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Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

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International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 136-146页

作者： Chenjin Zhang Guangyu Yang Lei Xiao Zhiyong Kan Jing Guo Qiang Li wanqi jie State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China College of Materials Science and Engineering Fuzhou UniversityFuzhou 350108China College of Chemistry and Environmental Science Qujing Normal UniversityQujing 655011China

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed *** dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)*** the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical-rare-earth(RE)*** alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening *** results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

关键词： Mg-rare earth alloys extrusion temperature extrusion ratio extrusion speed strengthening mechanisms

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Microstructure, Microsegregation, and Mechanical Properties of Directional Solidified Mg–3.0Nd–1.5Gd Alloy

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Acta Metallurgica Sinica(English Letters) 2014年第6期27卷 1134-1143页

作者： Shaojun Liu Guangyu Yang wanqi jie State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The microstructure, microsegregation, and mechanical properties of directional solidified Mg–3.0Nd–1.5Gd ternary alloys were experimentally studied. Experimental results showed that the solidification microstructure was composed of dendrite primary a（Mg） phase and interdendritic a（Mg） · Mg12（Nd, Gd） eutectic and Mg5 Gd phase. The primary dendrite arm spacing k1 and secondary dendrite arm spacing k2 were found to be depended on the cooling rate R in the form k1= 8.0415 9 10-6R-0.279 and k2= 6.8883 9 10-6R-0.205, respectively, under the constant temperature gradient of40 K/mm and in the region of cooling rates from 0.4 to 4 K/s. The concentration profiles of Nd and Gd elements calculated by Scheil model were found to be deviated from the ones measured by EPMA to varying degrees, due to ignorance of the back diffusion of the solutes Nd and Gd within a（Mg） matrix. And microsegregation of Gd depended more on the growth rate, compared with Nd microsegregation. The directionally solidified experimental alloy exhibited higher strength than the non-directionally solidified alloy, and the tensile strength of the directionally solidified experimental alloy was improved,while the corresponding elongation decreased with the increase of growth rate.

关键词： Mg–Nd–Gd ternary magnesium alloy Directional solidification microstructures Dendrite growth Microsegregation Mechanical property

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A Model for Evaluation of Grain Sizes of Aluminum Alloys with Grain Refinement Additions

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Journal of Materials Science & Technology 2007年第5期23卷 619-622页

作者： Zhongwei CHEN Zhi HE wanqi jie State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China

Based on the assumption that the nucleation substrates are activated by constitutional undercooling generated by an adjacent grain growth and solute distribution during the initial solidification, a model for calculation of the grain size of aluminum alloys with the grain refinement is developed, where the nucleation is dominated by two parameters, i.e. growth restriction factor Q and the undercooling parameter P. The growth restriction factor Q is proportional to the initial rate of constitutional undercooling development and can be used directly as a criterion of the grain refinement in the alloys with strong potential nucleation particles. The undercooling parameter P can be regarded as the maximum of constitutional undercooling △Tc. For weak potential nucleation particles, the use of RGS would be more accurate. The experimental data of the grain refinement of pure aluminum and AlSi7 alloys are coincident predicted results with the model.

关键词： Grain refinement Constitutional undercooling Nucleation Aluminum alloys

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The Effect of Magnetic Field on Resistivity of Hg_(0.89)Mn_(0.11)Te in Different Temperature Range

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Journal of Wuhan University of Technology(Materials Science) 2015年第5期30卷 923-927页

作者：王泽温 jie wanqi School of Insurance and Economics University of International Business and Economics Beijing 100029 China Disaster Research Center PICC Property and Casualty Company Limited Beijing 100022 China School of Materials Science and Engineering Northwestern Polytechnical University Xi'an 710072 China

