Hua HOU
,
Dong-Ying Ju
,
Yuhong ZHAO
,
Jun CHENG
材料科学技术（英文）
Two-dimensional numerical simulation for the dendrite growth of binary alloy during solidification is carried out by a phase field method. In the model equations, phase field, temperature and solute redistribution are all involved. The equations are solved using the finite difference method (FDM) with two different space steps of phase field and temperature field. In calculation, the thermal noise is introduced to generate the side branches; the dependence of dendrite growth on the space step was also investigated. It is shown that thermal noise can trigger the growth of side-branches, however it has no influence on the stable behavior of the dendrite tip; the feature of dendrite growth is reasonable with δ Δx≤0.6W0, Δx is the space step and W0 is the thickness of interface.
关键词:
Phase field
,
null
,
null
Lin HU
,
Xiaodong HU
,
Peng GAO
,
Hongyang ZHAO
,
Dong-Ying Ju
材料科学技术（英文）
Based on the discussing of the mechanisms of grain refinement strengthening and deformation induced transformation, the characteristics of controlled rolling and controlled cooling for high-speed wire were analyzed. Aiming at the problems of wire mill in Anshan Iron & Steel Co., turbulent cooler and spray cooler on the Stelmor conveyor were developed. Super-steels had been developed for Q235 steel through unrecrystallized austenite region rolling. The constitution and properties of the wire on the coil overlap zone were also improved. This proved the possibility that super-steels can be developed in high-speed wire mill.
关键词:
Super-steel
,
null
,
null
,
null
Ming QIN
,
Dong-Ying Ju
,
Yan ZHANG
,
Pei BIAN
材料科学技术（英文）
The previous work has indicated that the carburizing-quenching process is often accompanied by the decarburization in the surficial layer of mechanical parts. A numerical model based on “metallo-thermo-mechanics” was used to estimate the microstructure and residual stresses in the case layer of a carburizing-quenched SCr420 steel. In order to verify above model, the experimental methods, such as XRD, color metallography, microhardness indentation, and EPMA, are also used to analyze the correlative parameters. The decarburization in the carburizing-quenched SCr420 steel was observed, and the simulation results are a little different from the experimental results. According to the results, the factors of reducing the accuracy of the numerical simulation method have been discussed.
关键词:
Decarburization
,
null
,
null
P.Bian
,
Dong-Ying Ju
材料科学技术（英文）
Magnetite (Fe3O4) of ferrite magnetic materials has attracted attentions arising by the chip coil electronic material. However, its industrial applications have been limited by the need of high temperature sintering under reduced pressure or vacuum. In order to develop the process method of low-cost and energy saving with high strength and high magnetism of the magnet, a new low temperature sintering method during CO2 gas and adding small amount of boric acid (H3BO3) are proposed. Here, the superfine magnetite powder was fabricated by decomposition from ferrous oxalate at 500℃ in CO2 gas. The ferrous oxalate was synthesized using iron chloride and ammonium oxalate with the liquid phase precipitation. The magnetite powder compact was produced by Newton press and CIP (cold isostatic press) after adding small amount of boric acid. In this study, the effects of the additive on the mechanical and magnetic properties of the sintered magnet were also evaluated. By characteristic evaluation of the magnet, the validity of the proposed new low-temperature sintering process and the optimal process conditions were confirmed.
关键词:
Ferrite magnet
,
null
,
null
,
null
Hongyang ZHAO
,
Dong-Ying Ju
,
Lin HU
材料科学技术（英文）
The twin-roll casting (TC) process of Al alloy was presented. Microstructure and crystallization of the as-cast strip are investigated to link the strip quality and microstructure with the process conditions. The process variables of cooling rate, temperature history and solidification finish point and their influences are discussed. The results revealed the ability of the twin-roll caster to produce directly the thin strip of Al alloy with improved mechanical strength.
关键词:
Twin-roll
,
null
,
null
,
null
Physical Review B
In a recent publication [S. Dong et al., Phys. Rev. Lett. 103, 127201 (2009)], two (related) mechanisms were proposed to understand the intrinsic exchange bias present in oxides heterostructures involving G-type antiferromagnetic perovskites. The first mechanism is driven by the Dzyaloshinskii-Moriya interaction, which is a spin-orbit coupling effect. The second is induced by the ferroelectric polarization, and it is only active in heterostructures involving multiferroics. Using the SrRuO(3)/SrMnO(3) superlattice as a model system, density-functional calculations are here performed to verify the two proposals. This proof-of-principle calculation provides convincing evidence that qualitatively supports both proposals.
关键词:
thin-films;weak ferromagnetism;superlattices;anisotropy;bifeo3;srruo3;model
赵欣
,
李继定
,
陈剑
,
陈翠仙
膜科学与技术
doi:10.3969/j.issn.1007-8924.2003.06.003
在膜分离过程中,渗透物分子在聚合物膜内的扩散过程,是影响聚合物膜分离性能的关键因素.详细考察了目前被广泛使用的Vrentas-Duda扩散模型,对其进行改进,提出了新的计算ζ的公式.根据新提出的公式,对聚苯乙烯/甲苯(PS/toluene)、聚苯乙烯/乙苯(PS/ethylbenzene)、聚乙酸乙烯酯/甲苯(PVAc/toluene)3种体系中弱极性渗透物分子的扩散系数进行了预测,其较之原Vrentas-Duda扩散模型、Ju改进的Vrentas-Duda扩散模型有更好的预测结果.
关键词:
自由体积
,
扩散模型
,
聚合物膜
,
扩散系数
陈康
,
许希武
,
马凯
材料科学与工程学报
基于Ju和Chen提出的颗粒增强复合材料的一般细观力学方法,采用Qu给出的一阶近似修正的Eshelby张量,本文建立了考虑夹杂之间相互影响的含任意分布弱界面颗粒增强多相复合材料等效模量预测的一般细观力学方法,通过体积均匀化方法得到了一组细观力学本构方程.分别推导了忽略夹杂之间相互影响的弱界面多相复合材料宏观模量表达式以及考虑夹杂之间相互影响的弱界面两相复合材料的宏观模量表达式.此外,还给出了几种特殊复合材料体系在考虑界面弱化下的宏观等效性能参数的解析表达式,在界面粘结完好的假设下,给出的表达式均可以退化成经典的细观力学预测结果.在考虑夹杂之间相互影响的情况下,本文预测结果与实验数据吻合很好,验证了模型的有效性.
关键词:
夹杂之间相互影响
,
轻微弱化界面
,
细观力学
,
等效性能参数
,
颗粒增强复合材料
