Abstract
Field assisted sintering technology (FAST), also known as spark plasma sintering (SPS), is increasingly utilised to process powders/particulates of engineering alloys and metal-based composite materials. FAST is currently extensively used at laboratory scale by research institutes and universities as a rapid and cost‑effective process to consolidate powders. This includes investigating new alloy compositions and material combinations, improving established materials’ properties, and consolidating materials considered challenging/impossible through conventional sintering techniques. FAST is gaining traction for industrial applications with possible benefits as an alternative to hot isostatic pressing or conventional melt-wrought processing. FAST preform complexity is improving and near-net-shape components are becoming a possibility. Demonstrator components for the aerospace and automotive sectors, including aeroengine blades, brake callipers and rocker arms, have been produced from titanium alloy powders. FAST has also been demonstrated as an effective intermediate step for consolidating a range of feedstocks, including recycled materials, into shaped billets that can be further processed to refine shape and/or properties. Hybrid processes such as FAST‑forge and FAST‑DB have been developed that can produce affordable titanium components with forged properties. This paper presents the current status, emerging developments, and challenges of FAST for titanium-based powders and particulates.
Highlights
BackgroundTitanium alloys have an excellent combination of properties that makes them desirable for applications in many industries
The Ti-6-4 rocker arms forged from Field assisted sintering technology (FAST) bars gave the expected 40% mass reduction and the shaped FAST preforms gave a 55% reduction in material wasted as flash, see Figure 3b
Further work needs to address concerns around swarf cleanliness, contamination, and variability. Whilst it remains unlikely the safety conscious aerospace sector will adopt recycled swarf FAST components for safety critical dynamically loaded applications, there are promising signs that titanium alloy swarf could be a lowcost feedstock for the manufacture of non-safety critical components via processes such as FAST, FAST-forge, and FAST-DB
Summary
Titanium alloys have an excellent combination of properties that makes them desirable for applications in many industries. Several studies have utilised lower temperature and shorter processing times to produce UFG, nanoscale, or bimodal microstructures [25,26,27,28], which typically requires using fine powders or extensive milling; high (compressive) strengths are frequently achieved but with (significantly) reduced ductility. Successful near‐net shaping of γ-TiAl blades shows FAST is a viable route to assist in overcoming these barriers Combining this with the alloy developed by Voisin et al [43], which has excellent mechanical properties at room/high temperatures after a single FAST cycle, may offer significant benefits.
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