Phase field modeling of dendritic coarsening during isothermal solidification

Dendritic coarsening in Al-2mol%Si alloy during isothermal solidification at 880K was investigated by phase field modeling. Three coarsening mechanisms operate in the alloy: (a) melting of small dendrite arms; (b) coalescence of dendrites near the tips leading to the entrapment of liquid droplets; (c) smoothing of dendrites. Dendrite melting is found to be dominant in the stage of dendritic growth, whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding. The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.     

Zn添加对挤压态Mg-Zn-Ce-Zr合金微观组织及力学性能的影响

通过光学显微镜(OM)、扫描电镜(SEM)、背散射电子衍射(EBSD)和力学性能检测,研究不同Zn含量(0.5%、1.5%和2.0%(质量分数))的Mg-Zn-Ce-Zr合金在温度为350℃,挤压比为9,挤压速率为10 mm/s条件下挤压后的微观组织和力学性能。结果表明:随着Zn含量的增加,铸态下晶间析出相明显增多;挤压后,Zn含量对合金晶粒度的影响不大,但棒材的丝织构随Zn含量增加而增强。由于第二相粒子的强化作用,随Zn含量增加,合金的拉伸屈服强度从158 MPa增加到192 MPa,而抗拉强度从219 MPa提高到246 MPa。由于丝织构强度增加,合金塑性随Zn含量增加从33%降低至18%,添加0.5%Zn合金的伸长率和拉压对称性最好。     

Laser welding of 6061 aluminum alloy sheet with surfactant

Aluminum alloy shows low absorption to laser for its essential high reflection property.In this paper,an active laser welding process is adopted to weld 6061 aluminum alloy with the halide surfactant c...     

铜合金水表外壳破裂失效检测分析

采用金相显微镜、扫描电子显微镜、能谱分析仪等检测分析方法对铜合金自来水表外壳在使用中发生破断开裂泄露的原因进行了分析。结果认为,铜合金自来水表外壳在使用中发生破裂属于应力腐蚀破裂,导致发生应力腐蚀的原因与使用环境中的硫化物有关。     

锌铁合金电镀层的油光黑亮钝化工艺

介绍锌铁合金电镀层的黑钝化工艺,分析影响钝化质量的诸因素,指出钝化膜耐蚀性能优异之所在。     

Use of the gold markers method to predict the mechanisms of iron atmospheric corrosion

Iron corrosion under atmospheric conditions has been investigated by using the gold markers method. The corrosion experiments were performed in a climatic chamber with an accelerated treatment. The gold markers localization, carried out by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, revealed that the rust layer growth was essentially due to an internal development. Moreover, microRaman mappings allowed prediction of the mechanism of rust layer evolution during the ageing treatment. Finally these results were compared to samples corroded for several 100 years in order to extrapolate our observations to long term corrosion.     

难加工材料复合振动挤压攻丝工艺及设备研究

根据钛合金的性能,分析了钛合金攻丝的难加工性及挤压攻丝代替切削攻丝的可行性,并在此基础上研制了适应于难加工材料小螺纹攻丝的复合振动挤压攻丝机。新型振动攻丝机采用数控技术,实现了攻丝靠模通用化,具有周向和轴向振动功能,满足振动挤压攻丝新工艺的要求。     

KFC铜合金引线框架带材的连续挤压制造技术

针对目前KFC铜合金引线框架带材主要生产方法中存在的生产工艺流程长、设备投资大、产品成品率低和成本高等问题,提出KFC铜合金引线框架带材的连续挤压制造技术,并通过企业的生产运行,验证了该方法的技术可行性和工艺可行性,使企业的产品生产效率、质量和品种等多方面水平得到提高,尤其具有良好的节能减排优势.     

铝合金地铁车辆系统动力学特性仿真

地铁车辆系统要求具有良好的动力特性。运用多体系统动力学分析软件ADAMS/Rail建立了铝合金A型地铁动车系统动力学分析模型,进行了稳定性、平稳性和曲线通过能力仿真计算,依据相关标准比较全面地分析其动力学特性。结果表明,该车蛇行运动临界速度远大于车辆设计速度,并且其平稳性和曲线通过能力良好,可满足运行要求。