Elemental powder mixtures with the composition of Mo-12Si-10B-3Zr-0.3Y (at%) were milled in a planetary ball mill using hardened stainless-steel milling media under argon atmosphere. Effects of milling time, milling speed, process control agent, ball-to-powder ratio and milling ball size on the mechanical alloying processes were investigated from the points of morphology, internal structure, grain size, microstrain, phase constituent and dissolution of solute atoms. It is shown that under all conditions, the microstructural evolutions of mechanically milled powder particles are similar. The morphological evolution can roughly be divided into five stages: individual particle, irregular blocky composite particle, flakeshaped particle, agglomerate and single particle. The internal structure generally undergoes five stages: individual particle, coarse lamellar structure, fine lamellar structure, non-uniformly mixed structure and plum-pudding structure. Regardless of exceptional cases, the grain size of Moss decreases and its microstrain increases with the increase in milling time. Si and Zr atoms are dissolved into Mo gradually with the progress of milling. However, the evolutionary rates change significantly with milling conditions. The most significant influencing factor among different milling conditions is the input power from the mill to the powders, which plays a decisive role in the milling process.
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