Phase Equilibria of the Mn-Si-Zn System at 600 °C

Abstract

The phase equilibria at 600 °C of the Mn-Si-Zn system were investigated by using nineteen equilibrated alloys and two diffusion couples. The alloys were prepared by melting the pure elements in the alumina crucibles encapsulated in quartz tubes. The samples were examined by means of optical microscopy, X-ray diffraction, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The experimental results showed no existence of ternary compounds in the Mn-Si-Zn system. The binary compound Mn5Si2, the existence of which is controversial in the literature, were not observed at 600 °C. A massive phase transformation for (γMn) was observed due to its slow quenching. In addition, the controversial e-phase region was studied. The existence of e1 was confirmed through a diffusion couple method. Though the existence of e2 (another controversial subdivision of the e phase) was not confirmed, it is assumed to exist, taking into account the difference in the observed mechanical properties of the Mn-Zn binary alloys. The solubility of Zn in R-Mn6Si, ν-Mn9Si2, Mn3Si, Mn5Si3, MnSi, and Mn11Si19 was measured to be 1.3, 0.8, 0.5, 0.8, 0.5, and 0.2 at. pct Zn, respectively. The solubility of Si in (βMn), (γMn), e, and liquid was determined to be negligible.