Effect of Aging Treatment on Microstructural Evolution and Mechanical Properties of the Electron Beam Cold Hearth Melting Ti-6Al-4V Alloy

Abstract

Ti-6Al-4V (Ti64 or TC4) alloy is widely used in the industrial field. However, there have been few studies of the TC4 alloy melted by electron beam cold hearth melting (EBCHM) technology. Aging treatment has a considerable influence on the secondary α-phase in titanium alloys. Therefore, TC4 alloy melted by EBCHM technology was investigated in this study. The effect of different aging times on the microstructural evolution and mechanical properties of titanium alloy sheets was evaluated. The results showed that, with increase in aging time, the primary α-phase enlarged and grain globularization occurred. In addition, some transformed β-phases disappeared. The strength and Vickers hardness of the heat-treated sheets decreased, while the plasticity increased with increase in aging time, indicating that the mechanical properties developed with evolution of the microstructure. After aging at 560 °C for 2 h, the properties overall were optimal. The type of fracture of the samples was ductile fracture; the dimples became larger with increase in aging time. After heat treatment, the recrystallized nucleus, substructures and HAGBs increased, while the deformed structure and LAGBs decreased. Some grains had rotated following heat treatment, indicating that anisotropy was greatly reduced.

Electrochemical characteristic and microstructure of Ti-6Al-7Nb alloy by centrifugal casting for orthopedic implant based on ageing time variations

“…3 demonstrates that as the heat treatment process and ageing period rise, the primary α phase and the grain globulars steadily increase, but the volume fraction of α/α′ phase remains unchanged considerably (Table 2). The morphological characteristic of phases changed noticeably; many secondary α phases precipitated in the matrix seemed to merge together and develop, and some β phases disappeared, according to previous study [39][40][41]. The coarse α phase can be seen in Fig.…”

Carbon in Commercially Pure Titanium

“…There is a consensus of views [ 7 , 11 , 20 , 30 , 32 , 33 ] that carbon increases the age hardenability of titanium alloys. Yu et al [ 34 ] reported that a slight increase in the content of carbon (from 0.008 to 0.034 wt.%) in the quenched Ti-10V-2Fe-3Al alloy and a decrease in the rate of heating to the aging temperature improves the dispersity of secondary phases formed after quenching and promotes growth in the alloy hardness.…”

Effect of heat treatment on microstructure, mechanical and tribological properties of in-situ (TiC+TiB)/TC4 composites by casting

“…The grain size and nucleation quantity of TC4 alloy are inflluenced by the β heat treatment temperature, and the heat treatment temperature in the α+β region is approximately 100 °C below the phase transition point [30] . The aging process of TC4 alloy involves heating to around 500-600 °C, followed by holding for 4-12 h [31] . Therefore, based on the measured β phase transition point, the two β heat treatment temperatures of 1,050 °C and 1,150 °C were set to study the effect of solution temperature on microstructure and properties.…”