Microstructure and mechanical properties of Fe-doped NiAl-28Cr-6Mo eutectic alloys

Room temperature and high temperature microstructural and mechanical properties of arc melted Ni Al-28Cr-6Mo eutectic alloys doped with 0.1% Fe, 0.2% Fe and 0.5% Fe(mole fraction) were investigated. The homogenization heat treatment of the alloys was conducted at 1300℃ in Ar atmosphere. Microscopic analyses, hardness measurements, XRD measurements and compression tests were used to characterize the alloys. As-cast and homogenized alloys exhibit fine cellular eutectic structures with coarse intercellular eutectic structure. The increase in the content of Fe results in coarsening eutectic layers and the decrease in eutectic cells. All alloys have very high compressive stress and strain at room temperature. The addition of Fe has small negative impact on the strength and ductility of the alloys at room temperature. However, the addition of Fe increases the high temperature strength of the alloy. High temperature XRD patterns show that peaks shift to lower Bragg angles. This indicates that the lattice parameter of the alloys increases.

First-principles and experimental investigations on ductility/brittleness of intermetallic compounds and joint properties in steel/aluminum laser welding

Morphology,distribution,composition,forming ability,structural stability and intrinsic mechanical properties of the intermetallic compounds(IMCs)formed in steel/aluminum laser welding were determined through scanning electron microscope,energy dispersive spectrometer,X-ray diffractometer and first-principles calculation.It was found that the mechanical properties of the joint are limited by the Fe−Al IMCs,whose brittleness is attributed to the orbital hybridization between Al(s),Al(p)and Fe(d).However,the joint properties are improved by adding interlayer,which is ascribed to some changes of electronic structure of the generated IMCs.The transition mechanism of IMCs changing from brittle to ductile is mainly due to the weak ability of interlayer elements to attract electrons.The mechanical properties of the joint are closely related to the ductility or brittleness of the IMCs.Moreover,the addition of Ti foil interlayer effectively improves the mechanical properties of the joints,which means that the experimental verification is in good agreement with the theoretical calculation predictions.

泥质岩盖层前期名义固结压力及封闭特性研究

在油气勘探实践中逐渐认识到,仅仅研究盖层当前封闭性能是不够的,还要研究盖层在地质历史中的演化特征及应力状态与脆性–延性匹配关系,从而为盖层封闭的有效性做出评价。以鄂西–渝东地区的不同地质历史及成岩演化程度的泥质岩盖层为研究对象,采用厚壁钢制容器对试样的径向进行约束来模拟单轴应变试验,根据厚壁圆筒理论建立侧向压力和竖向压力之间的关系,获得其前期名义固结压力;并在此基础上,研究前期名义固结压力与单轴抗压强度、声波波速、孔隙率以及黏土矿物含量等因素的关系以及侧压系数的变化规律;初步探讨泥质岩脆性–延性转化特征及相应封闭临界条件,并对几类泥质岩在各种地质条件下封闭能力给出评级。研究对评价不同演化程度泥质岩盖层的封闭性具有重要的指导意义,为下一步建立盖层动–静封闭评价模型奠定基础。