Characterization of nanocrystalline CoCrFeNiTiAl high-entropy solid solution processed by mechanical alloying

The equiatomic multicomponent CoCrFeNiTiAl high-entropy solid solution alloy was synthesized by mechanical alloying (MA). The effects of milling duration and subsequent annealing on the structure and morphology evolution were investigated. Supersaturated BCC and FCC solid solutions appear when the blended powder is ball milled more than 18 h. The 30 h ball milled alloy powder shows excellent chemical homogeneity and refined morphology with mean particle size of less than 5 mu m. The microscaled particles are actually hard agglomerations of nanoscaled crystallines with crystal size of about 40 nm. The phase composition transforms to two BCC solid solutions when the 30 h mechanically alloyed powder was annealed at 600 degrees C for 1 h. The simple solid solution structure can be maintained even after the alloy was annealed at 1000 degrees C. The 30 h milled alloy powder was subsequently consolidated by spark plasma sintering (SPS) at 800 degrees C for 10 min. The sintered sample Exhibits 98% in relative density and 432 HV in Vickers hardness. (C) 2009 Elsevier B.V. All rights reserved.