The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were in...The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were investigated. The Mg-MM intermediate alloy was prepared by permanent mold casting and then was extruded into the bars. The microstructure and analytical studies were carried out using optical microscopy and differential scanning calorimetry (DSC). Testing results shows the Mg-MM intermediate alloy could melt easily down at die casting temperature of 680 ℃ that was lower than the melting point of lanthanum (918 ℃) and that of cerium (798 ℃). This was propitious to protection the alloy from the oxidation at high temperatures. Then magnesium alloy test bars were produced under conventional cold chamber die casting condition with addition of different weight of the Mg-MM intermediate alloy. Observation and analysis indicated that the microstructures of the alloy were refined and RE containing Al phase was formed with increasing RE addition. The data obtained by tensile tests showed that alloying with mischmetal improved the tensile property of the AZ91D magnesium die casting alloy at ambient temperature.展开更多
In this study,a molten salt co-reduction method was proposed for preparing Y-Al intermediate alloys and the electrochemical co-reduction behaviors of Y(Ⅲ)and Al(Ⅲ)and the reaction mechanism of intermetallic compound...In this study,a molten salt co-reduction method was proposed for preparing Y-Al intermediate alloys and the electrochemical co-reduction behaviors of Y(Ⅲ)and Al(Ⅲ)and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques.The results show that the reduction of Y(Ⅲ)at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons,which is controlled by the mass transfer rate.The diffusion coefficient of Y(Ⅲ)in the fluoride salt at a temperature of 1323 K is 5.0238×10^(-3)cm^(2)/s.Moreover,the thermodynamic properties associated with the formation of Y-Al intermetallic compounds were estimated using a steady-state electrochemical method.Y-Al intermediate alloy containing 92 wt%yttrium was prepared by constant current electrolysis at 1323 K in the LiF-YF_(3)-AIF_(3)-Y_(2)O_(3)(6 wt%)-Al_(2)O_(3)(1 wt%)system at a cathodic current density of 8 A/cm^(2)for 2 h.The Y-Al intermediate alloy is mainly composed ofα-Y2Al and Y phases.The development and application of this innovative technology have solved major technical problems,such as a long production process,high energy consumption,and serious segregation of alloy elements at this stage.展开更多
基金the National Key Technology R&D Program for the 11th Five-Year Plan(2006BAE04B01 ,2006BAE04B04) the National Basic Research Program ("973") of China (2007CB613705)
文摘The preparation techniques of Mg-mischmetal intermediate alloy and the effects of the mischmetal addition ranging from 0.45% to 1.04% on the microstructure and properties of AZ91D alloy prepared by die casting were investigated. The Mg-MM intermediate alloy was prepared by permanent mold casting and then was extruded into the bars. The microstructure and analytical studies were carried out using optical microscopy and differential scanning calorimetry (DSC). Testing results shows the Mg-MM intermediate alloy could melt easily down at die casting temperature of 680 ℃ that was lower than the melting point of lanthanum (918 ℃) and that of cerium (798 ℃). This was propitious to protection the alloy from the oxidation at high temperatures. Then magnesium alloy test bars were produced under conventional cold chamber die casting condition with addition of different weight of the Mg-MM intermediate alloy. Observation and analysis indicated that the microstructures of the alloy were refined and RE containing Al phase was formed with increasing RE addition. The data obtained by tensile tests showed that alloying with mischmetal improved the tensile property of the AZ91D magnesium die casting alloy at ambient temperature.
基金Project supported by the Financial Science and Technology Special Projects of China(XCSTS-TI2020-28)。
文摘In this study,a molten salt co-reduction method was proposed for preparing Y-Al intermediate alloys and the electrochemical co-reduction behaviors of Y(Ⅲ)and Al(Ⅲ)and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques.The results show that the reduction of Y(Ⅲ)at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons,which is controlled by the mass transfer rate.The diffusion coefficient of Y(Ⅲ)in the fluoride salt at a temperature of 1323 K is 5.0238×10^(-3)cm^(2)/s.Moreover,the thermodynamic properties associated with the formation of Y-Al intermetallic compounds were estimated using a steady-state electrochemical method.Y-Al intermediate alloy containing 92 wt%yttrium was prepared by constant current electrolysis at 1323 K in the LiF-YF_(3)-AIF_(3)-Y_(2)O_(3)(6 wt%)-Al_(2)O_(3)(1 wt%)system at a cathodic current density of 8 A/cm^(2)for 2 h.The Y-Al intermediate alloy is mainly composed ofα-Y2Al and Y phases.The development and application of this innovative technology have solved major technical problems,such as a long production process,high energy consumption,and serious segregation of alloy elements at this stage.
