Two-dimensional simulation on the rolling process of semi-solid 60Si2Mn by finite element method

The effect of various process variables on the law of metal flow for semi-solid rolling 60Si2Mn was studied by finite element method. Semi-solid 60Si2Mn can be described as compressible rigid visco-plastic porous material saturated with liquid. In terms of ther-mo-mechanical coupling condition, the distributions of stress, velocity and temperature were studied using software MARC. The simulation results show that the rigid visco-plastic model can accurately describe the semi-solid 60Si2Mn rolling process. The great deformation can achieve completely in view of low flow stress of semi-solid slurry.     

Evolution of microstructures in Al-Mn-Mg alloys during homogenization

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挤压温度对高纯铜组织演变规律的影响

为了研究挤压温度对高纯铜微观组织和变形行为的影响规律,通过反向挤压方式对高纯铜进行不同挤压温度下的挤压实验并观察了其显微组织.结果表明,随着挤压温度的升高,高纯铜的晶粒尺寸增大.当挤压温度为650 ℃时,挤压棒材的平均晶粒尺寸为36 μm;当挤压温度升至800 ℃时,挤压棒材的平均晶粒尺寸为51 μm.随着变形量的增加,当挤压温度为650~700 ℃时,压余变形区的平均晶粒尺寸趋向于由60 μm变为45 μm;当挤压温度为750~800 ℃时,平均晶粒尺寸则趋向于由90 μm变为75 μm.800 ℃挤压变形后晶粒内部出现大量以Σ 3特殊晶界为孪晶界的<111>60°退火孪晶.     

巨磁热效应合金Gd5Ge2(Si2-xMx)的结构和显微组织

通过用热稳定元素Mn和A l代替Gd5S i2Ge2合金中的(S i Ge)后对合金的晶体结构、显微组织和磁性能的影响研究表明,少量的掺杂量不会改变Gd5S i2Ge2的单斜型晶体结构,但它的晶格常数增大,体积膨胀,居里温度提高,然而掺杂样品的磁热效应降低.样品的显微组织随着热稳定元素Mn和A l掺杂量的增加,晶粒在长大,同时第二相析出量也在增加.     

Cu含量对汽车车身板用Al-1.0Mg-1.0Si-0.6Mn合金显微组织的影响

采用金相、SEM/EDS、XRD等研究了Cu含量对汽车车身用Al-1.0Mg-1.0Si-0.6Mn（in wt.%）铝合金结晶相及合金板材晶粒的影响规律.结果表明：Al-1.0Mg-1.0Si-（0.1~0.7）Cu-0.6Mn合金中主要存在部分可溶的浅灰色不规则条块状Al8（FeMn）2Si和黑色条块状或骨骼状结晶相Mg2Si,及完全可溶的球状或椭球状主要含Al1.9CuMg4.1Si3.3多相共晶产物;随着Cu含量增加,铸态合金中主要含Al1.9CuMg4.1Si3.3的共晶产物数量逐渐增多,而Mg2Si和Al8（FeMn）2Si结晶相变化不明显;同时,固溶后合金板材的再结晶晶粒变得越来越细,尽管Cu含量对合金冷轧板的晶粒尺寸影响不明显.     

热变形行为对20钢奥氏体晶粒形貌的影响

20#钢作为冷镦钢线,若出现混晶时,严重影响产品的质量.采用热模拟压缩变形试验的方法,研究了变形温度和变形量对低碳钢奥氏体晶粒形貌的影响.结果表明,变形量对奥氏体晶粒形貌有显著的影响,而变形温度的影响较小;在950℃变形量为30%～50%时混晶现象最严重.为工业生产提供了技术原型.     

Microstructural morphology of the semi-solid high carbon steel T12 before and after rheo-rolling

The semi-solid high carbon steel T12 was rolled in a closed box groove under a certain condition by the rheo-rolling equipment, and the microstructural morphology of the semi-solid T12 before and after deformation was investigated by optical microscope to analyze and summarize the microstructure evolution law of T12 deformed in semi-solid state. The experiment results show that the grain shape before deformation of the semi-solid T12 steel displays globule or ellipse by the electromagnetic stirring,the distribution of solid and liquid phases is homogeneous. But the microstructure of semi-solid product after rheo-rolling exhibits macrosegregation that the distribution of liquid and solid phases changes, the liquid phases divorce from the solid phases. In the transverse section, most of the solid phases get together in the center of the specimen, the liquid phases flow to the surface or the edge of the specimen, and the grains occur plastic deformation while reduction increased. In longitudinal section, the middle microstructure of the specimen is more homogeneous than that at the head or tail, the head microstructure is similar to the tail and the size of the grains is not homogeneous.     

