a b s t r a c tIn this paper, the feasibility of producing Ti-6Al-4V with a range of wrought-like microstructures and mechanical properties via a novel powder metallurgy (PM) process with simple heat treatments is investigated. The wrought-like PM Ti-6Al-4V is obtained by sintering blended elemental (BE) powder in a hydrogen atmosphere, followed by conventional Ti-6Al-4V heat treating profiles. This is achieved without resorting to energy-intensive thermomechanical processing (TMP) that is compulsory for producing high performance titanium alloys via wrought processing or traditional powder metallurgy.Currently, wrought processing is the state of the art for producing Ti alloys with microstructures and mechanical properties necessary for critical applications. However, wrought Ti is prohibitively expensive for use in most commercial applications, due to the multi-step, energy-intensive, thermomechanical processing (TMP) routes used. Additionally, many Ti components have high buy-to-fly ratios. Because of this, powder metallurgy (PM) has long been sought as a means to reduce the cost of Ti alloys, owing to its near-net-shape (NNS) capabilities [1]. However, low-cost PM Ti typically has relatively poor mechanical properties. Additional processes can be incorporated into traditional PM to improve mechanical properties, such as pre-alloying the powder, pressure-assisted sintering, and thermomechanical work. However, these processes significantly increase cost, thereby offsetting the economic benefits of using PM [2]. Therefore, the key for any successful alternative to wrought processing is to maximize the performance-to-cost ratio of Ti alloys by producing wrought-like microstructures and mechanical properties using low-energy materials and processing routes.Specifically to PM Ti, the key to achieve mechanical properties that can match that of wrought Ti while maintaining the low-cost advantage is to find a way to produce wrought-like microstructures without using pressure-assisted sintering processes or relying on TMP, which is energy-intensive and incompatible with the NNS nature of PM. This objective can be achieved only by using low-cost powder, blended elemental alloying, near-net-shape compaction, and pressure-less sintering processes that can deliver the desired microstructures in the as-sintered or heat-treated state. Achieving this goal would be a breakthrough that could transform the Ti industry.Hydrogen sintering and phase transformation (HSPT) is a new, low-cost, blended elemental (BE), press and sinter process for producing titanium alloys from hydrogenated Ti powder. The current authors have previously demonstrated the ability of HSPT to produce Ti-6Al-4V with over 99% relative density, an ultrafine grain (UFG) microstructure, and extraordinary mechanical properties in the as-sintered state [3][4][5][6][7]. Using hydrogenated Ti powder has been shown in the literature to have several benefits as a PM Ti feedstock, including improved densification behaviour [8]. However, the key innovation of HSPT is th...

Traditionally, titanium alloys with satisfactory mechanical properties can only be produced via energy-intensive and costly wrought processes, while titanium alloys produced using low-cost powder metallurgy methods consistently result in inferior mechanical properties, especially low fatigue strength. Herein, we demonstrate a new microstructural engineering approach for producing low-cost titanium alloys with exceptional fatigue strength via the hydrogen sintering and phase transformation (HSPT) process. The high fatigue strength presented in this work is achieved by creating wrought-like microstructures without resorting to wrought processing. This is accomplished by generating an ultrafine-grained as-sintered microstructure through hydrogen-enabled phase transformations, facilitating the subsequent creation of fatigue-resistant microstructures via simple heat treatments. The exceptional strength, ductility, and fatigue performance reported in this paper are a breakthrough in the field of low-cost titanium processing.

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