低温回火时间对GCr15钢组织演变与力学性能的影响

采用扫描电镜(SEM)、能量色散光谱仪(EDS)、电子背散射衍射(EBSD)技术、X射线衍射(XRD)、万能试验机、洛氏硬度计等研究了低温回火时间对GCr15钢显微组织和力学性能的影响。结果表明:随着回火时间的增加,GCr15钢中碳化物面积分数不断增加,其平均直径先增加后减小;回火态与淬火态的碳化物类型主要为M7C3和M23C6;随着回火时间的增加,试验钢的回火马氏体逐渐分解消失,组织形态有显著变化,但其尺寸变化不大,抗拉强度逐渐升高,但硬度有一定程度降低。

Effects of strain rate on mechanical properties, microstructure and texture of Al-Mg-Si-Cu alloy under tensile loading

The effects of strain rate on the mechanical properties,microstructure and texture of Al-Mg-Si-Cu alloy were investigated through tensile test,microstructure and texture characterization.The results show that strain rate has some influences on the mechanical properties and microstructure,but a slight influence on the texture.Overall,yield strength,ultimate tensile strength and elongation increase first,then remain unchanged,and finally increase with increasing strain rate.Independent of strain rate,microstructure in the vicinities of the fracture regions of all the specimens is composed of the slightly elongated grains.However,some differences in misorientation angle distributions can be observed.As strain rate increases,the low angle grain boundaries(LAGBs)increase first,and then decrease.Textures in the vicinities of the fracture regions are almost identical with increasing strain rate.

过盈量及滚花方式对装配式凸轮轴压装失效的影响

基于有限元仿真方法,研究了过盈量及滚花方式对装配式凸轮轴滚花连接塑性变形及相对滑动等压装失效问题的影响。结果表明:增加连接过盈量能够获得更大的压装力和摩擦剪应力,使连接件配合面越不容易发生相对滑动;另外,过盈量的增加也将导致凸轮轮廓面径向位移数值变大且梯度变化更不均匀,轮廓面过渡区域附近的应力集中明显。为保证配合面不发生打滑,当轴体相对凸轮片较硬时,宜选用轴向滚花连接;反之,则采用横向滚花连接。横向滚花压装试验测得的压装力数据验证了1/36等分压装模型和完整压装模型的合理性。