影响钢凝固组织的因素及其改善措施

本文综合论述了钢的凝固组织，影响钢的凝固组织的因素以及几种主要改善钢的凝固组织的技术措施。     

太阳能电池多晶硅铸锭的凝固原理和方法浅谈

首先从定向凝固的原理讲起,其中涉及定向凝固的一些重要的工艺参数以及多晶硅铸锭的组织结构;其次,介绍了多晶硅铸锭的几种凝固方法,尤其着重讲了一下热交换法的应用;并在结尾提到了现在铸锭法中需要改进和解决的主要问题。     

锡铅合金的热型连铸

热型连铸Ｓｎ４０％Ｐｂ时，用连续测温方法测定铸型出口处不同温度下的型内温度分布。由此求得固＋液区的长度、位置和温度梯度等数据。发现随着铸型温度的提高，固＋液区变短并向型出口移动；温度低于２１６℃时，由于固＋液区长而形成热裂，高于此温度热裂消除并获得光洁表面；温度梯度大于０．３９℃／ｍｍ时实现等轴晶向柱状晶的转变。     

水泥固化体撞击影响研究

本文进行了三种类型模拟中放废液水泥固化体的撞击试验,研究了撞击能量、固化体组份和形状对碎粒尺寸分布的影响,估算了单位撞击能量所增加的表面积(A/E)值。     

The surface tension of liquid silicon at high temperature

The measurement of the surface tension of liquid silicon has a long history with many results but no general agreement between them. Two values at the melting temperature are cited in reviews (749 and 827 mN/m [N. Eustathopoulos, E. Ricci, B. Drevet, Note Technique DEM No. 97/58, CEA, 1997]) but there are few arguments to determine the correct one. In the present study, new data for the surface tension obtained with the analysis of characteristic frequencies of a levitating drop are presented. The effect of oxygen and nitrogen are also considered. These data are compared with former data obtained with contactless techniques. The most recent surface tension values obtained with drop weights ranging on two orders of magnitude and environments of different natures (argon, hydrogen and vacuum) show excellent agreement (within a 1.5% margin) at temperatures between 1350 K and 2400 K. The comparison of these data to others obtained with different techniques, reveal a good agreement, except those obtained with the sessile drop technique on some supports like BN, SiO₂ and MgO. However, these special cases may be connected with the reactivity of silicon with these supports.     

连铸坯微观及宏观偏析数学模型的研究进展

对连铸坯微观和宏观偏析模型及树枝晶间液相流动的研究进展进行了评述，采用近平衡凝固过程溶质再分配理论并结合连铸传热数学模型对连铸坯微观及宏观偏析的定量解析方法进行了分析。     

Numerical simulation of solidification kinetics in A356/SiCp composites for assessment of as-cast particle distribution

The present work is aimed at studying the effect of solidification rate on reinforcement clustering in particle reinforced metal matrix composites (PMMCs) through numerical simulations and experimental studies. A macrotransport-solidification kinetics (MTSK) model was used to simulate the solidification kinetics of the PMMCs. The experimental validation of the numerical model was achieved through the Newtonian and Fourier thermal analysis methods. Results reveal that the MTSK model can be successfully used to predict the local microstructural scales and to evaluate the risk of cluster formation in cast particle reinforced composites.     

Effect of silicon content on microstructure and electrochemical behavior of hypoeutectic Al-Si alloys

The correlation of mechanical properties and corrosion behavior with microstructure parameters can be very useful for planning solidification conditions in order to achieve a desired level of final properties. The present study aims to investigate the influence of silicon content on the microstructural pattern, i.e., dendrite spacings and distribution of interdendritic phases on the corrosion behavior of Al-Si alloys castings. The corrosion resistance was analyzed by both the electrochemical impedance spectroscopy (EIS) technique and Tafel's plots carried out in a 0.5 M NaCl test solution at 25 °C. The increase on silicon content has provided a dendritic refinement and a more extensive redistribution of the eutectic mixture which has provoked a decrease on the corrosion resistance.     

Thermal analysis and solidification pathways of Mg–Al–Ca system alloys

Mg–Al–Ca alloys are creep resistant magnesium alloys with high application potentials. The solidification pathways and microstructure formation in this alloy system are still under discussion. In this paper, the solidification behavior of AZ91 and AM50 with Ca addition (AZC91x and AMC50x alloys) was investigated by a computer-aided cooling curve analysis (CA-CCA) system. Microstructure and phase identification were carried out by SEM and EDX analysis. The results show that the Ca-containing phase formation mainly depends on Ca content and Ca/Al ratio. With increasing the Ca/Al ratio these phases transform from Al₂Ca to (Mg, Al)₂Ca and Mg₂Ca. Moreover, Ca addition decreases the liquidus temperature of Mg–Al alloys, but influences the solidus temperature in a more complex way. Increasing the Ca content also decreases the solid fraction at which dendrite coherency occurs. The relationship between solidification interval, dendrite coherency point, formation of Ca-containing phases and hot tearing is also discussed.     

Effects of growth rate and temperature gradient on the microstructure parameters in the directionally solidified succinonitrile–7.5 wt.% carbon tetrabromide alloy

Succinonitrile (SCN)–7.5 wt.% carbon tetrabromide (CTB) alloy was unidirectionally solidified with a constant growth rate (V = 33 μm/s) at five different temperature gradients (G = 4.1–7.6 K/mm) and with a constant temperature gradient (G = 7.6 K/mm) at five different growth rates (V = 7.2–116.7 μm/s). The primary dendrite arm spacings, secondary dendrite arm spacings, dendrite tip radius and mushy zone depths were measured. Theoretical models for the microstructure parameters have been compared with the experimental observations, and a comparison of our results with the current theoretical models and previous experimental results have also been made.