A study on the sintering of ultrafine grained tungsten with Ti-based additives

Abstract

Tungsten (W) is a brittle material at room temperature making it very difficult to fabricate. Although the lack of ductility remains a difficult challenge, nano-sized and ultrafine grain (UFG) microstructures offer potential for overcoming tungsten's room temperature brittleness. One way to manufacture UFG W is to compact and sinter nanosized W powder, however, it is a non-trivial task to control grain growth during sintering. In an effort to inhibit grain growth, the effect of Ti-based additives on the densification and grain growth of nano-W powders was investigated in this study. The addition of 1 wt.% Ti into tungsten led to more than a 63% decrease in average grain size of sintered samples at comparable density levels. It was also found that sintering in Ar yielded a finer grain size than sintering in H 2 at similar densities. Compared to conventional high temperature sintering, a lower temperature sintering cycle for a longer hold time resulted in both near-full density and fine grain size. The roles of the Ti additive include not only the inhibition of grain growth, but also the potential absorption of oxygen from W particles.

Powder Metallurgy Route to Ultrafine‐Grained Refractory Metals

“…[ 77,116,137 ] b) Grain coarsening index (from initial particle size to bulk grain size) versus relative density, for comparison of the differently sized pure W powders. [ 50,77,88,91,98,117,125,130,135,136,138–141 ] c) Comparison of grain size of pure W versus various ODS W, plotted with relative density. [ 47,50,71,75,117,133,142–149 ]…”

“…[77,116,137] b) Grain coarsening index (from initial particle size to bulk grain size) versus relative density, for comparison of the differently sized pure W powders. [50,77,88,91,98,117,125,130,135,136,[138][139][140][141] c) Comparison of grain size of pure W versus various ODS W, plotted with relative density. [47,50,71,75,117,133,[142][143][144][145][146][147][148][149] Field-assisted sintering utilizes the external pressure, electric, microwave, and coupled multi-physic fields to improve sintering.…”

“…Figure 6. a) Dependence of sintering temperature of W powder on particle size expressed by the scaling law, along with trajectory fitted by experimental results from previous literatures [77,116,137]. b) Grain coarsening index (from initial particle size to bulk grain size) versus relative density, for comparison of the differently sized pure W powders [50,77,88,91,98,117,125,130,135,136,[138][139][140][141]. c) Comparison of grain size of pure W versus various ODS W, plotted with relative density [47,50,71,75,117,133,[142][143][144][145][146][147][148][149].…”

W–Cu composites with submicron- and nanostructures: progress and challenges

“…Ren et al studied the effect of Ti addition on the densification and grain growth of W powders in the sintering process 59 . The results showed that with 1 wt.% Ti addition, the mean grain size of W was decreased by 63% compared with that without Ti but with the same sintering density.…”