Heat Treatment, Impact Properties, and Fracture Behaviour of Ti-6Al-4V Alloy Produced by Powder Compact Extrusion

Abstract

The mechanical properties of titanium and titanium alloys are very sensitive to processing, microstructure, and impurity levels. In this paper, a blended powder mixture of Ti-6Al-4V alloy was consolidated by powder compact extrusion that involved warm compaction, vacuum sintering, and hot extrusion. The as-processed material with an oxygen content of 0.34 wt.% was subjected to various annealing treatments. The impact toughness of heat-treated material was determined using Charpy V-notch impact testing at room temperature. An emphasis was placed on establishing a relationship among fracture behaviour, microstructure, and the resulting properties of tested material. From the results, it is apparent that the highest impact toughness value of 19.3 J was achieved after α/β annealing and is comparable with typical values given in the literature for wrought Ti-6Al-4V. In terms of fracture behaviour, it is quite apparent that the crack propagation behaviour of powder-produced material is rather complex compared with the limited amount of data reported for ingot counterparts.

Processing, microstructure, properties and fracture behaviour of Ti–6Al–4V manufactured from pre-alloyed powder

“…The value of Charpy impact toughness (21 J) for the material produced in this study is superior when compared with all the data accumulated by TPC processing to date. This shows that the level of enhancement that can be attained by reducing the oxygen content to 0.22 wt-% is higher than that obtained for the heat-treated material [10-12] and one that has an oxygen content of 0.34 ± 0.005 wt-%. In other words, preparation of the material from a high oxygen Ti–6Al–4V blended powder mixture followed by heat treatment in α + β phase field can provide a specific level of improvement although for any further enhancement, a drop in oxygen content would be essential.…”

“…In previous studies [9][10][11][12], successful manufacturing of blended elemental Ti-6Al-4V alloy from relatively high oxygen containing hydride/dehydride (HDH) titanium and master alloy powders has been demonstrated using TPC processes such as powder compact hot pressing plus extrusion or sintering plus extrusion. From mechanical property data collated to date for blended elemental Ti-6Al-4V alloy, it is clear that depending on the oxygen content, processing conditions and post-heat treatments, a reasonable balance of mechanical properties (such as strength, hardness, ductility and toughness) can be achieved [9][10][11][12]. However, in the majority of these cases, the utilisation of the corresponding material produced from blended powders might be limited to 'fit for purpose', non-critical applications, due to the effects of high oxygen.…”

Thermomechanical Simulations of Residual Stresses and Distortion in Electron Beam Melting with Experimental Validation for Ti-6Al-4V

“…For instance, in Figure 23c, it can be seen that layer-2 receives several heat cycles due to electron beam scans on subsequent layers as compared to layer-8, which only receives 2 heat cycles (see Figure 23d). Usually, the higher heat accumulation and rapid extraction of heat favor the higher concentration of the beta phase and vice versa for the alpha phase [35,36]. Therefore, in Figure 23a, more β phase and wider α grains could be observed.…”