of scanning strategies on material anisotropy, including surface morphology, microstructure, microhardness, quasi-static and dynamic mechanical properties, were comprehensively investigated with 0 degrees, 67.5 degrees, and 90 degrees scanning strategies. The SLM Ti6Al4V alloy prepared by the 0 degrees scanning strategy exhibited the most pronounced anisotropy. The size of the primary columnar crystals on the front surface (158-173 mu m) is approximately 1.8-3.2 times larger than that of the top surface (54-88 mu m), and the microhardness at the top surface is similar to 30% higher than that of the front surface. In addition, the modified Johnson-Cook constitutive model for the SLM Ti6Al4V alloy is developed based on the results of quasi-static compression and dynamic compression with the average absolute relative error controlled within 10%. This provides a reliable solution and an effective material constitutive model for modelling and simulation of the machining SLM parts with higher accuracy and enhanced physical meaning.

Automated summary

Anisotropies have been found in the microstructure and mechanical properties of SLM Ti-6Al-4V alloy, with the most pronounced anisotropy observed in the 0 degrees scanning strategy. The size of primary columnar crystals on the front surface is significantly larger than that on the top surface, with a microhardness difference of approximately 30%. A modified Johnson-Cook constitutive model for the SLM Ti6Al4V alloy has been developed with good accuracy for modeling and simulation purposes.