Effect of Fe content on glass-forming ability and crystallization behavior of a (Ti69.7Nb23.7Zr4.9Ta1.7)100−xFex alloy synthesized by mechanical alloying

Abstract

(Ti69.7Nb23.7Zr4.9Ta1.7)100−xFex (x=0, 2, 6, and 10) nanocrystalline, nanocomposite and metallic glass powders were synthesized by mechanical alloying. The glass-forming ability (GFA) and crystallization behavior of the synthesized alloy powders are investigated by X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. With the increased Fe content, the synthesized alloy powders after the steady state milling transform from full nanocrystalline structure for x=0 to nanocomposite structure containing amorphous matrix surrounding nanocrystals for x=2 and 6 and to full amorphous structure for x=10, and thus has the increased enthalpy of crystallization and the increased GFA. The non-isothermal crystallization kinetics is analyzed by the modified Johnson–Mehl–Avrami (JMA) equation. The values of the Avrami exponent imply that the crystallization of (Ti69.7Nb23.7Zr4.9Ta1.7)100−xFex nanocomposite/metallic glass powders with x=6 and 10 is governed by diffusion-controlled three and two-dimensional growth, respectively. Moreover, the crystallized bulk alloys consolidated from the synthesized alloy powders have different crystallized phases, microstructures and mechanical properties. The increased GFA with the increased Fe content could be explained by the total number of intermetallics present in the milled powders, appropriate atomic-size mismatch and large negative heat of mixing among constituent elements.