航空发动机16Ni3CrMoE钢制输出轴的热处理畸变控制

通过对航空发动机16Ni3CrMoE钢制输出轴渗碳淬火后出现轴向长度缩短、内花键畸变的原因进行分析与研究。结果表明,热处理畸变主要影响因素是零件在渗碳、淬火工序中产生的热应力和组织应力的综合作用,渗碳零件表面和心部的成分存在差异,使热处理过程中的应力分布变得更不均匀和复杂。通过改变渗碳装炉方式、降低渗碳冷却速度、静油等温淬火、渗碳前增加稳定化处理等工艺方法,将零件的热处理畸变控制在工艺要求范围内。     

选区激光熔化MnSi2增强316L不锈钢复合材料的表面质量及耐蚀性能

为改善316L不锈钢在海洋环境下的耐腐蚀性能,通过MnSi₂增强316L不锈钢基体,采用选区激光熔化(SLM)制备MnSi₂/316L不锈钢复合材料。利用Image-Pro Plus软件、光学显微镜、扫描电镜(SEM)及电化学工作站研究了激光功率对316L不锈钢金属基复合材料致密度及耐腐蚀性能的影响,通过Tafel极化曲线和阻抗谱表征其耐腐蚀性能的强弱,并通过点蚀形貌揭示了其腐蚀机理。结果表明:添加MnSi₂是提高316L不锈钢耐腐蚀性能的有效途径。随着激光功率的增大,耐腐蚀性能呈现先提高后降低的趋势,当激光功率达到190 W时,2%MnSi₂/316L不锈钢复合材料的致密度为99.80%,其腐蚀电位为－0.053 V (vs SCE)。同时,2%MnSi₂可以显著改善316L不锈钢的成形质量,提高其耐腐蚀性能,其腐蚀形式为氯离子诱导氯化物生成的点蚀,且点蚀产生位置主要集中在孔隙边界处。     

Evolution mechanism of crystallographic orientation in grain continuator bars of a Ni-based single-crystal superalloy prepared by Bridgman technology during directional solidification

Single-crystal rods with different diameters and deviation angles with respect to the solidification direction were produced by Bridgman rapid solidification method at withdrawal rates of 3 and 6 mm·min^-1 and used as grain continuators.The crystallographic orientation of the rods,which cross-sections were perpendicular to the solidification direction at different solidification heights,was measured by electron backscattered diffraction,while the corresponding microstructures were observed by optical microscopy.The mushy zone morphology and the distribution of the temperature gradient were simulated by the finite element analysis software ProCAST.The experimental results indicate that the crystallographic orientation of the single-crystal rods corresponds to the statistical average value of all the dendrite orientations in cross-section.The crystallographic orientation of the primary and secondary dendrites of each single-crystal rod at different cross-sections fluctuates irregularly within a small range(less than 4°).The crystallographic orientation of the dendrite in each single-crystal rod is not exactly consistent with each other and is affected by their branching mode of dendrites in the solidification space.In addition,the simulation results show that the mushy zone shapes and the temperature gradient of single-crystal rods change with the increase of solidification height during the solidification process.Finally,the evolution mechanism of the crystallographic orientations and the corresponding influence factors were analyzed and discussed.     

汽车后尾灯覆盖双色注射模设计

叙述了一种汽车后尾灯覆盖双色注射模的设计方法。系统阐述了该类塑件因结构导致的注射成型后表面窜色缺陷,通过塑件局部调整和模具结构设计解决了此类问题,并以此提升生产效率和模具竞争力。     

Precipitation Behavior and Mechanical Properties of a 16Cr-25Ni Superaustenitic Stainless Steel Weld Metal During Post-weld Heat Treatment

A 16Cr-25Ni superaustenitic stainless steel weld metal for austenitic stainless steel/ferrite heat-resistance steel dissimilar metal weld was designed and prepared through tungsten inert-gas welding. The precipitate evolution and its correlation with mechanical properties were investigated during post-weld heat treatment (PWHT) at 690 °C for up to 12 h. The primary precipitates in the as-welded weld metal were identified as Mo-rich M₆C carbides in the interdendritic region and semicontinuous fine-sized M₂₃C₆ carbides along grain boundary. After PWHT, three types of precipitates coexisted in the interdendritic region: primary M₆C carbides, newly precipitated Mo-rich M₂X carbonitrides and some of the secondary M₂₃C₆ carbides. Additionally, mass secondary M₂₃C₆ carbides formed and coarsened along grain boundary. No undesirable intermetallic phases formed during the whole period. The M₂X and interdendritic M₂₃C₆ improved the strength of the weld metal after PWHT, but the elongation and impact toughness degraded, which were mainly owing to the intergranular M₂₃C₆ carbides that changed the fracture mode from ductile transgranular mode to mixed mode of transgranular and intergranular fracture. Meanwhile, the coarsening of M₂X carbonitrides may lead to the elongation loss during 8 h to 12 h. Evolution of impact toughness was also related to the M₂X carbonitrides, which made the crack easier to propagate compared with austenitic matrix and contributed to the decline of impact toughness. However, due to the sluggish precipitation of M₂X carbonitrides with longer holding time, the decreasing trend became slow from 4 to 12 h. The results showed that PWHT should be controlled within 8 h to obtain better combination of strength and ductility.     

Finished surface morphology,microstructure and magnetic properties of selective laser melted Fe-50wt% Ni permalloy

This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer,optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser(LVED) on structure, and magnetic properties with coercivity ( H _c ), remanence ( B _r ), and power losses ( P     

Surface Structures and Their Relative Stabilities of Orthorhombic YAlO3: A First-Principles Study

First-principles energetics calculations were performed to investigate the structures and relative stabilities of six low millerindex surfaces of orthorhombic YAlO₃(YAP).The stoichiometric YAP (100) and (001) were predicted to have the lowest surface energies of 1.91 and 1.96 J/m ²,respectively.Using a thermodynamic defect model,non-stoichiometric YAP surface energies were further predicted as a function of ■ and temperature (T).All the results were combined to construct th...     

Erosion Behavior of NiCoCrFeNb0.45 Eutectic High-Entropy Alloy in Liquid-Solid Two-Phase Flow

The metal components exposed to the high-velocity liquid-solid ? ow can be rapidly eroded by the accelerated particles.With an excellent combination of strength and toughness, the NiCoCrFeNb _0.45 eutectic high-entropy alloy (EHEA) has emerged as a promising material to resist erosion damage. In this study, the erosion behavior of NiCoCrFeNb _0.45 EHEA in high-velocity multiphase ? ow is investigated through the coupling analysis of material properties, multiphase ? ow, a...