半固态AlSi7Mg合金在封闭竖直圆柱空间中触变变形和流动的研究

兰固态合金挤压工艺的关键是控制半固态合金坯料的流动和变形。在实际工程应用中,半固态合金坯料的挤压铸造成形主要是通过在二维和三维约束空间中的变形和流动而实现的。本文论述了半固态ＡｌＳｉ７Ｍｇ合金坯料在三维封闭圆柱空间中触变变形和流动的规律。     

半固态AlSi7Mg合金触变成形实验装置的研究

设计并制造了一套半固态铝合金触变成形的实验装置,给出了触变成形实验的工艺参数,对实验结果与模拟仿真计算进行了对比,其二者的拟合度很好。     

半固态ZL101合金触变成形的本构关系

对半固态ZL101合金坯料进行等温压缩实验,研究变形温度、应变速率对半固态ZL101合金流动应力的影响。结果表明,半固态ZL101合金的流动应力随着变形温度的升高而降低,随着应变速率的增大而增大。DOE实验表明,应变速率对材料的流动应力影响较大。采用遗传算法对半固态等温压缩实验数据进行拟合,得到ZL101合金的本构关系,并将其导入到有限元程序中进行计算,模拟结果与实验结果基本吻合。     

温度和应变速率半固态Alsi7Mg合金变形性的影响

采用G1eeble-1500热模拟试验机研究了温度和应变速率对半固态AISi7Mg合金变形性的影响。从中得知，半固态合金的压缩流动应力不仅是变形温度的函数，而且是应变速率的函数，变形温度和应变速率决定了半固态压缩变形的特征。     

TiC—Ni金属陶瓷触变成形的力学模型研究

为研究TiC-Ni金属陶瓷的高温变形规律,利用Gleeble-2000热模拟实验机研究了TiC-Ni金属陶瓷的触变力学行为.通过回归分析建立了TiC-Ni、在950、1000和1050℃时的粘塑性本构关系模型,并对回归方程进行了数理统计检验,检验指标在95%置信区间内可以被接受.     

温度和应变速率对半固态AlSi7Mg合金变形性的影响

采用Gleeble-1500热模拟试验机研究了温度和应变速率对半固态A1Si7Mg合金变形性的影响。从中得知,半固态合金的压缩流动应力不仅是变形温度的函数,而且是应变速率的函数,变形温度和应变速率决定了半固态压缩变形的特征。     

AlSi10Cu2Mg合金的半固态触变成形

结合汽车零件所用的材质 ,研究了AlSi10Cu2Mg合金的半固态坯料制备、部分重熔及空压机连杆的半固态触变挤压铸造成形 ,显示了该技术在铝合金汽车零件生产中的优越性     

AlSi10Cu2Mg合金的半固态触变成形

结合汽车零件所用的材质,研究了AlSi10Cu2Mg合金的半固态坯料制备、部分重熔及空压机连杆的半固态触变挤压铸造成形,显示了该技术在铝合金汽车零件生产中的优越性。     

新型倾斜板技术制备半固态AlSi6Mg2合金及触变成形

采用自制的波浪型倾斜板技术装置，对制备半固态AlSi6Mg2合金坯料及触变成形进行研究。结果表明，采用波浪型的倾斜板可制备组织性能优良的半固态合金坯料，坯料由细小的球形晶和少量玫瑰晶组成。在本试验条件下，制备AlSi6Mg2半固态坯料的浇注温度范围为660～680℃。在坯料二次加热温度为597℃，保温90min，模具预热温度为400℃，保温120min的试验条件下，可得到表面光洁、组织优良的成品制件。触变压铸时，液相流动成为主要的变形方式，制品上部由于液相偏聚，对应的硬度较低，下部由于固相的微塑性变形，对应的硬度较高。     

AlSi7Mg合金半固态成形件的热处理工艺

利用电阻炉加热，采用正交设计方法，优化了半固态A356铝合金触变成形件轴瓦盖的热处理工艺，并进行了硬度测试。结果表明：半固态成形后的轴瓦盖T6处理的最佳工艺制度为固溶温度535℃，固溶时间10h，时效温度165℃，时效时间5h。其硬度值(HV)为116．85MPa，此时析出相分布均匀，组织细小。     

半固态AlSi7Mg合金二次加热工艺与组织转变机制

采用电阻炉对用电磁搅拌方法制备的半固态ＡｌＳｉ７Ｍｇ合金二次加热,结合金相分析研究了半固态组织的转变机制。实验发现,共晶相中的Ｓｉ相通过向α相中扩散溶解,其形状从片层状断裂成点链状颗粒,并随着温度升高颗粒细化球化。片层越薄,这一过程发生的温度越低,速度越快。Ｓｉ溶解到一定程度后共晶部分熔化,初生α相形状、尺寸开始变化。树枝状α相和蔷薇花状α相球化,但前者变大,后者变小为原始尺寸的１／２－１／４。近     

AlSi7Mg合金半固态连铸坯料和组织形成研究

研究了电磁搅拌对半固态ＡｌＳｉ７Ｍｇ合金连铸坯料组织的影响,研究结果表明,电磁搅拌功率是重要的影响因素,搅拌功率越大,球状的初生α－Ａｌ端部形态越圆整,蔷薇状的初生α－Ａｌ越少,尺寸越小,宫铸坯表层的枝晶层越薄;连铸坯料中的出现大量球状初生α－Ａｌ是蔷薇状初生α－Ａｌ二次臂熔断的结果,连铸坯料中出现许多蔷薇状初生α－Ａｌ结果是其二次臂未充分熔断所致。     

