Graphene added multilayer ceramic sandwich (GMCS) composites: Structure,preparation and properties

The multilayer ceramic composites (MLC) consist of two ceramic materials insoluble in each other and sequentially piled in a symmetric manner whereas they can be divided into two groups: multilayer composites with weak interfaces and composites with strong interfaces. The graphene added multilayer ceramic sandwich (GMCS) composite was developed. The multilayer stack of Si₃N₄ with 5 and 30 wt% graphene addition were stratified in sandwich structure. So formed multilayer stacks with 5 and 7 layers were sintered by hot issostatic pressing (HIP). The homogenity of graphene addition, the effect of layered structures and the position of layers with lower and higher graphene content on the final properties were studied.     

涡轮叶轮用铸造高温合金的热等静压处理研究

对涡轮叶轮用铸造高温合金进行热等静压处理。结果表明,通过热等静压处理,铸造高温合金的疏松缺陷减少,显微组织均匀细化,合金致密度提高,而且力学性能得到了改善。     

粉末冶金/热等静压(PMHIP)零件的生产工艺与设计准则

热等静压(HIP)经过几十年发展,现已成为一种用各种金属和/或陶瓷制造形状复杂的、高性能零件的,竞争性制造技术。这些零件现已用于许多对环境要求高的产业部门,例如:航空航天、近海油与气田、能源及医疗等。这篇评述主要讲述关于在金属包套中压制金属粉末的HIP工艺过程,即所谓的PM HIP零件的生产工艺、设计准则及其应用。     

HIP法制备CuCr触头的真空电击穿特性

采用热等静压(HIP)固相烧结法制备了近乎完全致密、低氧、氮含量的CuCr合金材料,研究了在不同烧结温度下制备CuCr合金的Cr相颗粒度、电击穿场强及击穿区域,给出了CuCr合金Cr相粒子半径与击穿场强的关系式。结果表明:随着HIP烧结温度的上升,CuCr触头材料的Cr相颗粒度也将逐渐增大,导致真空电击穿场强减小,与此同时真空电击穿烧蚀面积增大,烧蚀坑深度逐步加深。     

Influence of HIP pressure on tensile properties of a 14Cr ODS ferritic steel

An oxide dispersion strengthened ferritic steel with a nominal composition of Fe–14Cr–2W–0.3Ti–0.3Y₂O₃ (in wt.%) was consolidated by hot isostatic pressing at 1150 °C under various pressures in the range of 185–300 MPa for 3 h. The microstructure, microhardness and high temperature tensile properties of the steel were investigated. With increasing compaction pressure the density of specimens also increased, however OM and SEM observations revealed residual porosity in all tested specimens and similar ferritic microstructure with bimodal-like grains and numerous of large oxide particles, located at the grain boundaries. Mechanical testing revealed that compaction pressure has negligible influence on the hardness and tensile strength of the ODS steel, however improves the material ductility.     

Mechanical alloying and field assisted hot pressing of nanocrystalline B2-NiAl intermetallic compound

Abstract

Ordered B2-NiAl intermetallic compound powder was successfully synthesised by mechanical alloying after 20 h in an attritor mill, starting from elemental Ni and Al powders and without subsequent heat treatment. NiAl powder obtained was homogenous and had a nanocrystalline microstructure. It was consolidated by field assisted hot pressing (FAHP), in a novel configuration with a Gleeble 3800 thermomechanical simulator. The powder was also processed by hot isostatic pressing (HIP) in order to compare both methods. The consolidation was successful by both methods obtaining above 98% of NiAl theoretical density (5·86 g cm^?3). The results showed that the consolidation process by FAHP technique is effective and uniform throughout the sample as indicated by homogenous hardness values, obtaining microstructure and properties similar to those obtained with HIP technique, with certain advantages over it. The achieved room temperature yield strength of 850 MPa and fracture strain 26–28% corresponds to the bulk values of NiAl intermetallic.     

弯曲转子振动特性分析及处理

文章描述了某亚临界汽轮机组高中压转子弯曲发展过程，结合运行参数，分析了转子弯曲的原因是由于热应力造成的，归纳了热应力造成的弯曲转子振动特性，介绍了弯曲转子的处理措施和效果，对后续机组运行监视、转子弯曲原因分析、弯曲转子处理具有一定的借鉴意义。     

纯钒的高温力学性能及断口特征

采用热等静压法制备了纯钒样品,测试了纯钒在700~1100 ℃下的高温力学性能,分析了高温拉伸样品的断口形貌、金相组织。结果表明,随温度的升高,纯钒的强度及韧性均呈下降趋势。700~800 ℃,纯钒具有较好的高温强度及韧性,断口为韧性特征;900~1100 ℃,纯钒的力学性能急剧恶化,断口上出现了大量的解理面及一定的由高温蠕变导致的韧性沿晶,呈现出韧脆断共存的微观形貌;温度升高,解理面有长大趋势。     

Influence of Heat Treatment on the Performance Characteristics of a Plastic Mold Steel

Processing of polymers depends on corrosion‐ and wear resistant tool materials being in direct contact with the feedstock material. Plastic mold steels, a special group of tool steels, are successfully applied here, offering both a good wear and corrosion resistance. The lifetime of tools used for plastic processing not only depends on wear and corrosion resistance but also on the mechanical properties of the tool material for example, its flexural strength. In this work, mechanical tests of a commercial plastic mold steel were performed and related to the heat treatment. A close correlation of the amount of retained austenite and carbides and the mechanical properties was encountered. The paper discusses strategies to optimize the mechanical properties by an adequate heat treatment with regard to the resulting corrosion and wear resistance.     

Effects of pre-sintering and annealing on the optical transmittance of Zr-doped Y2O3 transparent ceramics fabricated by vacuum sintering conjugated with post-hot-isostatic pressing

In this work, Zr-doped Y₂O₃ transparent ceramics were fabricated by vacuum pre-sintering at various temperatures ranging from 1650 to 1800 °C combined with a post-hot-isostatic pressing (HIP) treatment. The pre-sintered samples all show black opaqueness mainly due to the formation of oxygen vacancies, which can be removed by post-annealing in air. The HIP treatment can also eliminate the blackness as well as residual pores, giving rise to optical transparency. The in-line transmittance of the samples after HIP was found to depend strongly on the microstructure of the as-sintered samples. The optimal microstructure of these types of samples before the HIP treatment should be fine grained with only intergranular pores, which can easily be removed by HIP. Annealing before HIP was shown to be necessary to enhance the transmittance of the samples. The effects of the pre-sintering heating rate on the optical transmittance of the HIP-treated samples were also studied.