Font Size: a A A

The Compounds And Phase Equilibria In The High Mg Side Of The Mg-Zn-Ce System

Posted on:2009-11-22Degree:MasterType:Thesis
Country:ChinaCandidate:X M LiFull Text:PDF
GTID:2131360308979672Subject:Materials science
Abstract/Summary:PDF Full Text Request
As one kind of new advanced materials, Mg-based alloys with additions of rare earth elements have been paid to more attentions. Mg-based alloys own excellent properties, and the special structures of rare earth elements also play an important role in improving the intensity of magnesium based alloys. Many Mg-Zn-RE alloys have been widely used in many fields. However,up to now, the phase diagrams of the Mg-Zn-Ce system could not provide enough information to guide alloy design. Design of the new alloys and improvement on the properties of the existed alloys were restricted. So it is very important to study on the compounds and the related phases equilibria in the Mg-rich corner of the Mg-Zn-Ce system.By means of conventional equilibrated alloy methods, compositions and structure of the compounds and the related phase equilibria in the Mg-rich corner of the Mg-Zn-Ce system have been researched through the microstructure observation, electron probe microanalysis, X-ray diffraction and electron diffraction on the alloys of Mg81Zn17.5Ce1.5,Mg90Zn5Ce5,Mg88Zn2Ce10,Mg58Zn37Ce5,Mg93Ce5Zn2,Mg80Ce5Zn15,Mg92Ce7Zn1,Mg86Ce3.5Zn10.5 Mg87Zn8Ce5 treated at 350,300 and 200℃.It has been shown that no liquid exists, and only solid state phase equilibria exist in the Mg-rich corner of the Mg-Zn-Ce system below 350℃. At 350℃, the linear compound Mg92-xZnxCe8 (T phase) with 8at% Ce and continued changing of Zn content exists in the Mg-rich corner of the Mg-Zn-Ce system. The composition range of the T phase is Mg:48.8~73.4at%, Zn:2.3~43.6at%, Ce:7.64~7.86 at%. The T phase has a C-centred orthorhombic crystal structure. The broad two-phase region (Mg)+T and the three-phase region (Mg)+T+MgZn(Ce) exist in the Mg-rich corner of the Mg-Zn-Ce system at 350℃. The two-phase region (Mg)+Mg12Ce(Zn) also exists in the Mg-rich corner of the Mg-Zn-Ce system at 350℃.Also it has been shown that the linear compound T could exist stably at the temperature range of 350~200℃. The phase regions of (Mg)+Mg12Ce(Zn), (Mg)+T and (Mg)+ MgZn(Ce) +T also exist in the Mg-rich corner of the Mg-Zn-Ce system at 300℃and 200℃, and the shape of the three phase region is almost the same at 350~200℃.
Keywords/Search Tags:Mg-Zn-Ce, rare earth, ternary linear compound, crystal structure, phase equilibrium, isothermal section
PDF Full Text Request
Related items