Microscopic characterization of semi-solid aluminium alloys

The microstructural evolution and element distribution of the Al-4Cu-Mg alloy during semi-solid compression were investigated,and the precipitate behavior and dislocation morphology were discussed.The experimental results show that the microstructure,the number of CuAl2(θ phase) precipitates,and the dislocation density of the Al-4Cu-Mg alloy depend apparently on the process parameters.More segregation of Cu at the grain boundary happens with an increase of deformation temperature and a decrease of strain ra...     

Effect of austenitizing temperature on microstructure in 16Mn steel treated by cerium

The change of inclusions and microstructure of 16Mn steel treated by Ce were observed,and the effect of austenitizing temperature on the microstructure was also examined.The results show that the inclusions are transformed from Si-Mn-Al composite oxide and MnS into AlCeO3,Ce2O2S,and MnS composite inclusions after being treated by Ce.Plenty of intragranular ferrites are formed in 16Mn steel conraining ～0.017wt％ Ce.A large amount of intragranular acicular ferrites are formed after being austenitized for 20 min at 1473 K.The prior austenite grain size fit for the formation of intragranular acicular ferrites is about 120 μm.     

变形温度对细晶高强IF钢应力-应变曲线及显微组织的影响

以细晶高强IF钢为研究对象,在东北大学轧制技术及连轧自动化国家重点实验室MMS-300热力模拟实验机上,测定了在变形速率为10s^-1,真应变为0．5,变形温度分别为750、800、850、900、950、1000℃时的应力应变曲线。通过实验发现,钢的应力应变曲线为动．态回复型,不随温度而变化;流变应力随着变形温度的增加而下降;通过显微组织观察发现,随变形温度的降低,晶粒变细。     

温度、应变率和晶粒对Mn18Cr18N钢高温塑性的影响

通过拉伸热模拟试验研究了温度、应变率和晶粒尺寸对Mn18Cr18N高氮奥氏体不锈钢高温塑性的影响。结果表明：在800℃~1 200℃温度范围内,Mn18Cr18N高氮奥氏体不锈钢的塑性随温度升高而升高,1 200℃时达到最好,然后开始下降;应变率通过再结晶的作用而影响塑性;当温度低于1100℃时,细晶粒尺寸材料的塑性优于粗晶粒尺寸,而温度高于1 100℃时中等晶粒尺寸材料塑性最好。     

Performance of Semi-solid Slurry Produced by Twin-screw Stirring Mixer and Rheo-diecasting Process of AZ91D Alloy

The microstructure of semi-solid slurry of AZ91D alloy, which was produced by twin-screw stirring mixer under the different parameters, was investigated. Rheoforming by cold chamber die casting process was performed thereafter. The results indicate that with decreasing of the barrel temperature of the mixer and the pouring temperature of molten Mg alloy, the solid fraction of semi-solid slurry increases and the size of non-den-dritic grains becomes smaller. While the shear rate increases, the solid fraction of semi-solid slurry decreases. The tensile strength and elongation of metal rheoformed by die casting are higher by about 37% and 44% respectively than those produced by conventional liquid die casting.     

Grain boundary characteristics and tensile properties of Ti14 alloy after semi-solid deformation

The microsuucture and room-temperature tensile properties of Til4,a new α+Ti2Cu alloy,were investigated after conventional forging at 950℃ and semi-solid forging at 1000 and 1050℃,respectively.Results show that coarse grains and grain boundaries are obtained in the semi-solid alloys.The coarse grain boundaries are attributed to Ti2Cu phase precipitations occurred on the grain boundaries during the solidification.It is found that more Ti2Cu phase precipitates on the grain boundaries at a higher semi-solid forging temperature,which forms precipitated zones and coarsens the grain boundaries.Tensile tests exhibit high strength and low ductility for the semi-solid forged alloys,especially after forging at 1000℃.Fracture analysis reveals the evidence of ductile failure mechanisms for the conventional forged alloy and cleavage fiacture mechanisms for the alloy after semi-solid forging at 1050℃.     

