Effect of high-energy ball-milling on the spark plasma sinterability of ZrB2 with transition metal disilicides

Abstract

A wide suite of powder mixtures of ZrB2 with five different additions of transition metal disilicides (MeSi2; 5, 17.5, or 30 vol% MoSi2; 17.5 vol% TaSi2; or 17.5 vol% ZrSi2) were prepared by high-energy ball-milling (HEBM) for different times, and their optimal densification temperatures were evaluated by dilatometric spark-plasma-sintering (SPS) tests to compare their sinterability. SPS densification tests at the so-determined optimal densification temperatures were also performed in selected cases. It was found that HEBM progressively enhanced the sinterability, especially once the ZrB2 particle sizes were refined to the ultrafine range or below (<250 nm). It was also observed that the sinterability was enhanced (i) with the greater addition of MeSi2, and (ii) with the lower refractoriness of the MeSi2. Nonetheless, under long-time HEBM, the addition of harder, more refractory MeSi2 or of softer, less refractory MeSi2 is equally effective in terms of sinterability, both enabling low-temperature densification (SPS at ∼1200 °C).