Powder-metallurgy fabrication of ZrB2–hardened Zr3Al2 intermetallic composites by high-energy ball-milling and reactive spark-plasma sintering

A powder metallurgy route combining high-energy ball-milling (HEBM) of elemental powders and reactive spark-plasma sintering (SPS) is proposed for the controlled fabrication novel composites based on a Zr–Al intermetallic matrix hardened with ceramic second-phase. As proof-of-concept, its suitability demonstrated ZrB2–hardened Zr3Al2. Specifically, commercially available ZrH2, Al, B were first combined in molar ratios 2:1:1 to give an intermetallic–ceramic composite nominally formed by ∼76.8 vol.% Zr3Al2 plus 23.2 ZrB2, intimately mixed mechanically activated HEBM form dry shaker milling 30 min, next identifying dilatometric SPS test at 50 MPa pressure that densification window these ∼975–1275 °C. Subsequent tests temperature interval, also 1350 °C, microstructural mechanical characterisations resulting materials, established 1175 °C as optimal temperature. It was identified takes place transient liquid-phase molten it occurs gradually, not abruptly, because most Al disappears flash reacting Zr situ intermetallic. shown combination yields Zr3Al2+ZrB2 fine-grained microstructures essentially multitudinous ZrB2 nanograins dispersed within submicrometre, or nearly grains. Importantly, found be very hard (i.e., ∼11.5 GPa), attributable hardening provided nanograins, fairly tough ∼4.5 MPa·m1/2), therefore potential candidate materials multitude structural–tribological applications. Finally, implications future study are discussed.