Stress–strain behavior of a selective laser melted Ti-6Al-4V at strain rates of 0.001–1/s and temperatures 20–1000 °C

Abstract

Abstract Because of the lack of systematic studies of high-temperature mechanical properties of Ti-6Al-4 V fabricated using selective laser melting (SLM), the measurement of mechanical properties of SLMed Ti-6Al-4 V under thermomechanical conditions during SLM processing is necessary for accurate thermomechanical analyses of SLM processes. This study conducted compression tests of Ti-6Al-4 V fabricated by SLM and newly obtained stress–strain curves under thermomechanical conditions that are typical of those experienced during SLM processing (20–1000 °C temperatures and 0.001–1 /s strain-rates). This study also revealed that correlation between the maximum flow stress of SLMed Ti-6Al-4 V, the strain rate, and the temperature, respectively, with the Zener–Hollomon parameter (Z parameter) at temperatures of 600–1000 °C and strain rates of 0.001–1/s. A comparative study revealed that 0.2 % offset yield stress at temperatures 20–1000 °C had up to 43 % difference between the SLM-processed and conventional wrought Ti-6Al-4 V. This result indicates that not the mechanical properties of the wrought Ti-6Al-4 V but those of SLMed Ti-6Al-4 V should be used for conducting accurate thermomechanical analysis of SLM processing of Ti-6Al-4 V. Based on the obtained results, this study developed a constitutive equation using the Z parameter. It enabled calculation of the maximum flow stress of the SLM-processed Ti-6Al-4 V at strain rates of 1/s, 0.01/s, and 0.001/s and at 600–1000 °C temperatures, with average error of 15 %. The SLM-processed Ti-6Al-4 V flow stresses calculated using the developed constitutive equation are useful as mechanical properties required for the thermal stress analysis of the SLM process of Ti-6Al-4 V and are expected to contribute to improvement of the predictive accuracy of the residual stress and deformation during the SLM process of Ti-6Al-4 V.