EET research on the Al-22%Si alloy under the action of electric pulses

Based on the empirical electron theory of solids and molecules (EET), the phase valence electron structure parameters of Al-22%Si alloy are calculated, and the sensitivity of the bond network of Al-Si alloy melt to temperature (energy) and the effect of the sensitivity on the morphology are studied. The results show that the Si-Si clusters with larger n _A in the slightly superheated Al-Si alloy melt supply the nucleation core to the primary silicon phase in the hypereutectic Al-22%Si alloy, and strongly generate the drag-like effect for the Al-Si clusters around them; that the variation of temperature significantly affects the stability of bonds of the core so that the solidified structure is changed; that the electric pulse applied to the alloy melt can irrecoverably alter the stability of Si-Si clusters, then the modification of the solidified structure morphology of alloys is generated; that the higher the energy of the electric pulse, the less stable the Si-Si clusters, and the more significant the electric pulse modification. Supported by the National Natural Science Foundation of China (Grant No. 50674054), and the College Key Laboratory Open Fund of Liaoning Province(Grant No. 200516203)     

铝硅合金潜热变化规律的DSC分析

通过真空电弧炉制备不同Si质量分数的铝硅合金,利用差示扫描量热分析仪测量合金的潜热,分析了Al-Si合金的成分与潜热之间的相互关系。结果表明,Al-Si合金初生相和共晶相的潜热需要进行单独求解,在Si的质量分数为4.16％～21.4％范围内,Al-Si合金潜热随Si的质量分数增加呈线性增加,亚共晶潜热、过共晶潜热具有不同的线性关系,分别为:L_hypo=353.4+12X(亚共晶)和L_hyper=409.6+7.54X (过共晶),其中X为Si的质量分数;过共晶Al-Si合金中初生Si相的潜热与纯Si的潜热相差较大是由Al-Si熔体中与纯Si熔体中Si的形态差异引起的。     

The Structural Evolutions of ZL109 Alloy and 7050 Alloy in the Semisolid Squeeze Casting Process

The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The thin and symmetrical structure was obtained by using low super heat casting process. The eutectic that lied in the raw billet of ZL109 alloy remelted and produced liquid phase in the process of remelting, but to the 7050 alloy, the eutectic of intergranular and the pointedness of grains was reme...     

Effect of P/M value on the preforms and microstructures of spray formed 70Si30Al alloy

A novel 70Si30Al alloy was prepared by the spray forming process for electronic packaging materials. The effect of the ratio of atomization pressure to metal melt mass flux rate （P/M） on the preforms and microstructures of the spray-deposited 70Si30Al alloy was studied. The results indicate that the PIM value has a considerable influence on the formation of the preforms and the optimal value is in the range of 0.209-0.231 MPa/（kg.min^-1）. The microstructure of the spray formed 70Si30AI alloy is fine and homogenous. The primary silicon phases distributing in the aluminum matrix evenly are fine and irregular. The aluminum matrix is divided into two groups： supersaturated α-Al phase or α-Al phase and Al-Si pseudoeutectic phase or Al-Si eutectic phase.     

Origin of the pre-peak in the structure factor of liquid Fe-4.30C-0.21Ce alloy

The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260 nm at the temperature range of 1200-1400℃, which increases to 0.269-0.271 nm with the addition of 0.21% (mass fraction) Ce in the Fe-C alloy at the same temperature range. There is a pre-peak at Q = 15.5 nm-1 on the original intensity curve and structure factor S(Q) of the liquid Fe-4.30C-0.21Ce alloy, which was caused by the Ce atoms in the C-Ce clusters. Combined with the shared face, the tetragonal structure can meet the requirement for the distance of Ce-Ce atoms. It also shows that the cluster size in the liquid Fe-4.30C-0.21Ce alloy increases with the decreasing temperature.     

