Thermodynamic Re-Assessment of the Mn-La Binary System

Abstract

In this work, eleven Mn-La alloys were investigated experimentally by means of thermal analysis. The temperatures of the invariant reactions in the Mn-La binary system were determined. To confirm whether the liquid miscibility gap exists in the Mn-La system, one key alloy (Mn72La28) was prepared and then checked by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Microstructure observation and composition analysis indicated the nonexistence of the liquid miscibility gap. Based on the experimental results obtained in the present work and the critical review of the available experimental data in the published literature, a set of self-consistent thermodynamic parameters for the Mn-La system was obtained using the CALPHAD method by thermodynamic optimization of the selected experimental data.

Development of thermodynamic database of the Mn‐RE (RE = rare earth metals) binary systems

“…Phase equilibria of the Mn‐Ho binary system were studied experimentally, [41,47] and were calculated by Wang et al., [49] Kim et al., [20] and Wang et al [24] . According to the reported experimental data and calculations, five Mn‐RE (RE = La, Nd, Gd, Dy, and Ho) binary systems were reassessed in our group [21–24] . The calculated results are consistent well with the experimental data.…”

“…The calculated Mn‐Lu binary phase diagram is shown in Figure 24, considering the systematic trend in the Mn‐RE binary phase diagrams according to our previous calculations of the Mn‐RE (RE = La, Nd, Gd, Dy, and Ho) systems [21–24] . As can be seen, there are three stable intermetallic compounds, Mn 5 Lu, Mn 23 Lu 6 , and Mn 2 Lu in the Mn‐Lu binary system.…”

“…In our previous work, [21–24] phase equilibria of the Mn‐RE (RE = La, Nd, Gd, Dy, and Ho) binary systems were redetermined experimentally. Therefore, the proposed temperatures of the invariant reactions were obtained in this work by mainly taking into account the systematic trend mentioned in Section 3.3 above and combining the formation temperatures of the Mn‐RE intermetallic compounds, [21–24] which are different from that proposed by Kim et al [19] …”

“…Consequently, it is not unreasonable to infer that this systematic trend also holds in the Mn‐RE (RE = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y) binary systems. In our previous work, phase equilibria and thermodynamic properties of five Mn‐RE (RE = La, Nd, Gd, Dy and Ho) binary systems [21–24] were reassessed based on the experimental results. In order to discuss the systematic trend, these assessment results are presented in Figure 36.…”

“…In our previous work, five Mn‐RE (RE = La, Nd, Gd, Dy, and Ho) binary systems were assessed using the substitutional solution model to describe the liquid phase [21–24] . The Mn‐La binary system was investigated by several authors [25–32] and thermodynamic calculations of this binary system were performed [18,21,33] . The Mn‐Nd binary system was evaluated, [34–40] and three intermetallic compounds Mn 17 Nd 2 , Mn 23 Nd 6 , and Mn 2 Nd were confirmed.…”