Cr12MoV模具钢的激光熔覆

利用不同的激光工艺参数对Cr12MoV模具钢表面进行熔覆试验，探讨了熔覆层裂纹和气孔产生的趋势和工艺参数对熔覆层深度的影响，研究了表面微观硬度的分布及其原因、熔覆层耐磨性能的提高幅度以及组织结构的变化。结果表明，采取适当工艺措施，可以完全消除熔覆层的气孔，减少横向裂纹；表面硬度在不同程度上都得到提高，硬度峰值出现在次表层；激光熔覆层的耐磨性能可以提高47％－76％；微观结构是由平面晶和枝晶构成的共晶组织，并有多种合金相分布在枝晶间。     

Effect of austenitization heat treatment on the magnetic properties of Fe-40wt % Ni-2wt % Mn alloy

The effect of austenitization heat treatment on magnetic properties was examined by means of M6ssbauer spectroscopy on an Fe-40wt%Ni-2wt%Mn alloy. The morphology of the alloy was obtained by using scanning electron microscopy （SEM） under different heat treatment conditions. The magnetic behavior of the non heat-treated alloy is ferromagnetic. A mixed magnetic structure including both paramagnetic and ferromagnetic states was obtained at 800℃ after 6 and 12 h heat treatments. In addition, the magnetic structure of the heat-treated alloy at 1150~C for 12 h was ferromagnetic. With the volume fraction changing, the effective hyperfine field of the ferromagnetic austenite phase and isomery shift values were also determined by Mtssbauer spectroscopy.     

Selective etching of habit faces of ferroelectric Ca2Sr(C2H5CO2)6 crystals

Crystallographically oriented etch traces produced by selective etchant on (111) and (110) habit faces of dicalcium strontium propionate [Ca₂Sr(C₂H₅CO₂)₆] crystals are attributed to the growth traces nucleated during the superficial growth of crystal. This view is supported by the absence of such etch traces on seized habit faces and from the observations of layer structure on the bottom faces. Mother liquid acting as an etchant produces circular terraced depressions on habit faces. These depressions originate at the sites of isolated impurity centres. Identical features such as circular etch structures bounded by cylindrical outer periphery produced on cooled faces are attributed to isolated domains.     

工艺因素对球铁中奥氏体枝晶数量和形态的影响

采用着色腐蚀法显示出球墨铸铁中的奥氏体枝晶,研究了碳当量、浇注温度、壁厚及含硅量对球墨铸铁中奥氏体枝晶数量和形态的影响。结果表明：碳当量减少．枝晶数量增多,形态趋于发达;壁厚减小,枝晶数量增多,形态变得发达;浇注温度提高,枝晶数量减少而形态变得粗壮,不发达;含量增加,枝晶数量减少。     

ZL109合金圆柱体铸件凝固期热参数、二次枝晶间距、抗拉强度之间关系的研究

本文针对ZL109合金圆柱体铸件,在砂型铸造条件下,研究了凝固时间τ,温度梯度G,凝固指数fi,真温度梯度加速度GAP与铸件二次枝晶间距DAS,孔洞率戶和极限抗拉强度UTS之间的关系。结果表明:1.τ,fi与DAS的关系最为密切。2.DAS和户都影响铸件的UTS,在本实验条件下,DAS的影响是主要的,P可忽略不计,可以用DAS来评定UTS。3.fi与UTS的关系最为密切,用fi来控制UTS更为有效。此外,还探讨了铸件由表及里DAS的变化及用DAS无损测试铸件UTS的精度。     

模具钢的激光熔覆组织和性能

利用不同的激光工艺参数对Cr12MoV模具钢表面进行熔覆试验,探讨了工艺参数对熔覆层深度的影响,研究了表面微观硬度的趋势及其原因、熔覆层耐磨性能的提高幅度以及组织结构的变化。结果表明：表面硬度在不同程度上都得到提高,硬度峰值出现在次表层;激光熔覆层的耐磨性能可以提高到1．91－4．24倍;微观结构由平面晶和枝晶构成的共晶组织,并有多种合金相分布在枝晶间。     

局部溶质再分配方程的修正

抽象出了两种简单的枝品形态,通过对凝固过程中固液界面传质过程的分析,对Flemings的“局部溶质再分配方程”进行了修正。考虑了固相中的扩散,提出了更为一般的局部济质再分配方程。结合具体的凝固过程,选择恰当的参数,该方程可用于宏观偏析和微观偏析的计算及非平衡凝固条件下第二相和非平衡共晶析出量的估算。     

Ba 变质对亚共晶 Al-Si 合金初生α固溶体的细化作用

用含钡中间合金处理亚共晶Ａｌ－Ｓｉ合金,重点研究Ｂａ元素细化α固溶体的效果和机理。研究表明：当合金中残留含Ｂａ量为０．０５％～０．０８％时,无论是硅晶体还是α固溶体均获得了最佳的变质和细化效果,力学性能也出现了峰值效应。扫描电镜和电子探针结果表明：Ｂａ元素主要吸附在α固溶体的枝晶间和枝晶前沿,因阻碍α固溶体的过快生长和促进枝晶分枝、熔断等而起到了细化作用。