Optimization of thermomechanical processes in Cu-Cr-Zr lead frame alloy using neural networks and genetic algorithms

1 Introduction Copper alloys are the most popular lead frame alloys and are used in plastic packag-ing application due to high thermal and electrical conductivity as well as high strength[1-3]. The thermomechanical treatment technology is one of the most used methods to attain high mechcanical and electrical properties of the copper alloys[4-6]. The thermomechanical processes have been mainly studied empirically with the trial-and-error method so far. There are few reports in the literature de…     

Texture of deformed Cu-Cr-Zr alloys

The influences of plastic deformation, aging treatment, and alloying elements on the texture of Cu-Cr-Zr alloys were explored. The texture component and intensity of Cu-Cr-Zr alloys under various working conditions after aging treatment were characterized using the orientation distributing function (ODF). The influence of Zr content on the texture of Cu-Cr-Zr alloys was also analyzed. The reduction pass and deformation level were primary factors influencing the texture. Rolling texture appeared in a rolled plate and the fibrous textures of {111} and {001} were detected after 80% deformation. Fibrous texture with a main constituent of {111} improved the tensile strength of the alloy wire. The texture contents of {110}<331> and {110}<112> were predominated, whereas, those of {113}<332> and {112}<111> were in the minority in the Cu-Cr-Zr alloy with a higher Zr content (>0.5wt%). However, in the samples with a lower Zr content (<0.1wt%), the texture contents of {113}<332>, {112}<111>, and {111}<110> were in the majority.     

Al-Pb偏晶合金凝固过程中贫Pb层的形成机理

对Al-Pb偏晶合金开展了快速定向凝固实验,试样组织观察表明,在试样表面形成了一贫Pb层;建立了偏晶合金定向凝固过程中液-液相变的理论模型,模型中考虑了液滴的形核、扩散长大、液滴的空间迁移以及熔体的对流运动的影响。根据实际凝固条件进行了相关模拟计算,结果表明在凝固界面前沿存在一过冷区,在过冷度的峰值点附近弥散相液滴形核;贫Pb层的形成是形成相与坩埚的润湿性、液滴的径向迁移和熔体的对流运动共同作用的结果.     

Effects of aging parameters on hardness and electrical conductivity of Cu-Cr-Sn-Zn alloy by artificial neural network

In order to predict and control the properties of Cu-Cr-Sn-Zn alloy, a model of aging processes via an artificial neural network (ANN) method to map the non-linear relationship between parameters of aging process and the hardness and electrical conductivity properties of the Cu-Cr-Sn-Zn alloy was set up. The results show that the ANN model is a very useful and accurate tool for the property analysis and prediction of aging Cu-Cr-Sn-Zn alloy. Aged at 470–510 °C for 4-1 h, the optimal combinations of hardness 110–117 (HV) and electrical conductivity 40.6–37.7 S/m are available respectively.     

Mg含量对Al-Cu-Mg合金定向凝固组织的影响

建立模拟多元合金树枝晶生长的三维元胞自动机模型,耦合合金热力学和生长动力学计算,模拟预测Al-Cu-Mg合金定向凝固组织形成过程,考察Mg含量对定向凝固一次枝晶间距的影响。结果表明,在相同凝固条件下,定向凝固一次枝晶间距随着Mg含量的增加而增大,定向凝固二次枝晶间距随着Mg含量的增加而减小。     

快速凝固Mg-6wt．％Zn合金的制备及微观组织研究

采用雾化-双辊急冷法成功制备了快速凝固Mg-6Zn合金薄片,并利用扫描电子显微镜、X射线衍射仪、差示扫描分析和透射电子显微镜对该合金的微观组织和物相种类进行了分析。结果表明,快速凝固Mg-6Zn合金具有细小的等轴晶组织,其相组成为α-Mg和Mg51Zn20,以及少量的MgZn2和Mg2Zn3;与铸态合金相比,合金的微观组织显著细化,同时合金中存在一定数量的位错。     

Directional solidification and physical properties measurements of the zinc-aluminum eutectic alloy

Zn-5wt％ Al eutectic alloy was directionally solidified with different growth rates (5.32-250.0 tm/s) at a constant temperature gradient of 8.50 K/mm using a Bridgman-type growth apparatus.The values of eutectic spacing were measured from transverse sections of the samples.The dependences of the eutectic spacing and undercooling on growth rate are determined as λ=9.21 V-0.53 and △T=0.0245 V0.53,respectively.The results obtained in this work were compared with the Jackson-Hunt eutectic theory and the similar experimental results in the literature.Microhardness of directionally solidified samples was also measured by using a microhardness test device.The dependency of the microhardness on growth rate is found as Hv=115.64V0.13.Afterwards,the electrical resistivity (r) of the casting alloy changes from 40× 10-9 to 108× 10-9 Ω·m with the temperature rising in the range of 300-630 K.The enthalpy of fusion (△H) and specific heat (Cp) for the Zn-Al eutectic alloy are calculated to be 113.37 J/g and 0.309 J/(g.K),respectively by means of differential scanning calorimetry (DSC) from heating trace during the transformation from liquid to solid.     

