Effect of welding parameters on the heat-affected zone of AISI409 ferritic stainless steel

One of the main problems during the welding of ferritic stainless steels is severe grain growth within the heat-affected zone （HAZ） In the present study, the microstmctural characteristics of tungsten inert gas （TIG） welded AISI409 ferritic stainless steel were investigated by electron backscattered diffraction （EBSD）, and the effects of welding parameters on the grain size, local misorientation, and low-angle grain boundaries were studied. A 3-D finite element model （FEM） was developed to predict the effects of welding parameters on the holding time of the HAZ above the critical temperature of grain growth. It is found that the base metal is not fully recrystallized. During the welding, complete recrystallization is followed by severe grain growth. A decrease in the number of low-angle grain boundaries is observed within the HAZ. FEM results show that the final state of residual sWains is caused by competition between welding plastic strains and their release by recrystallization. Still, the decisive factor for grain growth is heat input.

烧结温度对生物医用纳米Ti-15Mo合金组织和摩擦学性能的影响（英文）

研究烧结温度(1073~1373 K)对具有纳米结构的球磨β型Ti-15Mo合金结构和摩擦学性能的影响。通过多种技术对试样进行表征,如X射线衍射分析(XRD)、电子扫描电镜(SEM)和球盘式往复摩擦试验机等;采用不同载荷(2、8和16 N)进行磨损试验。结果表明,随着烧结温度的升高,合金的平均孔径和晶粒尺寸不断减小,在1373 K时分别达到最低值:4 nm和29 nm,1373 K烧结样品的相对密度高达97.0%。此外,烧结温度越高,试样的相对密度越大、硬度越高、弹性模量越高;1373 K烧结试样由于其较低的闭孔率导致摩擦因数和磨损率也较低。