Microstructure development of Y-Ti-O dispersion strengthened Cu alloys fabricated by mechanical alloying

A Y-Ti-O oxide-dispersion-strengthened (ODS) Cu alloy has been successfully fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Excessive cold-welding during high energy ball-milling was effectively suppressed by mixing TiO2 and pre-alloyed Cu(Y) powders as the raw powders. Microstructural evolutions during the MA and SPS processes and the subsequent annealing were investigated with a focus on the Y-Ti-O nanooxides. The 12 h ball-milling failed to achieve super-saturations of Y, Ti, and O in Cu, which led to the in-situ formation of various types of oversized Y/Ti-rich oxides with very irregular morphologies during the SPS. With a prolonged ball-milling of 48 h, the subsequent SPS + annealing processes can promote a high density precipitation of ultra-fine Y-Ti-O nano-oxides. These nano-oxides were further identified as Y2Ti2O7 mostly, with a high degree of coherency in Cu. Fabricating Y-Ti-O ODS-Cu alloys via MA was thus confirmed to be technically feasible, although the dispersion of nano-oxides desires further improvement.