海上风电机组用N38SH永磁体在盐雾中的性能

针对风电机组在生命周期内始终受到盐雾、湿热环境影响的问题,研究了发电机中永磁体在海洋盐雾环境下的性能变化.通过盐雾腐蚀试验,模拟发电机用N38SH永磁体的服役环境,研究其在盐雾腐蚀条件下磁性能的变化,为海上风电机组永磁体的保护提供理论依据.试验结果表明,无论有无镀层保护,盐雾腐蚀将极大程度影响永磁体的磁性能,特别是在剩余磁感应强度和矫顽力等性能指标下降较多时,需要专门的保护措施.     

Transient spinodal decomposition during annealing of rapidly solidified Al-10Sr alloy

Rapidly solidified Al-10Sr alloy ribbons were prepared using a single roller melt spinning technique. The annealing process of the rapidly solidified Al-10Sr alloy has been carried out using differential scanning calorimetry (DSC). The microstructure of as-annealed Al-10Sr alloy has been characterized by transmission electron microscopy (TEM). The equilibrium AUSr phase is dominant in the as-annealed alloy. Besides the Al4Sr phase, an AlSr phase is also found in the alloy isothermally annealed at 873 K for 90 min. Furthermore, a modulated nanostructure was observed in the alloy isothermally annealed at 873 K for 90 min. With further prolonged annealing time, however, the AlSr phase disappears in the as-annealed alloy. The dependence of particle size and growth rate on annealing time as well as the modulated structure shows that the occurrence of the AlSr phase may be due to the spinodal decomposition.     

Rapid directional solidification in Sn-Cu lead-free solder

1. Introduction In recent years, increasing environmental and health concerns over the toxicity of lead combined with the strict legislation to ban the use of lead-based solders have provided an inevitable driving force for the de- velopment of lead-free …     

Effects of rapid solidification process and 0.1%Pr/Nd addition on characteristics of Sn-9Zn solder alloy and interfacial properties of Cu/solder/Cu joints

Rapidly solidified Sn-9Zn-0.1Pr(/Nd) alloy foils were prepared by melt-spinning method. Through comparison, the effects of rapid solidification process and 0.1%Pr/Nd(mass fraction) addition on the microstructure, thermodynamic characteristic of Sn-9Zn solder alloy were analyzed. The tensile-shear tests were used to evaluate the mechanical properties of solder/Cu joints. The results show that the rapid solidification process can greatly refine the microstructure of Sn-9Zn-0.1Pr(/Nd) alloys. After rapid solidification, the effects of Pr/Nd addition on microstructure are depressed. The pasty range of the rapidly solidified Sn-Zn-RE solders is also reduced significantly. The mechanical properties of solder/Cu joints are obviously improved using the rapidly solidified Sn-9Zn-0.1Pr(/Nd) solder alloy, which results in the formation of uniform interface. The promotion effect of Nd addition in Sn-9Zn alloy on the interfacial reaction of solder/Cu joint is more remarkable than that of Pr.     

Prediction of the solidification structure of casting and heterogeneous nucleation

The frequency of heterogeneous nucleation during the solidification of Al-Si binary alloy was estimated by comparing experimentally obtained macrostructures of castings with numerically simulated ones. A molten alloy was unidirectionally solidified from a water-cooled copper chill in an adiabatic mold. The location of columnar to equiaxed transition (CET) in the solidified alloy ingot was measured. A numerical simulation for grain structure formation based on the Monte Carlo method was carried out, and the frequency of heterogeneous nucleation in the alloy was evaluated by producing similar structure with the experimental one. The frequency of heterogeneous nucleation was expressed as a probabilistic function with an exponential form of undercooling that determines the probability of nucleation event in the simulation. The value of the exponent is regarded as the nucleation parameter. The nucleation parameter of Al-Si binary alloy varied with initial Si content.     

