| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 100 === In this study, the Mg97Zn1Mm2(La-rich, Ce-rich misch metal) alloys were casted by vacuum induction melting process. The results show that the yield strength of Mg97Zn1(Mm-La)2 and Mg97Zn1(Mm-Ce)2 alloys were higher than that of the Mg97Zn1Y2 in room temperature, but lower elongation due to hard and brittle second phase. However, the high temperature mechanical properties of Mg97Zn1Y2 alloys with a stable phase of LPSO were greater than Mg97Zn1(Mm-La)2 and Mg97Zn1(Mm-Ce)2 alloys, and the tensile yield strength of Mg97Zn1Y2 alloys were 200MPa at 473K.
An increase in strength was associated with high extrusion rate in Mg97Zn1Y2 alloys by rapidly solidified powder metallurgy (RS P/M) processing, and the LPSO phase was refined by extrusion in Mg97Zn1Y2 alloys.
The compositions of second phase was (La,Ce)(Mg,Zn)12 in Mg97Zn1(Mm-La)2 and Mg97Zn1(Mm-Ce)2 alloys by EPMA and XRD analysis. We could strengthen Mg97Zn1(Mm-La)2 and Mg97Zn1(Mm-Ce)2 alloys by hot rolling at 773K, their yield strength were over 300MPa. The second phase was dispersion strengthening in Mg97Zn1(Mm-La)2 and Mg97Zn1(Mm-Ce)2 alloys, instead precipitation strengthening in Mg97Zn1Y2 alloys.
|
|---|
