强磁场对Al-Cu合金凝固组织及溶质分布的影响

对亚共晶Al-10.5%Cu(质量分数)合金进行了均恒强磁场和梯度强磁场下的凝固实验,考察了强磁场对凝固组织形貌及α-Al晶粒内溶质含量的影响.实验结果表明,施加均恒强磁场和梯度强磁场后,组织形貌变化不明显,而α-Al晶粒内溶质含量有所增加.分析认为,这是因为强磁场下的洛仑兹力抑制了凝固过程中固液界面处的Cu原子向液相内的迁移,从而提高了溶质元素在α-Al晶粒内的含量.改变梯度强磁场的方向,α-Al晶粒内溶质含量无明显变化.     

Centerline Segregation in Continuous Casting Billets

Centerline segregation is of practical significance since it affects the material properties. Centerline segregation in continuous casting billets was studied by solving the fluid flow, solidification, and solute transport equations from the initially liquid steel to the completely solid state using the finite difference method with the SIMPLER algorithm. The results show that the centerline segregation is induced by both the fluid flow in the mushy zone and the accumulation of solute-rich liquid near the solidification front. The species concentration in the center of the strand rises quickly in the mushy region to a maximum at the end of solidification. The most serious segregation occurs along the billet centerline.     

注浆凝固掘进技术的应用与实践

煤与瓦斯突出时所产生的强大冲击力，会使采掘工作面的煤（岩）壁及围岩和巷道设施遭到严重破坏，并形成某种特殊形状的孔洞。由于煤与瓦斯突出破坏了巷道煤（岩）原始应力状态与煤岩层结构，工程地质状况恶化。如何安全、经济地通过煤与瓦斯突出孔洞？特别是特大型煤与瓦斯突出孔洞，在煤矿采掘工程上是值得探讨、研究的重要课题。     

高碳钢小方坯的一次枝晶臂间距的影响因素

高碳钢小方坯显微凝固组织的研究表明:一次枝晶臂在凝固过程中不断粗化变短;碳含量高,容易形成长宽比小的一次枝晶,并且一次枝晶臂间距增宽,容易形成粗大的柱状晶组织;过热度高,易形成粗大的一次枝晶,一次枝晶臂间距增宽;拉速慢,容易形成细长的一次枝晶,一次枝晶臂间距减少;二次冷却水流量比增加,易形成细长的一次枝晶,一次枝晶臂间距降低.结晶器电磁搅拌可显著降低一次枝晶臂长宽比,并减小一次枝晶臂间距;搅拌电流增加,则一次枝晶臂间距减小效果更明显.     

Sn—Pb合金的三次树枝晶生长

在定向凝固的条件下对Ｓｎ－Ｐｂ合金的三次树枝晶生长进行了研究。探讨纵向和横向生长的三次树枝晶形态，给出了三次枝晶间距与工艺参数即温度梯度和生长速度之间的指数衰减关系。发现纵向和横向三次枝晶在枝晶粗化和间距上存在着明显的差别，并探讨了枝晶爬行对枝晶不对称生长的影响。     

Study on one—dimensional consolidation of saturated soil with semi—pervious boundaries and under cyclic loading

The variation opf effective stress ratio of stratfied soil with semi-pervious boundaries and under cylic loading was analyzed on the basis of Terzaghi‘s one-dimensional consolidation assumptions.A solution by Laplace Transform was obtained for the case whe the soil was under time-varied loading.With numerical in version of Laplace Tranform.Some useful results were obtained for several kinds of commonly encountered loadings.The results can be meaningful in engineering preactice.     

Consolidation behavior of cement—and lime／cement—mixed column foundations

The consolidation behavior of mixed in place cement-and lime /cement-mixed column was studies.COnsolidation of the composite foundation was modeled as a three-dimensional axi-symmetric problem.The authors used the finite difference method to obtain the pore pressure variation with time at and location below the surface.A computer program developed by the authors was used to draw some interesting conclusions about the consolidation behaviors of cement-mixed pile foundation.Finally,a combined model including the permeability coefficients of cement-mixed piles and soil,was studied and its feasibility was evaluated.     

应用均衡凝固理论实现铜渣模无冒口铸造

铸件的凝固收缩形式不仅取决于材质种类 ,而且铸件结构也对其产生直接影响 ,甚至可以改变其收缩特性[1,7] .通过分析铜渣模产品工艺结构及工艺特征参数 ,为避免传统工艺方法中产生的工艺出品率低、废品率高 ,工艺参数在实际生产中难以控制及铸件清理劳动效率低等缺点、难点 ,改进造型及浇注过程中关键工艺参数 ,实现铜渣模无专设冒口铸造生产 .     

淘汰微机再利用的一个实例

随着计算机技术的发展 ,计算机更新换代很快 ,每个学校都有被淘汰下来的微机设备 ,怎样处理好这些设备 ,是值得探讨的。本文给出了一个变废为宝、废旧利用的实例 ,用 APPLE机做“萘的熔解和凝固过程”实验