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In this study, the structural evolution of two nanostructured Cu-22 wt pct Ge (Cu-20 at. pct Ge) and Cu-26 wt pct Ge (Cu-24 at. pct Ge) alloys upon mechanical alloying (MA) with subsequent heat treatment was investigated, and the phase transitions were monitored by means of various characterization methods. The findings indicated that, when the MA process continued for some time, a nanocrystalline α-Cu(Ge) solid solution was formed, which partially transformed into an amorphous phase. Further MA processing for 20 hours led to the formation of a disordered nanometric ε-CuGe intermetallic compound with a monoclinic crystal structure. Increased milling time subsequently led to the diminishing of the content of the amorphous phase which transformed into ε-CuGe nanocrystals. Clearly, a nanocrystallization transformation occurred upon ball milling principally on account of the accumulated energy due to the heavy mechanical deformation. Crystallization was also seen to occur at 473 K (200 °C) after annealing the MA-ed powders, leading to the formation of an ordered ε-CuGe intermetallic phase with an orthorhombic structure. The crystallographic relationships between the two disordered and ordered intermetallic phases were also discussed. [ABSTRACT FROM AUTHOR]

Abstract: The formation of Ni–B binary intermetallic compounds was investigated by mechanical alloying (MA) of the Ni-15wt.% B (≈Ni-48at.% B) powder mixture and subsequent heat treatment. It was found that an interstitial Ni(B) solid solution was formed at the early stage of milling, followed by the formation of Ni3B intermetallic compound after 25h of milling. On further milling, the Ni3B transformed to Ni2B and o-Ni4B3 (orthorhombic). Phase transformation during heating of Ni(B) solid solution phase up to 800°C could be represented by Ni(B) → Ni3B → Ni2B. Other intermetallics can be formed by heat treatment of Ni(B) solid solution at temperatures above 800°C. [Copyright &y& Elsevier]