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Effect of Initial Goss Texture Sharpness on Texture Evolution and Magnetic Properties of Ultra-thin Grain-oriented Electrical Steel

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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

Preparation of semisolid AlSi7Mg alloy slurry through weak traveling-wave electromagnetic stirring

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International Journal of minerals,Metallurgy and Materials 2009年第5期16卷 554-558页

作者： Zhen-duo Zhao wei-min mao Sha Li Rong-mao Zhong School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The semisolid AlSi7Mg alloy slurry with large capacity was prepared by low superheat pouring and week traveling-wave electromagnetic stirring. The effects of electromagnetic stirring power and frequency on the shape and distribution of primary α-A1 grains in the AlSi7Mg alloy slurry were discussed. The experimental results show that the AlSi7Mg alloy slurry with fine and spherical primary α-A1 grains distributed homogeneously can be obtained. Under the condition of low superheat pouring and week traveling-wave electromagnetic stirring, when the pouring temperature is 630℃, raising the stirring power or frequency appropriately can gain a better shape of primary α-Al grains; but if the stirring power or frequency is increased to a certain value （1.72 kW or10 Hz）, the shape of primary α-A1 grains cannot be obviously improved and spherical primary α-Al grains distributed homogeneously can be still obtained.

关键词： semisolid AlSi7Mg alloy slurry electromagnetic stirring primary a-A1

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 oC,a preheat temperature of 280-350 oC,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 oC for 12 h and aged at 120 oC 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 *** orientation gradient in the interior of grains appeared on the surface of steel sheets after α→γ→α transformation in various *** 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 *** thin oxide scale was generated in various atmospheres containing traces of O2 and *** 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 *** 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

Possible influence of sulfur content on magnetic aging behaviors of non-oriented electrical steels

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Frontiers of Materials Science 2013年第4期7卷 413-416页

作者： wei-min mao Ping YANG Chang-Rong LI Department of Materials State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

Six non-oriented steel sheets of similar grade produced by different steel companies were used to analyze the magnetic aging behaviors after aging at 200~C for 48 h. It was observed that tiny S atoms, besides C and N, could also induce certain increase of core loss during aging. Thermodynamic calculation indicated that the nucleation driving force of FeS is much higher than those of Fe3C and Fe4N at low temperature, while S atoms, which tend to segregated around dislocations and boundaries, would diffuse rapidly along the crystalline defects while FeS particles would form. Therefore, higher content of tiny S atoms could increase core loss during service time of non-oriented steel sheets.

关键词： non-oriented electrical steel sulfur diffusion magnetic aging core loss