On microstructural evolution and mechanical properties of Ti-5Al-5V-5Mo-3Cr alloy synthesised from elemental powder mixtures

Abstract

In this paper, we explored to prepare a multi-compositional titanium alloy, Ti-5Al-5V-5Mo-3Cr (Ti-5553), by powder compact extrusion from elemental powder mixtures, and investigate the microstructure variation during the synthesising process and after post heat treatments and the changes of mechanical properties. XRD, OM and SEM were used to analyse the phase constitutions and microstructures of the Ti-5553 alloy at different processing conditions, and tensile tests were conducted to examine their mechanical properties. The results showed that a homogeneous Ti-5553 alloy was successfully produced by powder compact extrusion from the powder mixtures, β phase was mainly contained in the hot-pressed and 1200°C-extruded Ti-5553 alloy and had an equiaxed microstructure. Different types of α phase precipitated from the β matrix after heat treatment, and this significantly changed the microstructures and improved the mechanical properties of the extruded Ti-5553 alloy, with yield strength of 1250 MPa and ultimate strength of 1300 MPa for the alloy treated at 675 ºC for 2 h, and the ductility of about 6.1% for the alloy treated at 780 ºC for 2 h.

Comparison of the Cracking Behavior of Powder Metallurgy and Ingot Metallurgy Ti-5Al-5Mo-5V-3Cr Alloys during Hot Deformation

“…Much finer microstructure can be found in the PM alloy (Figure 1a showing an average grain size of 100 μm) than the IM alloy (Figure 1b, showing an average grain size of 1000 μm), and some residual pores can be identified in the microstructure of the PM alloy. A typical β grain matrix can be observed in, both, the PM and the IM alloy, and the IM alloy was composed of a large number of dispersed α phase, which was spread over a β matrix, while only a small amount of the agminated α precipitates could be seen in the PM alloy, mainly distributed along β grain boundaries [19,25].…”

“…The green compact was heated up, rapidly, in an induction coil to the target temperature of 1250 °C to 1300 °C, in the protective argon atmosphere, followed by a hot-pressing under uniaxial pressure. Hereinafter, the billet was cooled down to room temperature in the flow argon protection, the detailed processes of this rapid consolidation approach have also been described elsewhere [18,19,24]. The consolidated PM Ti-5553 alloy billet had a diameter of 58 mm and a relative density of 98%.…”

“…The powder metallurgy (PM) approach has been verified to be a cost-effective processing technique to produce titanium alloy products that meet the requirement of the industrial applications, with additional benefits, such as the manufacture of near-net-shape parts and optimization of the microstructure [13,16,17]. Furthermore, utilizing rapid consolidation processing methods, such as hot pressing and powder forging, instead of conventional vacuum sintering and hot isostatic pressing (HIP) processes, the titanium alloy products can be produced in a much shorter process and their costs can be reduced significantly [18,19].…”

The Investigation on Flow Behavior of Powder Metallurgy Ti-10V-2Fe-3Al Alloy Using the Prasad Stability Criterion

“…The initial microstructure of Ti-10-2-3 alloy compact shown in Figure 2 is characteristic for b or near b titanium alloys cooled slowly from the b phase field. [12] Precipitations first appear inside b grains and on their boundaries and then grow to coarse lamellas. Also, acicular a grains arranged perpendicular to each other were noticed.…”

“…Recently, many researchers have been focused on developing a cost-effective technique to obtain titanium products from consolidated powders. Different approaches, such as hot isostatic pressing of gas-atomized powder, [9,10] hot or cold pressing followed by sintering of blended elemental powders (BEPM), [11][12][13][14] and novel selective laser melting techniques, are proposed to prepare titanium alloy with specified chemical composition. [15][16][17] Regardless of the methods mentioned previously, materials obtained by PM techniques have high relative density and similar mechanical properties as titanium alloys with an equivalent chemical composition produced by conventional route.…”