基于表观黏度模型的AZ31流变铸轧数值模拟

以AZ31半固态合金为研究对象,应用流体模拟软件Fluent对其铸轧过程进行研究。通过使用简单等温稳态黏度模型、Carreau黏度模型、简单连续冷却黏度模型、黏度不变模型,得到了相应的铸轧温度分布、流场分布以及黏度分布,并进行了比较和分析。结果表明：在特定工况下,为保证出口处的合金刚好凝固而不会造成铸轧不成形或铸轧中断的最佳浇铸温度为880 K,此时Carreau黏度模型最适合AZ31半固态合金的铸轧过程。     

复合工艺制备的半固态A356铝合金初生相形貌分形特征研究

利用复合工艺制备了A356铝合金半固态浆料,研究了半固态A356铝合金初生相形貌的分形特征．应用编制的计算程序计算了半固态A356铝合金初生相形貌的分形维数．结果表明,复合工艺制备的半固态A356铝合金初生相的形貌可以用分形维数来表征,不同工艺参数下所获得的半固态初生相形貌具有不同的分形维数．铸锭中不同部位半固态初生相的形貌具有不同的分形维数,反映了同一铸锭不同部位的凝固条件对半固态初生相形貌的影响．凝固组织中的每个半固态初生相的分形形貌均为系统耗散性的几何表现．     

快速凝固Ni50Al50合金加氢催化剂的研究

以旋铸法制备快速凝固Ｎｉ５０Ａｌ５０合金条带,经球磨、活化处理后制成了骨架镍催化剂．利用金相检验,ＸＲＤ,ＢＥＴ等技术对催化剂的整体结构和表面状态进行分析,发现快凝催化剂与常规催化剂相比,具有较小的比表面积,相似的晶粒度和略大的点阵参数．对比研究了常规骨架镍催化剂和快凝骨架镍催化剂的油脂加氢性能,结果表明,在相同的化学反应条件下,快凝骨架镍的油脂加氢活性比常规催化剂的高出约０．５倍．     

元胞自动机法模拟Al-4．5mass％Cu枝晶生长

通过引入溶质再分配、溶质扩散、界面能各向异性和界面曲率,构建了描述合金凝固微观组织形态演变的2D元胞自动机模型。并用该模型研究了Al-4.5mass%Cu合金凝固过程中树枝晶长大过程。结果表明:该模型较好地描述了枝晶生长、晶间和枝晶偏析。凝固过程中的溶质再分配直接影响着树枝晶的生长形貌和微观偏析形成。成份过冷是液/固界面失稳的主要原因,激发二次晶或三次晶产生。二次晶生长是相互竞争的过程,在成分过冷和曲率过冷作用下,二次晶根部溶质富集程度大,出现明显的"颈缩"。在枝晶生长过程中,枝晶间会形成小范围、高溶质浓度的孤立液体区域,形成晶间偏析或点偏析,树枝晶形貌对晶间偏析程度影响较大。在各枝晶臂上,先凝固部分溶质浓度较后凝固部分溶质浓度低,并且中心溶质浓度较边缘处溶质浓度低,形成枝晶偏析,枝晶偏析在枝晶的亚稳态生长阶段更显著。     

New method for the preparation of semi-solid AISi7Mg alloy slurry

The effects of pouring temperature and short electromagnetic stirring with low strength on the microstructures of AlSi7Mg alloy were investigated.The results show that if liquid AlSi7Mg alloy is poured at 630 or 650 ℃,many primary α-Al grains in the solidified melt are rosette-like,and only a small number of them are spherical.However,if liquid AlSi7Mg alloy is poured at a lower superheat and meanwhile is stirred by an electromagnetic field at a low power for a short time,then most primary α-Al grains in the solidified melt become spherical,and only a few are rosette-like.The theoretical analysis indicates that the strengthened melt flow motion induced by the short electromagnetic stirring makes the temperature field more homogeneous in the melt,which is poured at a lower superheat,and makes the primary α-Al grains deposit in a larger region at the same time,so this new solidification kinetic condition leads to the microstructure of spherical primary α-Al grains.The experiments also demonstrate that pouring at an appropriate superheat and stirring by an electromagnetic field at a low power for a short time is a good new method for preparing the semi-solid slurry or billet of AlSi7Mg alloy.     

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)     

Al2O3/ZL101-La合金复合材料凝固组织与溶质偏析的研究

利用挤压铸造法制备了Al2O3/ZL101-La复合材料,研究了稀土La对复合材料凝固组织以及基体合金凝固时溶质偏析的影响.结果表明,稀土La可细化基体合金的凝固组织,并且富集在界面附近,有利于改善铝合金液对氧化铝短纤维的润湿性,但是未发现任何富稀土相在界面上形成.稀土La对基体合金中的镁的偏聚没有很明显的影响,镁和稀土La均在界面处富集,且它们的分布位置大致近似.     

Structural Characteristics and Properties of Precious Metal Powders and Copper Powder Prepared by High-speed Centrifugal Atomization Technique

The rapidly solidifiedtechnique brings a series of new metastable metals and alloys,such as amorphous met-als,quasicrystals,microcrystalline and nanocrystals.The major advantages of the technique lie in the fact that itcani mprove the solubility of alloys…