The structural evolutions of ZL109 alloy and 7050 alloy in the semisolid squeeze casting process

The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The thin and symmetrical structure was obtained by using low super heat casting process. The eutectic that lied in the raw billet of ZL109 alloy remelted and produced liquid phase in the process of remelting, but to the 7050 alloy, the eutectic of intergranular and the pointedness of grains was remelted to make the grains more uniform and smooth. In the process of semisolid forming, the primary α and the eutectic inside the ZL109 alloy were separated partly and the grains in the 7050 alloy was conglutinated together. After heat treatment, the eutectic α grains of ZL109 traveled to primary α and shaped the white fishing net like organization; the eutectic Si grains assembled into the black massive particles. As to 7050, after heat treatment, α particles recrystallized and thin grains pattern was obtained.     

烧结与冷镦过程中铝硅共晶合金显微结构与密度的演变

采用烧结及后续的镦粗工艺制备了铝硅共晶合金块体材料,研究了烧结温度对烧结体显微结构、抗压强度及相对密度的影响。结果表明：烧结温度显著影响烧结体的显微结构和抗压强度,以临近铝硅共晶合金液相线的温度烧结时,发生了局部熔化,产生的熔融液体破坏了颗粒表面的氧化膜,颗粒之间相互黏结,形成了烧结骨架。以优化的555℃烧结,Si颗粒呈球状,抗压强度达到最佳,但相对密度未发生变化。在后续的冷镦过程中,烧结骨架及粉末颗粒均产生变形,孔隙减小,颗粒呈扁平状,相对密度达到了98%。     

ZL102合金热压缩变形力学性能和微观组织的研究

研究了不同压缩比对ZL102合金的显微组织及性能的影响．实验结果表明：ZL102在铸态结构组织下,其机械性能较差,但是在经过热压缩加工以后其抗拉强度有了不同程度的提高,并且和其变形量有着直接的关系,其中压缩比为85．81oA时抗拉强度增加幅度最大;ZL102经过热压缩以后,其塑性没有明显的改善;金相组织观察表明,随着变形量的增加,晶粒细化程度增大．     

液氮浸泡后在空气中暴露对ZL107力学性能的影响

将经过或未经过电解充氢的铝硅合金(ZL107)试样在液氮中浸泡后，再置于空气中一定时间，其抗拉强度有不同程度的改善．液氮保存及其后的暴露使ZL107中充入的氢外逸。而且在外逸的过程中试样的部分固溶氢也随之逸出，造成试样氢含量的下降。     

铸态硅酸铝短纤维／ZL109复合材料性能的实验研究

比较了铸态硅酸铝短纤维／ＺＬ１０９复合材料与ＺＬ１０９合金的机械性能,磨损性能及摩擦性能．结果表明,由于硅酸铝短纤维的加入,使抗拉强度提高４５％到１倍以上,抗压强度提高５０％到１倍以上,磨损性能提高,摩擦系数下降,且随着纤维含量的增加,复合材料的性能也随着提高．     

铝合金表面激光熔覆高硅涂层的组织与磨损性能

用7kW横流C02激光器在ZL101铝合金表面激光熔覆高硅涂层。探索不同激光功率熔覆对涂层质量的影响,分析涂层的微观组织,测试涂层的硬度和磨损性能。结果表明：在优化工艺参数下制备出的激光熔覆高硅涂层组织致密、无气孔和裂纹,激光熔覆层中存在大量初晶Si、α-Al树枝晶和共晶组织。涂层与基体结合区处呈现典型的外延生长特征,形成了良好的冶金结合。熔覆层的横截面硬度在HV150～320之间,是基体的2～3倍,并显著提高了基体的耐磨性能。     

Size distributions and magic number characteristics of cluster configurations formed during solidification processes of liquid metal Al

Recently, the studies on the stability and magic number characteristics of cluster con- figurations, especially of larger cluster configurations, have become a very active area in physics, chemistry and materials science[1―8]. However, at present, the experimental stud- ies are mainly carried out on fine powder obtained by means of physical or chemicalmethods (such as ionic spray, laser evaporation, air-actuated technology, gas discharging, and organic metal chemical reaction) [1-5], and the t…     

钎焊温度对SiC/YG8接头微观组织的影响

在保温时间为5min、钎焊温度为940~990℃条件下,采用CuMnNi钎料钎焊SiC陶瓷与YG8硬质合金.利用金相显微镜、扫描电镜和能谱仪对接头的微观组织进行分析,研究钎焊温度对接头微观组织的影响.结果表明:在靠近SiC一侧生成一层带状反应层,主要由Cu基固溶体、硅化物、碳和碳化物组成;焊缝主要由基底Cu基固溶体以及Mn、Si、Co、Cu、Ni元素形成的化合物组成.随着钎焊温度的增加,焊缝的宽度减少,焊缝中心的Cu基固溶体基底减少,而化合物相增多.     

