用改进的CSA法计算多元固溶体混合熵

CSA法在估算多元固溶体的混合料,骨比CVM法计算简单的优点,所以,CSA法特别适合于利用实验数据优化计算多元合金体系的相图,采用相同的能量参数及结构,比较了用蒙特卡罗（MC）法、CVM法及CSA法计算的结果,由此可知,由于CSA法引入了1个参数,增强了实用性,计算得到的Cu-Au相图与用蒙特卡罗（MC）法及CMV法计算的结果一致。     

Effect of solidification condition on secondary dendrite arm spacing of the A357 alloy under counter-pressure casting

The effect of counter-pressure casting parameters on secondary dendrite arm spacing (SDAS) of A357 alloy under different process parameters was studied. Quartz sand mould with chill can strongly decrease the SDAS. Reduced SDAS close to the mould bottom because of chilling was obtained. Pressure seems to have no apparent effect on the SDAS. In order to obtain casts with UTS ⩾ 320 MPa, SDAS must be less than 55 μm, which means a local cooling rate V _L⩾0.23 °C/s. Funded by the Innovation Fund for Outstanding Scholar of Henan Province(No. 0621000700)     

热型连铸过程的二维稳态传热模型

根据热型连铸技术原理,建立了热型连铸凝固过程二维稳态温度场的物理、数学模型.通过数值计算,得出了铸型出口温度、冷却距离、拉铸速度和喷水冷却强度等工艺参数对铸坯固液界面位置的影响.计算结果与文献报道的实验结果吻合较好.     

AZ31B合金的铸轧组织

利用金相及扫描电镜对AZ31B合金热模拟和铸轧样组织结构进行研究。研究结果表明：在不同应变量下,热模拟样品的晶粒粒度均随应变速率的增加而减小,而当其他条件相同时,变形量越大晶粒粒度越小,冷却强度降低,合金呈典型铸态组织;利用铸轧技术生产的AZ31B合金,当应变速率一定时,随着初始铸轧温度的降低,铸轧态板材的树枝晶粒度逐渐减小;而在初始铸轧温度一定时,随着应变速率的增大,铸轧态合金板材的树枝晶粒度也逐渐减小;而随着应变速率的提高,树枝晶沿轧向呈流线状排列的趋势增强;在AZ31B合金铸轧过程中,轧制力不能太大,否则容易引起热裂。     

Application of the gel casting process in iron powder metallurgy

The effects of various gel casting process parameters such as the dispersant and solid loading on the rheology of Fe slurries, molding, and sintering behaviors were studied. The relationship between solid loading and viscidity in the process of iron base powder metallurgy was researched to obtain better microstructure and properties. The results showed that the viscosity of Fe slurries is obviously reduced with the increase of the dispersant. The suitable parameters are as follows： the solid loading is 61% and sintering temperature is 1180℃. Iron parts with relatively high density and better properties were obtained by the gel casting process.     

Effects of correlative factors on the interdendritic melt flow brought by the bulge in continuous casting slabs

The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.     

Mechanism of Flowing Stop of Al-Si Alloys in EPC Process

ＭｅｃｈａｎｉｓｍｏｆＦｌｏｗｉｎｇＳｔｏｐｏｆＡｌ－ＳｉＡｌｌｏｙｓｉｎＥＰＣＰｒｏｃｅｓｓＷＥＩＺｕｎｊｉｅ；ＡＮＧｅｙｉｎｇ（魏尊杰，安阁英）（ＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅ．ａｎｄＥｎｇｉｎｅｅｒｉｎｇ，Ｈａｒｂｉｎｉｎｓｔ...     

Nb微合金化钢异型坯连铸工艺的优化

为了减少Nb微合金化钢连铸异型坯表面裂纹缺陷,研究了Nb微合金化钢的高温塑性,并结合工业性试验,对Nb微合金化钢异型坯连铸二冷工艺制度进行了优化;另外对结晶器用保护渣的理化性能进行了改进,大大提高了Nb微合金化钢连铸异型坯表面质量。     

Numerical Simulation of Al-Si Alloys Filling in EPC Processes

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆＡｌ－ＳｉＡｌｌｏｙｓＦｉｌｌｉｎｇｉｎＥＰＣＰｒｏｃｅｓｓｅｓＷＥＩＺｕｎＪｉｅ；ＡＮＧｅｙｉｎｇ；ＣＨＡＮＧＱｉｎｇｍｉｎｇ魏尊杰，安阁英，常庆明（Ｄｅｐｔ．ｏｆＭａｔｅｒｉａｌＥｎｇｉｎｅｅｒｉｎｇ，Ｈ...     

