Fabricating a bulk FCC Hf by a combination of high-energy ball milling and spark plasma sintering

A face-centered-cubic (FCC) hafnium (Hf) in bulk was fabricated by a combination of high-energy ball milling and spark plasma sintering (SPS). The hexagonal-close-packed (HCP) Hf powder as the raw material was transformed into FCC phase during ball milling, and the HCP to FCC transformation also occurred when applying SPS on the ball milled powder. The effects of grain size, impurities and structural instability introduced during high-energy ball milling process on the HCP to FCC phase transformation were discussed. In addition, due to the grain boundary strengthening and second phase strengthening, the hardness of the bulk FCC Hf was greatly increased to above 1200 Hv.