The resistivity of Hg0.89Mn0.11Te has been measured by the superconducting quantum interference device magnetometer in the temperature range from 5 to 200 K under the applied magnetic field of 1, 2, 4 and 6.5 Tesla, respectively, compared with that of no-magnetic field. The results show that the resistivity increases with increase applied magnetic field at higher temperature from 80 to 200 K, but decreases at lower temperature from 5 to 25 K. There exists a transitive range from 25 to 80 K, where the variation of the resistivity shows different tendencies depending on the strength of magnetic field. Maximum difference of resistivity under 6.5 Tesla from that without magnetic field in the temperature range from 30 to 200 K is only about 5 Ω·cm, but it increases up to 3 orders of magnitude at 5 K. The analysis shows that the variation of resistivity of Hg0.89Mn0.11Te under the magnetic field is the algebraic sum of the transverse direction magnetoresistance effect and the sp-d exchange interaction effect. TDRME plays major role in the high temperature range. However, with the decrease of temperature, the effect of sp-d EI on the resistivity gradually exceeds that of the transverse direction magnetoresistance effect through the transitive range, and becomes the dominant effect in the temperature range from 5 to 25 K, which leads to the dramatic decrease of resistivity.

关键词： Hg1-x Mnx Te resistivity magnetoresistance transverse direction magnetoresistance effect sp-d exchange interaction effect

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Magnetic Properties of Diluted Magnetic Semiconductor Hg_(0.89)Mn_(0.11)Te

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Journal of Wuhan University of Technology(Materials Science) 2015年第6期30卷 1130-1133页

作者：王泽温 jie wanqi School of Insurance and Economics University of International Business and Economics Disaster Research Center PICC Property and Casualty Company Limited School of Materials Science and Engineering Northwestern Polytechnical University

The magnetization of Hg0.89Mn0.11 Te single crystal grown by vertical Bridgman method was studied by using superconducting quantum interference device magnetometer（SQUID Magnetometer）. First, magnetization measurements were done under various magnetic fi eld strengths from-20 kOe to 20 kOe at 5 K, 15 K, and 77 K, respectively. Then, the magnetizations were measured with continuous changes of temperature in the range from 5 K to 300 K under the magnetic field of 0.1 kOe and 10 kOe, respectively. The modifi ed Brillouin function was well fitted with the data of magnetization vs. magnetic field strength. The analysis indicated that there was an antiferromagnetic exchange coupling among Mn^2＋ ions. The results of reciprocal susceptibility vs. temperature fi t Curie-Weiss law very well at the temperatures above 40 K, but deviate from the law from 5 Kto 40 K, which shows that the antiferromagnetic exchange coupling among Mn^2＋ ions increases in the lower temperature range below 40 K. The experimental result was explained by extending higher-order terms in the calculation of susceptibility and fitted by a power law function. The measurements reveal that Hg0.89Mn0.11 Te possesses paramagnetic properties at temperatures from 5 K to 300 K.

关键词： diluted magnetic semiconductor Hg1-xMnxTe magnetization

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Structural Stability and Half Metallic Features of Zn_(0.5)Cr_(0.5)S under Pressure

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Journal of Materials Science & Technology 2014年第3期30卷 234-238页

作者： Yuhong Huang wanqi jie Yan Zhou Gangqiang Zha State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University

Spin-polarized first-principle was performed to study the structural stability and the electronic states of Cr doped ZnS with the Cr component of 50% in zincblende （ZB）, wurtzite （W） and rocksalt （RS） structures under pressure. The results show that the zincblende and wurtzite structures become unstable under low pressures of about 4.68 and 9.61 GPa, respectively, but the rocksalt structure can be maintained up to an extremely high pressure of about 32.92 GPa. Both zincblende and wurtzite ***.5S display half metallic features under pressure, while rocksalt *** exhibits metallic feature. The half metallic features can be ascribed to the stronger interactions between S-3p and Cr-3d states and the metallic feature is due to the higher crystal symmetry of rocksalt Zn0.5Cr0.5S. These results can provide helpful guidance for Cr doped ZnS to be used in spintronic devices.

关键词： Structural stability Half metallic features Electronic properties Zn0.5Cr0.5S Pressure

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Effect of mechanical anisotropy on material removal rate and surface quality during polishing CdZnTe wafers

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Rare Metals 2011年第4期30卷 381-386页

作者： LI Yan jie wanqi KANG Renke GAO Hang State Key laboratory of Solidification Processing Northwestern Polytechnical University Xi＇an 710072 China Key Laboratory for Precision and Non-Traditional Machining Technology （Ministry of Education of China） Dalian University of Technology Dalian 116024 China

The mechanical characters of CdZnTe crystal were investigated by nanoscratch tests, and the effects of mechanical anisotropy on the material removal rate and surface quality were studied by polishing tests. There is a peak of frictional coefficient at the early stage of scratch, and increasing the vertical force will result in the increase of peak value correspondingly. The fluctuation phenomenon of frictional coefficient is generated at high vertical force. The lateral forces show the apparent twofold and threefold symmetries on （110） and （111） planes, respectively. To obtain high surface quality, low polishing pressure and hard direction （〈 T10 〉 directions on （110） plane and 〈 112 〉 directions on （111） plane） should be selected, and to achieve high material removal rate, high polishing pressure and soft direction （〈001〉 directions on （110） plane and 〈 121 〉 directions on （111） plane） should be selected.