用切割投影法探讨Cd—Yb二十面体准晶原子模型

在假定原子面为球形的情况下，采用切割投影矩阵得出准晶Cd—Yb三维空间的原子团簇，并与其近似相进行对比。结果表明，除了第一层（无序）外，其余三层原子团簇均相吻合。     

Al-Si合金回转件车削表面雪花斑形成机理

Al-Si合金回转件车削加工时,工件表面会产生明暗相间的雪花斑,影响工件使用性能.为了找到雪花斑产生的机理,针对ZL101铸件加工表面进行了粗糙度测量,并对工件有雪花斑和无雪花斑位置进行了力学性能测试和微观组织观察.结果表明:车削工件表面有雪花斑位置的粗糙度显著大于无雪花斑位置的粗糙度;该位置取样样品的强度小于无雪花斑位置取样样品的强度.微观组织观察表明,有雪花斑位置样品的α-Al相晶粒尺寸和枝晶间距显著大于无雪花斑的,且该位置共晶组织中的硅相颗粒尺寸及共晶组织所占比例均大于无雪花斑的.组织粗大和共晶组织的增加促使Al-Si合金切削加工过程中切削表面雪花斑的形成.     

铝硅合金热稳定性能的试验研究

利用自制热循环装置对储能铝硅合金进行热循环试验,研究了Si的质量分数12.07%的ZL102合金在不同热循环次数下的热稳定性能的变化,并对其结果进行了分析总结。试验结果表明:经过长达1 600次熔化-凝固循环后,铝硅合金的熔化起始温度随热循环次数的增加而略有上升,相变起始温度从579℃升高到584℃,熔化潜热略有下降,潜热值从537J/g下降到500.6J/g,铝硅合金在长期的热循环过程中有着优良和稳定的储热性能,可应用于高温太阳能热发电蓄热系统中。     

CuZn合金贝氏体预相变内耗

用低频倒扭摆内耗法研究了ＣｕＺｎ合金中贝氏体预相变。发现在贝氏体孕期内发生了溶质原子偏聚并形成溶质的贫化区与富化区，在内耗谱上出现偏聚过程内耗峰和弛豫内耗峰，用相关态理论解释弛豫内耗峰的形成机理。     

氧化SiCp增强ZL101铝基复合材料的显微结构

利用光学和电子显微镜研究了液态金属搅拌法处理后金属型铸造和连续铸造ＳｉＣｐ／ＺＬ１０１ 铝基复合材料的显微组织与界面结构特征．结果表明,ＳｉＣｐ 高温氧化后表面生成的ＳｉＯ２ 晶体在复合材料复合与铸造期间与铝合金熔液中的Ｍｇ 、Ａｌ 元素发生界面反应,生成ＭｇＡｌ２ Ｏ４ 和Ｓｉ,促使ＳｉＣｐ 与铝合金润湿,并提高ＳｉＣｐ 的分散性．与普通金属型铸造相比,连续铸造ＳｉＣｐ／ＺＬ１０１ 复合材料的晶粒细小,ＳｉＣｐ 分布十分均匀,ＳｉＣｐ／Ａｌ 界面反应层较薄．     

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.     

Liquid structure of pure iron by X-ray diffraction

The liquid structure of pure iron at 1540, 1560 and 1580℃ was studied by X-ray diffraction. The results show that near the melting point there is a medium-range order structure that fades away with the increasing temperature. The average nearest distance of atoms is almost independent of the melts temperature, but the average coordination number, the atom cluster size and the atom number in an atom cluster all decrease with the increasing temperature of the melt. Near the melting point there are a lot of atom clusters in the pure iron melt. The atom cluster of pure iron has the body-centered cubic lattices, which are kept from the solid state. And the body-centered cubic lattices connect into network by occupying a same edge. The atoms in the surrounding of the atom clusters are arranged disorderly.