AlSi7Mg合金坯料在固液两相区的初始结构对变形的影响

本文论述了Ａ１Ｓｉ７Ｍｇ合金在半固态下的初始结构对压缩变形行为的影响。结果表明：Ａ１Ｓｉ７Ｍｇ合鑫产的初妈显微结构的固想颗粒尺寸及分布、颗粒形貌、颗粒团聚化程度对兰固态合金坯料的表观粘度有重要的影响。具有初始细昌结构（蔷薇状结构）的合金应力水平较低,具有中等枝晶和粗枝晶结构的合金应力水平较高。非枝晶组织半固态合金变形时固相颗粒变形力的传递数学模型：σｓ＝α２λ１／λ２（Ｔ）ηｆε。     

半固态ZA12合金的瞬态流变性能

采用自行研制的高温同轴双筒流变仪对半固态ＺＡ１２合金的流变性能进行研究,结果表明。半固态合金的剪切应力与剪切时间的关系曲线的特征与固相分数和剪切速率有关,此外,在稳态条件和瞬态条件下,半固态合金浆液表现出不同的流体特征。     

THE APPARENT VISCOSITY OF SEMI-SOLID AZ91D ALLOY AT STEADY STATE

The rheological behavior of semi-solid AZ91D at steady state is studied using a Couette type viscometer in the present paper. The results show that the apparent viscosity of semi-solid AZ91D at the steady state increases with the solid fraction increasing, and goes up sharply when the solid fraction reaches a certain value, which is called critical fraction. In addition, the apparent viscosity of semi-solid AZ91D at the steady state takes on a distinct downtrend with the shearing rate increasing, which indicates a strong shear thinning property. In addition, the critical solid fraction becomes higher under larger shearing rate, owing to the more globular shape of the solid particles. Based on the present experiment results, an empirical equation is built as that, relating the steady state apparent viscosity of semi-solid AZ91D with the solid fraction fs andshearing rate (?) at the same time: ηapp=10.74exp(6.95fs)(?)-0.86.     

ARTIFICIAL NEURAL NETWORK MODEL OF CONSTTTUTIVE RELATIONSHIP FOR 2A70 ALUMINUM ALLOY

The hot deformation behavior of 2A70 aluminum alloy was investigated by means of isothermal compression tests performed on a Gleeble-1500 thermal simulator over a wide range of temperatures 360-480℃ with strain rates of 0.01-1s-1 and the largest deformation of 60%, and the true stress of the material was obtained under the above-mentioned conditions. The experimental results shows that 2A70 aluminum alloy is a kind of aluminum alloy with the property of dynamic recovery; its flow stress declines with the increase of temperature, while its flow stress increases with the increase of strain rates. On the basis of experiments, the constitutive relationship of the 2A70 aluminum alloy was constructed using a BP artificial neural network. Comparison of the predicted values with the experimental data shows that the relative error of the trained model is less than ±3% for the sampled data while it is less than ±6% for the non- sampled data. It is evident that the model constructed by BP ANN can accurately predict the flow stress of the 2A70 alloy.     

ARTIFICIAL NEURAL NETWORK MODEL OF CONSTITUTIVE RELATIONSHIP FOR 2A70 ALUMINUM ALLOY

1. Introduction Lately, with the rapid development of the computation technique, the finite element method is more and more applied to the numerical simulation of the metal forming process. The constitutive relation- ship, namely, the relationship between…     

以Zener—Hollomon参数表示的GH169合金的本构关系

根据ＧＨ１６９合金在Ｔｈｅｒｍｅｃｍａｃｓｔｏｒ—Ｚ型热加工模拟试验机上进行等温恒应变速率压缩试验数据提出一种以Ｚｅｎｅｒ—Ｈｏｌｌｏｍｏｎ参数（简称Ｚ—Ｈ参数）表示，从而可以直接研究该合金锻造热力参数的本构关系：其中Ｚ为Ｚ—Ｈ参数；Ｄ０、Ｄ１、Ｄ２、Ｄ３均为等效应变的函数。在绝大多数情况下，计算结果与实验数据的误差不超过７％。对ＧＨ１６９合金锻造过程用有限元法进行数值模拟时，采用本文提供的本构关系将使公式推导过程简化，计算时间大幅度减少。     

半固态AZ91D镁合金的压缩变形研究

利用Gleeble 1500热模拟机对半固态AZ91D镁合金的变形规律进行了研究．结果表明：当应变速率相同时,变形温度越高,半固态AZ91D镁合金试样的变形应力就越低;当应变速率和变形温度相同时,半固态球状晶试样的压缩变形应力明显低于枝晶试样的压缩变形应力;变形量对半固态压缩试样的应力一应变关系的影响很小．当应变速率为0．1,10s^-1和变形温度为48m-556℃时,球状晶和枝晶试样的稳定压缩应力分别为3—17．13MPa和6—31．6MPa．当变形温度为508℃和应变速率为0．01—20s^-1时,球状晶和枝晶试样的稳定压缩应力分别为4．78-9．09MPa和7．87-26．21MPa。     

STATISTICAL MODEL FOR FRACTURE TOUGHNESS OF A MODIFIED Al-7Si-0.45Mg CAST ALLOY

The statistical model for the fracture toughness of a modified Al-7Si-0.45Mg cast alloy hasbeen proposed on the basis of analysis of the correlation between the size distribution of cracknuclei and Si particles and of the micromechanism of fracture.The suitable criterion of frac-ture toughness according to the model has been given.The model has found a good explana-tion for the fracture feature,fracture toughness and microstructure,and agreed with the ex-periments very well.