Rheological behavior of continuous roll casting process of aluminum alloy

The rheological behavior of aluminum alloy and its influencing factors in physical simulation of continuous roll casting process were studied by using a Gleeble-1500 thermal-mechanical simulation tester with a set of special clamp system. The relationships between the flow stress and the strain rate in the deformation process of simulating roll casting experiment were obtained. The results show that four different characteristic stages exist in the temperature range of the whole rheological process. The first occurs when the temperature is higher than 600℃, which belongs to the creep deformation stage; the second occurs when the temperature lies in the range of 500 - 600℃, and it can be regarded as the high temperature and low stress level deformation stage; the third occurs when the temperature decreases to the range of 300 - 500℃, it is considered to be the middle stress level deformation stage; the last occurs when the temperature is less than 300℃ and the strain rate is less than 1.00 s^-1 , it belongs to middle stress level deformation stage. But when the strain rate is larger than 1.00 s^-1, it belongs to the high stress level deformation stage. And the relative constitutive models suitable for the four different stages of continuous roll casting process were established through multivariate linear regression analysis of the experimental data.     

铸钢件用水基SG-ZGY型复合涂料的研究

采用棕刚玉和锆英粉作耐火材料,研制了铸钢件用水基复合涂料．复合烧结试验及流变特性分析表明：该涂料具有耐高温及良好的触变性、流平性,所生产的铸钢件表面清洁、光滑,不粘砂,易清理．     

Simulation of the continuous casting process in a mold of free-cutting steel 38MnVS based on a MiLE method

A new method called mixed Lagrangian and Eulerian(MiLE)method was used to simulate the continuous casting process in a mold of free-cutting steel 38MnVS.The simulation results are basically in agreement with experimental data in the literature,achieving the three-dimensional visualization of temperature distribution,melt flow,shell thickness,and stress distribution of blooms in a mold.It is shown that the flow velocity of steel melt becomes smaller gradually as the casting proceeds.When the flow reaches a certain depth,two types of flow patterns can be observed in the upper zone of the mold.The first flow pattern is to flow downwards,and the second one is to flow upwards to the meniscus.The comer temperature is higher,and the thickness is thinner than those in the mid-face.The effective stress in the comer area is much bigger than that in the mid-face,indicating that the comer area is the dangerous zone of cracking.     

铝合金框架压铸工艺数值模拟及分析

通过应用多种软件交换和数据接口技术,设计了正交实验以完成压铸过程数值模拟。结果表明：通过设置合理浇注系统、控制压铸速度和提高模具预热温度,可以有效减少铸件缩松缩孔;各参数对铸件缩松缩孔发生概率影响程度从大到小依次为浇注系统方式、模具预热温度、压铸速度;理想工艺方案为浇注系统a、压铸速度1 m/s、模具预热温度450℃。     

Evaluation of the mold-filling ability of alloy melt in squeeze casting

The mold-filling ability of alloy melt in squeeze casting process was evaluated by means of the maximum length of Archimedes spiral line. A theoretical evaluating model to predict the maximum filling length was built based on the flowing theory of the incompressible viscous fluid. It was proved by experiments and calculations that the mold-filling pressure and velocity are prominent influencing factors on the mold-filling ability of alloy melt. The mold-filling ability increases with the increase of the mold-filling pressure and the decrease of the proper mold-filling velocity. Moreover, the pouring temperature relatively has less effect on the mold-filling ability under the experimental conditions. The maximum deviation of theoretical calculating values with experimental results is less than 15％. The model can quantitatively estimate the effect of every factor on the mold-filling ability.     

