S.M. Hao

Intermetallics and phase relations of Mg-Zn-Ce alloys at 400 °C

Abstract The crystal structures, compositions and phase relations of the intermetallics of Mg-Zn-Ce system in the Mg-rich corner at 400 °C were identified through equilibrium alloy method. For Mg-Zn-Ce system, there is a linear ternary compound ( T phase), whose chemical formula is (Mg 1- x Zn x ) 11 Ce. The range of Zn content in T phase is from 9.6% to 43.6% (molar fraction). The crystal structure of T phase is C -centered orthorhombic lattice with lattice parameters of a =0.96-1.029 nm, b =1.115-1.204 nm, c =0.940-1.015 nm. And the lattice parameters of T phase are decreasing a little with increasing Zn content. According to the results of composition and crystal structure, the maximal solubility of Zn in Mg 12 Ce is about 7.8% (molar fraction), and the chemical formula of the solid solution can be identified as (Mg 1- x Zn x ) 12 Ce. The isothermal section of Mg-Zn-Ce system in Mg-rich corner at 400 °C was constructed.

Partial phase relationships of Mg-Zn-Ce system at 350 °C

Abstract The alloys were prepared in Mg-rich corner of Mg-Zn-Ce system. Partial phase equilibrium relationships of these alloys at 350 °Cwere identified by using scanning electron microscopy(SEM), electron probe microanalysis(EPMA), X-ray diffraction(XRD) analysis and selected area electron diffraction(SAED) pattern analysis of transmission electron microscopy(TEM). Partial isothermal section of Mg-Zn-Ce system in Mg-rich corner was identified. The results show that there is one ternary compound (T-phase) in Mg-Zn-Ce system. The T-phase is a linear ternary compound in which the content of Ce is about 7.7% (molar fraction); while the content of Zn is changed from 19.3% to 43.6% (molar fraction). The crystal structure of T-phase is C-centered orthorhombic. In addition, one two-phase region of Mg+T-phase and one three-phase region of Mg+T-phase+MgZn(Ce) exist in the Mg-rich corner of Mg-Zn-Ce system at 350 °C.

Isothermal Section Of Mg-Zn-La System in Mg Rich Corner at 350°C

Alloys of Mg-Zn-La system in Mg rich corner at 350°C have been prepared in this study. Scanning electron microscopy (SEM), electron probe microanalysis with energy dispersive X-ray spectroscopy (EPMA-EDS), and X-ray diffraction (XRD) have been used to identify the phase equilibrium and the composition of each phase in the alloys. As a result, the isothermal section of Mg-Zn-La system in Mg rich corner at 350°C has been determined. The result shows that, in addition to some binary phases, there exists a linear ternary compound called T-phase in Mg-Zn-La system at 350°C, in which the La content is about 8 at. pct ±0.4 at. pct and the Zn content is 8 at. pct–48 at. pct. The T-phase has a C-centered orthorhombic crystal structure, and the lattice parameters are a=0.965–1.020 nm, b=1.121–1.142 nm, c=0.950–0.977 nm.

Phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350°C

Abstract The phase eqyilibria in the Mg-rich corner of the Mg-Zn-La system at 350°C have been investigated by scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. It has been shown that the linear compound (Mg, Zn) 17 La 2 existed in the Mg-Zn-La system at 350°C. The linear compound (so-called T phase) was with the C-centred orthorhombic crystal structure induced by the solution of significant quantities of the third element. The three-phase region α(Mg) + MgZn(La) + T and the two-phase region composed of the α(Mg) and the linear-compound T phase existed in the Mg-rich corner of the Mg-Zn-La system at 350°C.

Phase equilibria in Co-rich region of Co−Ti−Ta system

Abstract The phase equilibria in Co-rich region of Co-Ti-Ta system were studied. The microstructure and XRD analysis together with EDS determination show that L 1 2 type Co 3 Ti phase and Laves_C36_Co 3 Ta phase get equilibrium with α -Co phase from 1 000 to 1 200 °C. The Co 3 Ti phase possesses a solubility of Ta higher than 10%, and the addition of Ta stabilizes the Co 3 Ti phase. The isothermal sections of the Co-Ti-Ta system in the Co-rich region at 1 000, 1 100 and 1 200 °C were constructed according to the result.

Abnormal refining of stepped-annealing microstructure in an Al alloy containing low copper and high zinc

When the recrystallization of spinodal microstructure in an A1-39Zn-2Cu(at.%) alloy was investigated, the recrystallization of equilibrium microstructure of stepannealing in the alloy was studied first. In the present study, the following treatment of stepped-annealing was carried out (Treatment A), as shown in Fig. 1. The annealed sample was cold rolled by 50%, and kept at the temperature of 200 ◦C for 1 h, then water quenched. It is found that an abnormal refining of Zn phase occurred, as shown in Fig. 2. The annealed microstructure prior to the cold-plastic deformation is shown as Fig. 2a. The dark granular particles in a relatively large size that were distributed throughout the matrix phase were Zn phase, whose volume fraction was about 40%, and there also existed the Cu-rich phase of high bright granular particles in smaller size and less quantity. In the cold-rolled microstructure, the second phase underwent the plastic deformation, and grains were elongated along the rolling direction in some areas, and (Fig. 2b). The change in the matrix during reheating cannot be observed under optical microscope, while the second phase had a remarkable change, and was transformed to the finer particles (Fig. 2c). If the deformed grains were transformed into equiaxial and finer ones, it belongs to the normal recrystallization. However, the evolution of the Zn phase here is distinctly different from that. The evolution of Zn phase in this way consequentially leads to an increase of the boundary energy. Therefore, it is necessary to make the reason of this unusual evolution clear. Firstly, the microstructure evolution was studied by holding the specimen at temperatures ranging from 50 to 200 ◦C for 1 h, and the microstructures observed by scanning electron microscope (SEM) are shown as Fig. 3. When the sample was kept at 50 ◦C for 1 h, besides the elongated Zn phase along the rolling