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Ningbo, China

Wang J.,Zhejiang University | Wang J.,China Ordnance Academy | Zhu X.,China Ordnance Academy | Wang R.,China Ordnance Academy | And 3 more authors.
Journal of Rare Earths | Year: 2011

Age hardening, microstructure and mechanical properties of Mg-xY-1.5MM-0.4Zr (x=0, 2, 4, 6 wt.) alloys (MM represents Ce-based misch-metal) were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the formed precipitates being responsible for age hardening changed from fine hexagonal-shaped equilibrium Mg12MM phase to metastable β′ phase with bco crystal structure when Y was added into Mg-1.5MM-0.4Zr alloy, and the volume fraction of precipitate phases also increased. With the increase of Y content in Mg-Y-1.5MM- 0.4Zr alloys, it was found that the age hardening was enhanced, the grain sizes became finer and the tensile strength was improved. The cubic-shaped β-Mg24Y5 precipitate phases were observed at grain boundaries in Mg-6Y-1.5MM-0.4Zr alloy. It was suggested that the distribution of prismatic shaped β′ phases and cubic shaped β-Mg 24Y5 precipitate phases in Mg matrix might account for the remarkable enhancement of tensile strength of Mg-Y-MM-Zr alloy. It was shown that the Mg-6Y-1.5MM-0.4Zr alloy was with maximum tensile strength at aged-peak hardness, UTS of 280 MPa at room temperature and 223 MPa at 250°C, respectively. © 2011 The Chinese Society of Rare Earths.

Wang J.,China Ordnance Academy | Zhu X.-R.,China Ordnance Academy | Xu Y.-D.,China Ordnance Academy | Wang R.,China Ordnance Academy | And 2 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2014

The effects of rare-earth Ce and Y on the melting, microstructure and mechanical properties of AZ80 Mg alloys were investigated by elementary analysis, mechanical properties examination, XRD, SEM and TEM. The experimental results show that the content of Fe decreases obviously during alloy melting, and the melting time is shortened when Y is added into AZ80. The as-cast microstructure of AZ80 alloys is refined, and needle-like Al11Ce3and block-like Al2(Y, Mn) phases generate at grain boundary when 1%Ce and 1%Y (mass fraction) are added into AZ80 alloys. After extrusion, the coarsening of recrystallized grain is depressed by Al-RE phases impeding motion of dislocation at grain boundary. And after extrusion+T5(177°C, 0-30 h) heat-treatment, the maximum tensile strength of AZ80 alloy containing 1%Y is obtained with ultimate tensile stress of 390 MPa and yield stress of 250 MPa.

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