Research Of Re And Zr, Ca Effect On Microstructure And Property Of Heat Resistance Mg Alloy

In this paper, under the combined fire-prevent protection of RJ-2 and Be, Mg-Nd-Zr-Zn, Mg-Y-Zr-Zn and Mg-Al-MM-Ca alloys were safely prepared in the open air. By means of optical microscope, scan electron microscope (SEM), electrical probe, effects of Nd, Zr, Y, Ca on microstructure and 250℃ mechanical properties in respective alloy were studied. Microstructure and elevated temperature rupture section of the three alloys were analyzed. Staples of best 250℃ mechanical properties of the three alloys were ascertained. The results are as follows:In Mg-Nd-Zr-Zn alloy, Nd exists in grains and grain boundaries in form of Mg12Nd. With the increase of the additive of Nd, the elevated temperature tensile strength of the alloy is improving and then is not remarkable. When the content of Nd exceeds 2.8%, the elevated temperature plastic is elevated and then reduced. Zr is solid dissolved in Mg and with the increase of the additive of which, the elevated temperature tensile strength and plasticity are all elevated and then reduced. Under the temperature of 250℃, the way in which the alloy ruptures is mainly plastic. The reasonable staple of the alloy is: Mg(balance)-Nd(2.8%)-Zr(0.8%)-Zn(0.35%).In Mg-Y-Zr-Zn alloy, Y exists in grain boundaries in form of Mg24Y5 which dissolve in Mg after heat treatment. With the increase of additive of Y, the elevated temperature tensile strength of the alloy is elevated and the plasticity of the alloy reduced. Under the temperature of 250℃, the way in which the alloy ruptures is mainly plastic including certain brittle fracture. The reasonable staple of the alloy is: Mg(balance)-Y(4.0%)-Zr(0.8%)-Zn(0.35%).In Mg-Al-MM-Ca alloy, Ca mainly solid dissolves in the blended phases of Mg17Al12 and Al11RE3 whose principle part is Mg17Al12. Certain additive of Ca can promote the heat stability of Mg17Al12 and the elevated temperature tensile strength of the alloy of both cast and heat treatment state. But excessive Ca may promote the alloy ruptures and bring down its elevated temperature tensile strength and plasticity. Under the temperature of 250℃, the way in which the alloy ruptures is mainly brittle. The reasonable staple of the alloy is: Mg(balance)-Al(5.5%)-MM(2.0%)-Ca(1.0%).