关键词： cadmium compounds single crystals nanoscratch tests frictional coefficient material removal rate surface quality anisotropy

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Simulation research on control algorithm of differential pressure casting process

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China Foundry 2009年第3期6卷 202-207页

作者： Chai Yan jie wanqi Yang Bo School of Materials Science and Engineering Northwestern Polytechnical UniversityXi''an 710072China School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi''an 710072China The Second Artillery Engineering CollegeXi''an 710025China

To improve the precision of the filling pressure curve of differential pressure casting controlled with PID controller,the model of differential pressure casting process is established and two pressure-difference control systems using PID algorithm and Dahlin algorithm are separately designed in MATLAB. The scheduled pressure curves controlled with PID algorithm and Dahlin algorithm,respectively,are comparatively simulated in MATLAB. The simulated pressure curves obtained show that the control precision with Dahlin algorithm is higher than that with PID algorithm in the differential pressure casting process,and it was further verified by production practice.

关键词： differential pressure casting control algorithm PID Dahlin MATLAB simulation

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Microstructure evolution,mechanical properties and diffusion behaviour of Mg-6Zn-2Gd-0.5Zr alloy during homogenization

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Journal of Materials Science & Technology 2018年第12期34卷 2246-2255页

作者： Lei Xiao Guangyu Yang Yang Liu Shifeng Luo wanqi jie State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The microstructure evolution and mechanical properties of Mg-6 Zn-2 Gd-0.5 Zr alloy during homogenization treatment were investigated. The as-cast alloy was found to be composed of dendritic primaryα-Mg matrix, α-Mg +W（Mg;Zn;Gd;） eutectic along grain boundaries, and icosahedral quasicrystalline I（Mg;Zn;Gd） phase within α-Mg matrix. During homogenization process, α-Mg +W（Mg;Zn;Gd;） eutectic and I phase gradually dissolved into a-Mg matrix, while some rod-like rare earth hydrides（GdH2）formed within α-Mg matrix. Both the tensile yield strength and the elongation showed a similar tendency as a function of homogenization temperature and holding time. The optimized homogenization parameter was determined to be 505℃ for 16 h according to the microstructure evolution. Furthermore,the diffusion kinetics equation of the solute elements derived from the Gauss model was established to predict the segregation ratio of Gd element as a function of holding time, which was proved to be effective to evaluate the homogenization effect of the experimental alloy.

关键词： Mg alloy Homogenization Segregation Diffusion kinetics

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ZnCl_2-assisted Synthesis of ZnSe Polycrystal

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Journal of Materials Science & Technology 2012年第4期28卷 373-378页

作者： Changyou Liu Tao Wang Gangqiang Zha Zhi Gu wanqi jie State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China

A chemical-assisted element direct-reaction method is developed to synthesize ZnSe compound semiconductor material at a relatively low temperature （-1000 ℃）. ZnSe polycrystal was obtained in the closed-tube systems with Zn-Se, Zn-Se-Zn（NHa）2CI2, ZnoSe-NH4CI and Zn-Se-ZnCI2. The as-synthesized samples were tested by X-ray diffraction （XRD）, thermogravimetric analysis （TGA） and analyzed by thermodynamic numerical method. The results demonstrate that the synthesis efficiency is higher than 99.96% for Zn-Se-ZnCl2 system at around 1000 ℃ for 3 weeks. It also exhibits that not only temperature, but also low apparent ratio of volume and surface area of the source materials and higher ZnCl2 content are required to achieve high synthesis efficiency. A SeCI transporting reaction synthesis process is proposed based on the thermodynamic analysis.

关键词： Crystallites Growth from vapor Zinc compounds Semiconducting II-VI materials

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