A novel binder and binder extraction method for powder injection molding of tungsten cemented carbide

1　INTRODUCTIONPowderinjectionmolding (PIM ) ,whichisde rivedfromplasticinjectionmolding ,isakindofnet shapepowdermetallurgyformingprocess[13] .Com bininghigh partcomplexitywithhigh productionquantities ,itsupplementstheestablishedprocesseslikediecompaction ,machiningandinvestmentcasting[4 6 ] .Comparingtoconventionalpressing/sinteringprocess,thePIMhasgreattechniqueandcostadvantagesforthepro ductionofcementedcarbidecomponentswithcomplexshapes[7,8] .Sincehydraulicpressureisappliedduringi…     

高强度ZL205A合金大型铸件"白点"偏析研究

对ZL205A合金某大型铸件进行探伤检测,在底片上发现了白色点状偏析组织(以下简称“白点”偏析)。铸造工艺调整以及热处理不能使之减轻或消除。文中对ZL205A合金白点偏析进行研究,测试了偏析组织的力学性能,分析了偏析组织的微观形貌及化学成分,并探讨了其形成机理及防止措施。     

氮化铝陶瓷研究和发展

从氮化铝陶瓷的制备工艺，即粉末的合成、成形、烧结3个方面详细介绍了氮化铝陶瓷的研究状况，指出低成本的粉末制备工艺和氮化铝陶瓷的复合形状成形技术是目前很有价值的氮化铝陶瓷的研究方向。     

Preparation ofAZ91 alloy by powder metallurgy method

Magnesium alloy AZ91 was prepared by powder metallurgy method, and the effect of sintering temperature on the densities and microstructures of the alloys was investigated. The results show that tight control of the sintering temperature within a narrow range around the liquidus level generates structures with high integrity and reduces some of the disadvantages caused by the higher temperatures. The matrix consists of α-Mg grains/cells surrounds by discontinuous precipitates of Mg17Al12 intermetallics which are normally located at the grain boundaries and triple junction.     

Mechanical properties and microstructure of Ti-6Al-4V compacts by metal injection molding

Ti-6Al-4V compacts were fabricated by metal injection molding(MIM). Influence of vacuum sintering time on mechanical properties and microstructure of the sintered compacts at 1 260 ℃ were investigated. The experimental results show that the compacts sintered at 1 260 ℃ for 3 -6 h, which was made from hydrogenation-dehydrogenation(HDH) powder(average particles size is 45 μm), have a relative density of 95.6%- 96.7%, ultimate tensile strength of 648 - 686MPa and 0.2% yield strength of 526 - 615MPa; but a lower elongation(＜4%) and that the compacts sintered at 1 260 ℃ for 2 - 6 h, which was made from 90% gas-atomized powder(average particles size is 32.5 μm) and 10 % HDH powder, have higher relative density(＞95 %), ultimate tensile strength of 800 -848MPa,0.2% yield strength of 712 - 762MPa and high elongation (7.4%- 9.5%). When the sintering time is increased,porosity decreases and microstructure of sintered products changes from equiaxed to typical Widmanstatten, the average sizes of prior β grains, α colonies and α phase thickness in the β grains increase accordingly. After HIP treatment,pores obviously become less, microstructure of alloy is refined and mechanical properties are greatly improved.     

表面处理对磁粉抗氧化性及注射成形粘结磁体的影响

对NdFeB磁粉进行了不同表面处理,研究了表面处理对磁粉抗氧化性、喂料流动性及粘结磁体性能的影响规律.结果表明:(1)NdFeB磁粉经改性处理后,粉末在300℃及500℃的氧化增重率大大降低;而且采用先磷酸后硅烷的复合处理工艺要比单一的硅烷处理或单一的磷酸处理效果更好;(2)KH550硅烷耦联剂能有效地改善NdFeB磁粉与尼龙粘结剂相容性,相应制得的喂料流动性要好于未改性磁粉,而且能相对提高NdFeB磁粉的装载量,使得最大装载量(体积分数)达到67%;(3)通过对磁粉表面改性,改善了磁粉与塑料粘结剂的界面特性,不仅提高了注射成形粘结磁体的磁学及力学性能,而且改善了粘结磁体的耐热性能.     

生物医用多孔钛及钛合金激光快速成形研究进展

多孔钛及钛合金具有良好的生物相容性和与人骨更匹配的力学性能,是人体理想的替代材料,因此其制备技术及相关性能研究引起了广泛关注。激光快速成形是一项先进的制造技术,在制备生物多孔金属材料时具有独特的优势。介绍了激光快速成形的工作原理和技术特征,根据成形工艺特点简要回顾了4种代表性激光快速成形技术(选择性激光烧结、选择性激光熔化、激光近净成形和激光立体成形)的国内外发展现状,并重点论述了这几种技术在制备生物医用多孔钛及钛合金方面的最新研究进展,最后指出了今后在该领域的主要研究工作。     

二硅化钼抗氧化性的研究进展

MoSi2具有良好的高温抗氧化性，但是低温容易发生“粉化瘟疫”现象。首先介绍了MoSi2及其复合材料低温“粉化瘟疫”的现象和机理，提出了预防“粉化瘟疫”的方法，然后介绍了MoSi2基复合材料的高温抗氧化性能以及抗高低温循环氧化的能力。总结认为低温加速氧化是MoSi2的本质现象，而“粉化瘟疫”不是MoSi2的本质现象。     

纳米硬质薄膜的研究进展

介绍了纳米硬质薄膜的概念、设计思想、超硬机制、制备技术及工艺、性能、应用前景，综述了近几年来国内外纳米硬质薄膜材料研究的最新进展，对纳米硬质薄膜的发展趋势提出了一些看法。     

SiCf/SiC复合材料的制备与力学性能

分别采用先驱体裂解-热压和先驱体浸渍-裂解方法制备出了SiCf/SiC复合材料.重点探讨了不同制备工艺对复合材料纤维/基体间界面和断裂行为的影响.研究表明,采用先驱体裂解-热压工艺制备复合材料时,虽然烧结液相可以促进复合材料的致密化,但其同时导致纤维与基体间的界面结合强以及纤维本身性能的退化,因此复合材料表现为脆性断裂,具有较低的力学性能.而采用先驱体浸渍-裂解法制备复合材料时,由于致密化温度较低,复合材料中纤维与基体的界面结合较弱,而且纤维的性能保留率较高,因此,纤维能够较好地发挥补强增韧作用,复合材料具有较好的力学性能,其抗弯强度和断裂韧性分别为703.6MPa和23.1Pa.m1/2.