Effect of spark plasma sintering and reinforcements on the formation of ultra-fine and nanograins in AA2024-TiB2-Y hybrid composites

Abstract

This study reports the influence of sintering mechanism and reinforcement materials on the formation of ultra-fine and nanograins in Al-TiB2-Y nanohybrid composites. The mechanical properties of the composites and their corresponding micro and nanostructures are correlated. The experimental and characterization results revealed that despite the addition of TiB2, the hard and brittle Al3Ti phase formation in the composites was suppressed and hence, their ductility was retained. It was found that yttrium content of 0.3 ​wt% was the optimum amount which created advantageous spark plasma sintering conditions, and the addition of 0.3 ​wt% promoted the formation of bi-modal size grains (ultra-fine and nano) along with micro grains, Ω and other nano precipitates, resulting in a significant enhancement in the composite properties. The formation of ultra-fine and nanograins may be attributed to the combined effect of melting and rapid solidification at necking zones due to Joule's heating and thermo-mechanical fatigue. Among all the sintered composites, the highest hardness (137 HV), ultimate tensile strength (UTS) (496 ​MPa), yield strength (YS) (438 ​MPa) with 15.7% elongation were obtained in the sintered sample reinforced with 1.0 ​wt% TiB2 and 0.3 ​wt% yttrium.