Abstract
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.
Highlights
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
By using TiH2 powder as the feedstock, strides have been made in recent decades towards improving the density and purity of titanium alloys produced by vacuum sintering of relatively inexpensive blended elemental/ master-alloy (BE/MA) powder[6,7,8,9,10,11,12,13,14]
hydrogen sintering and phase transformation (HSPT) is able to produce Ti-6Al-4V with fatigue properties that far exceed what is typical for BE/MA Ti-6Al-4V without incorporating costly post-sintering processing to improve fatigue performance
Summary
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. The high fatigue strength presented in this work is achieved by creating wroughtlike 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. By using TiH2 powder as the feedstock, strides have been made in recent decades towards improving the density and purity of titanium alloys produced by vacuum sintering of relatively inexpensive BE/MA powder[6,7,8,9,10,11,12,13,14] These alloys still have the coarse lamellar microstructure that is typical of PM Ti-6Al-4V, which is detrimental to mechanical properties, fatigue strength[15]. Especially globularized/equiaxed and bi-modal microstructures, are known to have excellent fatigue strength in Ti-6Al-4V alloys[19]
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