Hot Tensile Deformation Behavior of Ti-6Al-4V Titanium Alloy Made by Laser Melting Deposition

Abstract

The combined process of additive manufacturing (AM) and subsequent hot forming technology enables the low-cost and rapid manufacturing of complicated structures with local features that cannot be manufactured monolithically by traditional forming technologies. The thermal deformation properties of as-deposited materials from AM require investigation. In this paper, laser melting deposition (LMD) was used to prepare as-deposited Ti-6Al-4V samples; high-temperature tensile tests for as-deposited titanium alloy were performed at different strain rates (0.001 s−1, 0.005 s−1, 0.01 s−1) and temperatures (650 °C, 700 °C, 750 °C) using the electrically assisted high-temperature tensile test system. The results show that the material’s flow stress level was negatively correlated with temperature and positively correlated with strain rate. EBSD and TEM were used to characterize the microstructure of the samples. The acicular martensite in the original material began to disintegrate under the influence of high-temperature tension, coarsening the lamella and splitting the boundary. The proportion of high-angle grain boundaries after deformation increased significantly from 81.4% to 87.5–90.7%. The results of the micromorphology observations indicate that the micro-deformation mechanism for deposited Ti-6Al-4V samples at high temperatures is mostly discontinuous dynamic recrystallization and dynamic spheroidization.