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Acta Metallurgica Sinica(English Letters) 2017年第9期30卷 895-906页

作者： Rui-Yang Liang Ping Yang wei-min mao School of Materials Science and Engineering University ofScience and Technology BeijingBeijing 100083China

In this study, high- and low-grade grain-oriented electrical steels were used as the initial materials to produce 0.08-mm-thick sheet with one-step cold-rolling method. Electron backscattering diffraction analysis technique and X-ray diffraction texture analysis technique were adopted to investigate the effect of initial Goss texture sharpness on texture evolution and magnetic properties of ultra-thin grain-oriented electrical steel. The results showed that primary recrystal- lization and secondary recrystallization were the main processes that occurred during annealing. The induced factors for secondary recrystallization of two grades samples were not Consistent. The high-grade samples presented texture induction mechanism, while the low-grade samples revealed strong surface-energy induction mechanism. The initial Goss texture sharpness had a great impact on texture evolution and magnetic properties of ultra-thin grain-oriented electrical steel. The Goss texture component formed after primary recrystallization was stronger, and better magnetic properties were obtained at low frequencies. For low-grade samples, secondary recrystallization enhanced the intensity of Goss texture, and both grain size and texture contributed to better high-frequency magnetic properties after secondary recrystallization. By controlling the annealing process, the magnetic properties of low-grade products could be significantly improved, thus achieving conversion from low-grade to high-grade products.

关键词： Ultra-thin grain-oriented electrical steel Goss texture Secondary recrystallization Magnetic properties

Effect of heat treatment on the microstructure and micromechanical properties of the rapidly solidified Mg61.7Zn34Gd4.3 alloy containing icosahedral phase

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International Journal of minerals,Metallurgy and Materials 2019年第7期26卷 869-877页

作者： Wen-bo Luo Zhi-yong Xue wei-min mao School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Institute for Advanced Materials North China Electric Power University Beijing 102206 China School of Energy Power and Mechanical Engineering North China Electric Power University Beijing 102206 China

In this paper, the microstructure evolution of the rapidly solidified (RS) Mg61.7Zn34Gd4.3 (at%, atomic ratio) alloy at high temperatures was investigated. The hardness and elastic modulus of the main precipitated phases were also analyzed and compared with those of the α-Mg matrix on the basis of nanoindentation tests. The results show that the RS alloy consists of either a petal-like icosahedral quasicrystal (IQC) phase (~20 μm) and block-shaped H1 phase (~15 μm) or IQC particles with an average grain size of ~107 nm as well as a small proportion of amorphous phase, which mainly depends on the holding time at the liquid temperature and the thickness of the ribbons. The IQC phase gradually transforms at 400?C to a short-rod-shaped μ-phase (Mg28.6Zn63.8Gd7.7) with a hexagonal structure. The hardness of the IQC phase is higher than that of H1 phase, and both phases exhibit a higher hardness than the α-Mg matrix and the μ-phase. The elasticity of the H1 phase is superior to that of the α-Mg matrix. The IQC phase possesses a higher elastic modulus than H1 phase. The easily formed H1 phase exhibits the poorest plastic deformation capacity among these phases but a higher elastic modulus than the α-Mg matrix.

关键词： magnesium alloy icosahedral phase rapidly solidification nanoindentation micromechanical properties

Semisolid A356 alloy feedstock poured through a serpentine channel

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International Journal of minerals,Metallurgy and Materials 2009年第5期16卷 603-607页

作者： Xiao-rong Yang wei-min mao Chong Gao School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China School of Materials Science and Engineering Taiyuan University of Science and Technology Taiyuan 030024 China

Fine spheroidal and equiaxed nondendritic microstructures required for semisolid casting can be formed through a serpentine pouting channel. Effects of the pouring temperature and the vertical section length of the serpentine pouring channel were studied. The results indicate that both favorable semisolid microstructures of A356 aluminum alloy can be generated by a serpentine pouring channel, and the solid shell inside the channel can be avoided when the pouting temperature is in the range from 660 to 680℃. It is also shown that the vertical section length of the serpentine pouting channel has a significant influence on the microstructure of the feedstock, namely both the microstructure of the feedstock and the microstructure uniformity in the radial direction get worse when the vertical section length is shortened; moreover, the pouring temperature for obtaining the feedstock with suitable microstructure decreases. The relevant mechanisms were discussed.

