Internal friction evidence of phase transformations of Fe-Al elemental powders during sintering process

Abstract

Internal friction combined with SEM, DSC and XRD measurements was first applied so far to investigate phase transformation behaviors of Fe-Al elemental powders. Special attentions are concentrated on the influence of mechanical ball-milling on microstructure transition during sintering process. A tailored solid solution degree of the Fe-Al powder mixture can be obtained by mechanical ball-milling for different time. Four typical internal friction peaks are observed as termed P1, P2, P3 and P4 peak respectively for Fe-Al ball-milled powder compact. While for no ball-milled one, only P2 and P4 peaks appear. It was rationalized that the four internal friction peaks are probably associated with the formation of FeAl3, Fe2Al5, FeAl2 and FeAl respectively because of solid diffusion reaction during sintering process. In addition, increasing ball-milling time results in enhancement of solid solution degree owing to refined powder particle and substructure as well as increased solid defect density and interfacial area, and thus phase transformation and corresponding internal friction peaks shift to a lower temperature. The absence of two internal friction peaks in no ball-milled one is ascribed to lower solid solution degree.