挤压铸造ZA27合金的力学性能及摩擦磨损性能

研究了挤压铸造对ZA27合金力学性能的影响,挤压铸造可以显著地提高ZA27合金的常温力学性能和高温力学性能.随着比压的增加,其综合力学性能提高.比压为750 MPa时,与金属型重力铸造合金相比,抗拉强度提高了约19.2%,硬度提高了约25.5%,伸长率增加了12.3%.采用MM-W1立式万能摩擦磨损试验机研究了比压对ZA27合金的摩擦磨损性能的影响,结果表明,在转速为200 r/min,载荷为100 N,摩擦副为45钢,20号机油润滑条件下,挤压比压为750 MPa时,合金的摩擦磨损性能较好.     

Water modeling of mold powder entrapment in slab continuous casting mold

The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the shearing flow near the narrow face of mold, the entrapment caused by vortexes around the submerged entry nozzle (SEN), and the entrapment caused by the Ar bubbling. Both the velocity of the surface flow and the level fluctuation of the liquids are enlarged with increasing the casting speed, reducing the submersion depth of SEN, decreasing the downward angles of the nozzle outlets, and increasing the Ar flowrate, all of which in- crease the tendency of mold powder entrapment. Among the four above-mentioned factors, casting speed has the largest effect.     

Kinetics of recrystallization for twin-roll casting AZ31 magnesium alloy during homogenization

The kinetics of recrystallization for twin-roll casting AZ31 magnesium alloy with different thicknesses during homogenization was analyzed.It is shown that fine grains are first formed at the boundaries of deformed bands in the twin-roll casting slab.The recrystallized grains with no strain are gradually substituted for the deformed microstructure of twin-roll casting AZ31 magnesium alloy.The incubation temperature and time for the recrystallization of a twin-roll casting AZ31 magnesium alloy strip with a thickness of 3 mm are lower and shorter than those of the 6-mm thick strip,respectively.The 3-mm thick twin-roll casting magnesium alloy has finer grains than the 6-mm thick strip.The activation energies of recrystallization for twin-roll casting AZ31 magnesium alloy slabs with the thickness of 3 and 6 mm are 88 and 69 kJ/mol,respectively.The kinetics curves of recrystallization for twin-roll casting AZ31 magnesium alloy were obtained.     

Al-Si合金(A357)重力铸造充型及凝固过程模拟

利用多通道数据采集系统对铸件特定部位的温度进行测量,以掌握该点的凝固和补缩,并利用O lym pu s金相显微镜观察铸件关键部位的宏观组织,进而分析其凝固方式.用商业化模拟软件Z-C ast对铝合金拉伸试棒充型及凝固过程进行模拟,对实际浇注实验中测试点的温度场进行模拟,并将模拟结果与实验结果进行比较.结果表明,当金属铸型的预热温度较低时,必须采用较高的浇注温度才能够使铸型充满,试棒在凝固过程能够得到有效补缩,从而消除了由于糊状凝固造成的显微缩松.铸造模拟软件Z-CA ST能够准确的模拟铝合金铸件充型凝固过程,提供较准确的流场、温度场信息,预测缺陷及其出现位置.     

挤压铸造对ZA27合金组织及性能的影响

研究了挤压铸造对ZA27合金组织及性能的影响.挤压铸造可以显著提高合金的综合力学性能，抗拉强度指标提高了约19.2%，硬度指标提高了约25.5%，延伸率比重力铸造合金增加了近2倍.挤压铸造使合金的组织细化，并使组织中共晶体的数量明显增多，尺寸减小.共晶体由粗大的长条状变成细小的层片状，ε相由棒状或块状变成细小的点状弥散分布于枝晶间.电子探针分析表明，挤压铸造明显改善了合金元素的显微偏析，使试件整体成份均匀.     

Thermal-stress simulation of direct-chill casting of AZ31 magnesium alloy billets

Two-dimensional (2D) transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill (DC) casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters (at pouring temperature of 680 °C, casting speed of 2 mm/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m²·°C⁻¹). The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets. Funded by the 973 National Grand Theoretical Research Program(No. 2007CB613700), the National Sci&Tech Support Program(No. 2007BAG06B04), National Natural Science Foundation of China (No. 50725413), and the Natural Science Foundation of Chongqing(No. CST, 2007bb4413)