关键词： semisolid microstructure serpentine channel primary α-A1

Preparation of semi-solid aluminum alloy slurry poured through a water-cooled serpentine channel

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International Journal of minerals,Metallurgy and Materials 2012年第1期19卷 48-53页

作者： Zheng-zhou Chen wei-min mao Zong-chuang Wu School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

A water-cooled serpentine channel pouring process was invented to produce semi-solid A356 aluminum alloy slurry for rheocast ing, and the effects of pouring temperature and circulating cooling water flux on the microstmcture of the slurry were investigated. The results show that at the pouring temperature of 640-680~C and the circulating cooling water flux of 0.9 m3/h, the semi-solid A356 aluminum alloy slurry with spherical primary a（A1） grains can be obtained, whose shape factors are between 0.78 and 0.86 and the grain diameter can reach 48-68 ~am. When the pouring temperatures are at 660-680~C, only a very thin solidified shell remains inside the serpentine channel and can be removed easily. When the serpentine channel is cooled with circulating water, the microstructure of the semi-solid slurry can be improved, and the serpentine channel is quickly cooled to room temperature after the completion of one pouring. In terms of the productivity of the special equipment, the water-cooled serpentine channel is economical and efficient.

关键词： semi-solid slurry aluminum alloys microstructure rheocasting

Tensile properties and microstructure of rheo-diecast 7075 alloy prepared by serpentine channel process

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China Foundry 2019年第3期16卷 161-167页

作者： wei-min mao Wen-zhi Zhu School of Materials Science and Engineering University of Science & Technology Beijing Beijing 100083 China State Key Laboratory of Materials Processing and Die & Mould Technology Huazhong University of Science & Technology Wuhan 430074 China

A semisolid slurry of 7075 aluminum alloy was prepared by means of a serpentine channel process (SCP) and rheo-diecasting. The influences of pouring temperature during slurry preparation, the injection pressure and die preheat temperature on the mechanical properties and microstructure of a rheo-diecast 7075 aluminum alloy were investigated. The results show that the as-cast strength and elongation of the tensile samples were 210-260 MPa and 0.2%-1.7%, respectively, with an injection pressure of 130 MPa, a pouring temperature of 700-720℃, a preheat temperature of 280-350℃, and a plunger speed of 0.5 m·S^-1. The results also show that the aged strength and elongation of the tensile samples were 420-453 MPa and 1.0%-1.4%, respectively, when the alloy solution was treated at 470℃ for 12 h and aged at 120℃ for 24 h. The substantial shrinkage porosity in the 7075 aluminum alloy tensile samples was the main cause of low elongation.

关键词： serpentine channel rheo-die casting 7075 aluminum alloy microstructure tensile properties

Different Mechanisms of ε-M and α'-M Variant Selection and the Influencing Factors of ε-M Reversion During Dynamic Tension in TRIP Steel

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Acta Metallurgica Sinica(English Letters) 2018年第5期31卷 449-455页

作者： Li-Na Wang Ping Yang Ting Jin wei-min mao School of Materials Science and Engineering University of Science and Technology Beijing Department of Materials School of Tianjin University of Science and Technology Beijing

The variant selection of martensites（ε-M and α＇-M） and ε-M reversion in dynamic tensile high-manganese TRIP steel were investigated. α＇-M variant pairs with a zigzag morphology frequently formed, and the pairs of neighboring α＇-M variants were examined in terms of mechanical work and strain energy reduction. The occurrence of a primary α＇-M variant is determined by mechanical work, but high products of mechanical work and strain energy reduction are essential for secondary variant selection. In contrast to α＇-M variant pair selection, ε-M variant selection can be attributed to the highest mechanical work. During ε-M→α＇-M transformation, the mechanical work of ε-M reversion is higher than that of α＇-M variant, thereby implying that ε-M reversion in h110 icgrain is possible. e-M plate distribution also affects the feasibility of ε-M reversion.

关键词： TRIP-assisted steel Dynamic plastic deformation Martensitic transformation Variantselection Orientation relationship

Orientation gradient on surface of non-oriented electrical steel annealed by γ → α transformation

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Journal of Iron and Steel Research(International) 2020年第1期27卷 88-95页

作者： Jin-hua Wang Ping Yang wei-min mao Feng-e Cui School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

The microstructures and textures of the non-oriented electrical steel sheets under various annealing conditions were investigated.The orientation gradient in the interior of grains appeared on the surface of steel sheets after α→γ→α transformation in various atmospheres.The orientation gradient that appeared on the surface was inherited into the center of the steel sheet in H2 atmosphere,while that appeared only in the grains of the surface layer during γ→α transformation with N2 atmosphere.The thin oxide scale was generated in various atmospheres containing traces of O2 and H2O.The formation mechanism of orientation gradient is related to the thermal stress caused by the difference of thermal expansion coefficients between the oxide scale and the thin ferrite on the surface.The combined effect of phase transformation stress and thermal stress caused the plastic deformation of the thin ferrite grains on the surface in the initial stage of γ→α transformation,and then the orientations of the thin ferrite grains gradually rotated and caused the orientation gradient in the interior of grains.

