Experimental Investigation of the Ce-Mg-Mn Isothermal Sectionudat 723 K (450°C) via Diffusion Couples Technique

摘要

The isothermal section of the Ce-Mg-Mn phase diagram at 723 K (450°�C) was establishedudexperimentally by means of diffusion couples and key alloys. The phase relationships in theudcomplete composition range were determined based on six solid–solid diffusion couples andudtwelve annealed key alloys. No ternary compounds were found in the Ce-Mg-Mn system atud723 K (450°C). X-ray diffraction and energy-dispersive X-ray spectroscopy spot analyses were used for phase identification. EDS line-scans, across the diffusion layers, were performed to determine the binary and ternary homogeneity ranges. Mn was observed in the diffusion couplesudand key alloys microstructures as either a solute element in the Ce-Mg compounds or as a pure element, because it has no tendency to form intermetallic compounds with either Ce or Mg. The fast at. interdiffusion of Ce and Mg produces several binary compounds (CexMgy) during the diffusion process. Thus, the diffusion layers formed in the ternary diffusion couples were similar to those in the Ce-Mg binary diffusion couples, except that the ternary diffusion couples contain layers of Ce-Mg compounds that dissolve certain amount of Mn. Also, the ternary diffusionudcouples showed layers containing islands of pure Mn distributed in most diffusion zones. As a result, the phase boundary lines were pointing toward Mn-rich corner, which supports the tendency of Mn to be in equilibrium with all the phases in the system.