Isothermal grain growth of reactive spray formed 7075 alloys in semi-solid state

The grain growth behavior in reactive spray formed 7075 2.91vol%TiC AI alloy was studied and compared with that of spray formed 7075 AI alloy at semi-solid state. The effects of in-situ TiC particles on the microstructure of spray formed 7075 AI alloy were also investigated. The specimens were heat-treated isothermally at various temperatures between the solidus and liquidus of 7075 A1 alloy for times in the range of 10-60 rain, then quenched in water. The microstructure of reheated specimens was characterized using scanning electron microscopy and optical microscopy. The grain size was measured using a mean linear intercept method. Results show that the in-situ TiC particles can effectively retard grain growth and refine the grain at a limited size. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates that the in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solid state.     

轧制对真空压铸AM50薄板组织与性能的影响

为研究真空压铸态AM50镁合金薄板在不同轧制变形量下组织和力学性能的变化,利用小型轧机对该合金进行多道次轧制,并进行了微观组织观察和室温拉伸性能测试.结果表明：该镁合金在常温下可进行多道次的轧制,但每道次之间要进行310℃×10min的退火处理,总变形量可达到45%;随总变形量的增加,轧制流线逐渐形成,晶粒变形成长条状,平均尺寸逐渐变小;变形量为40%时,沿轧制方向晶粒大约为2~4μm,轧制延展方向晶粒大约为5~10μm;随变形量的增大,材料的强度和塑性均在增加,而在总变形量达到40%时,材料的强度和塑性达到极值,屈服强度为282MPa,抗拉强度为329MPa,伸长率为8.8%.     

Property and microstructure analysis of ZK60 alloy superplastic sheet

It was investigated that the superplastic mechanical properties of fine-grained ZK60 magnesium alloy sheets at the temperature range of 200-420 ℃ and strain rate range of 5.56 × 10-4 -5.56 ×10-2 s-1 by tensile tests.And the microstructure evolution during the superplastic deformation of ZK60 magnesium alloy was examined by metallurgical microscope and transmission electronic microscope (TEM).The results showed that fine-grained ZK60 magnesium alloy starts to exhibit superplasticity from 250 ℃ and the maximum elongation is about 1106% at 400 ℃ and 5.56 × 10-4 s-1.The strain rate sensitivity is significantly enhanced with the increase of temperature and with the decrease of strain rate.The predominate superplastic mechanism of ZK60 magnesium alloy is grain boundary slide (GBS) at the temperature range of 300-400 ℃.The grains of ZK60 alloy remain equaxial after superplastic deformation,and dynamic continuous recrystallization (DCRX) is an important softening mechanism and grain stability mechanism during the superplastic deformation of the alloy.The curved grain boundaries and crumpled bands at grain boundaries after deformation prove GBS generates during superplastic deformation of ZK60 magnesium alloy.     

塑性变形及晶粒度对装饰铜合金腐蚀性能的影响

着重研究了ＮＺＳ系列装饰铜合金在不同塑性变形下的腐蚀性能。同时对晶粒度、退火温度对腐蚀性能的影响做了一定的探讨。实验结果表明：机械变形对ＮＺＳ系列装饰铜合金的腐蚀性能影响很大，腐蚀速率随变形量的增加而明显增加，增加晶粒度使铜合金的腐蚀性明显下降。     

Microstructure Evolution of Semi-solid Processed Hyper-eutectic Al-30%Si Alloy

Semi-solidmetalformingtechnologyhasachievedgreatprogressinthepasttenyearsbecauseitoffersmanypotentialadvamagessuchasformingnet-shapeparts,decreaseofmicrosegregation,reductionofporosity[1--3].Thistechnologyhasbeenappliedinproductionofsomehypo-eutectic...     

微合金非调质40Mn2V钢管的变形抗力研究

采用Gleeble-1500热模拟实验机对微合金非调质40Mn2V钢管的变形抗力进行了研究。结果表明,变形温度越高,变形速率越低,钢管变形抗力越小。变形抗力对数值lnσ随着温度升高和变形速率对数值ln ε的增大,分别呈线性减小和线性增大,且变形抗力与变形程度呈非线性关系。采用Matlab软件拟合出了微合金非调质40Mn2V钢管的变形抗力公式,其拟合度R为0．9663。     

60Si2Mn弹簧钢碳化物快速球化工艺研究

从离异共析转变的原理出发,开发60Si2Mn弹簧钢的快速球化退火工艺.讨论加热温度对残留碳化物粒子数量和分布的影响规律以及残留碳化物粒子对碳化物快速球化的作用,研究冷却速度对相变模式的影响.结果表明快速球化退火中,加热温度过高,碳化物完全溶解,没有残留的碳化物作为后续形核核心,加热温度过低,片层状碳化物溶解、断裂不完全...