关键词： Electrical steel Texture Phase transformation-Thermal stress Oxide scale

Punchability and Punching Fracture Behavior of High Silicon Steel Sheets

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Journal of Iron and Steel Research(International) 2015年第9期22卷 852-857页

作者： Jing QIN Ping YANG wei-min mao Feng YE School of Materials Science and Engineering University of Science and Technology Beijing State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The 0.2-0.3mm thick cold-rolled sheets and annealed sheets of high silicon steel were produced by rolling process,then punching tests were carried out at room temperature to 150℃.The punchability and punching fracture behavior were investigated by means of scanning electron microscope（SEM）and electron back-scattered diffraction（EBSD）.It is found that cold-rolled sheets of high silicon steel show good punchability under the condition of 0.01 mm punch-die clearance and at the temperature of 100℃;the punchability of annealed sheets with fine grain size is better than that of annealed sheets with coarse grain size;the punching temperature of 150℃is suitable for annealed high silicon steel sheets especially with coarse grain size on account of punching edge quality.The major cleavage planes of annealed high silicon steel sheets are{100}crystallographic planes on which brittle fracture occurs at low temperatures.The cleavage systems include{100}〈110〉and{100}〈100〉,and cleavage fracture is completed by one or both of them.The punchability of high silicon steel sheets is related with punching temperature,grain size and ordering degree.Reducing ordering degree,increasing punching temperature,as well as refining grain size can improve the ductility and punchability of high silicon steel sheets.

关键词： high silicon steel punch-die clearance punchability cleavage fracture dimple fracture

Correlation between Primary and Secondary Recrystallization Texture Components in Low-temperature Reheated Grain-oriented Silicon Steel

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Journal of Iron and Steel Research(International) 2016年第11期23卷 1234-1242页

作者： Gong-tao LIU Zhi-qiao LIU Ping YANG wei-min mao School of Materials Science and Engineering University of Science and Technology Beijing

Low-temperature slab-reheated grain-oriented silicon steel is characterized by a sharp {411}〈148〉 primary recrystallization texture. To date, the influence of this texture on secondary recrystallization is not clear. Microtextures in primary and secondary reerystallized sheets of low-temperature reheated grain-oriented silicon steel were examined using electron backscatter diffraction. By comparing the textures and microstructures of specific primary reerystallized grains neighboring secondary grains with those of other primary grains, the influences of primary re- crystallization textures and microstructures on the orientations of secondary grains were investigated. Results show that for low-temperature reheated graiworiented silicon steel, the primary recrystallization sheet comprises { 411 } 〈148〉, {111}〈112〉, and {001}〈120〉 texture componems. During secondary recrystallization, the {111}〈112〉 primary recrystallized grains were easily consumed by abnormally grown Goss, deviated Goss, Brass, or {210}〈001〉grains ;the { 411 }〈148〉 primary recrystallized grains were more resistant to being swallowed; and the {001} 〈120 grains were the most resistant to being consumed. For a particular primary grain, the distribution of its surrounding grain boundaries determined how easily it is consumed during secondary recrystallization. Primary grains surrounded by 20°- 45° grain boundaries were consumed much earlier than those having grain boundaries above 45°, which is in accordance with high-energy grain boundary theory. In addition, special ∑9 boundaries between {411}〈148〉 and Goss grains move more slowly than ∑9 boundaries between {111 }〈112〉 and Goss grains, which is attributed to the different positions of 〈110〉 rotation axis with respect to the normals of grain boundaries.

关键词： grain-oriented silicon steel secondary recrystallization texture low-temperature slab reheating

Numerical simulation on reho-diecasting mould filling of an automobile master brake cylinder

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International Journal of minerals,Metallurgy and Materials 2009年第2期16卷 184-188页

作者： Yue-long Bai wei-min mao Hong Xu Jun Xu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China General Research Institute for Non-ferrous Metals Beijing 100088 China Research Center for Foundry Engineer North University of China Taiyuan 030051 China

An apparent viscosity model of semi-solid A356 aluminum alloy has been developed and the software Castsofl6.0 coupled with the model has been used to simulate the mould filling of an automobile master brake cylinder with the semi-solid A356 aluminum alloy slurry. The simulation results are in agreement with the practical filling process, indicating that the apparent viscosity model is feasible and can be used to simulate the mould filling of the semisolid A356 aluminum alloy slurry and can be used to optimize the filling process and the design of dies. A higher injection pressure, a higher ingate flow velocity of the semi-solid slurry, and a higher slurry temperature are advantageous to the mould filling of the automobile master brake cylinder.

关键词： semi-solid A356 aluminum alloy reho-diecasting numerical simulation