温压工艺最新进展--流动温压技术

流动温压技术兼有温压技术和金属注射成形技术的优点,既克服了传统粉末冶金技术在成形方面的不足,又避免了注射成形技术的高成本.由于微细粉末的加入和较多的润滑剂含量而使混合粉末在温压时转变成一种具有良好流动性和充填能力的黏流体,从而可以直接成形零件的复杂几何形状如侧凹、螺纹孔等而不需要其后的二次机加工,具有很大的应用潜力.     

磁性材料注射成形技术

概括了金属粉末注射成形技术(MIM)制造粘结永磁和烧结磁体的特点和优点。详细介绍MIM粘结永磁和烧结磁体的基本工艺过程及基本要求。综述了注射成形磁性材料的主要研究与发展方向。最后指出磁性材料注射成形技术的研究意义。     

钨基重合金注射成形工艺研究

研究了三种钨基重合金的金属注射成形工艺（MIM）,重点研究了脱脂和烧结两个工序,分析了烧结温度对力学性能、断口和显微组织的影响。列举了烧结收缩、力学性能和最佳烧结温度等数据。     

Fe-2Ni金属注射成形工艺研究

采用金属粉末注射成形工艺(MIM)制备Fe-2Ni合金。选择了5种石蜡基粘结剂,结果表明,由多组元聚合物组成的粘结剂注射成形性能好,热脱脂后无缺陷,样品形状保持完整。列举最佳工艺参数及烧结合金的机械性能。     

钨基重合金的注射成形工艺

研究了3种钨基重合金的金属注射成形工艺(MIM),重点研究了脱脂和烧结两个工序,分析了烧结温度对机械性能、断口和显微组织的影响,列举了烧结收缩、机械性能和最佳烧结温度等数据。     

Metal injection moulding (MIM) as an alternative fabrication process for the production of TWIP steel

Twinning Induced Plasticity (TWIP) steels are high manganese austenitic steels that have caused growing interest over the last decade due to their unique combination of strength and elongation. Nevertheless, the problems presented during their current fabrication process (continuous casting) complicate their production and commercialisation. Powder metallurgy may be an attractive alternative route of solving these problems in certain components. In this work, Metal Injection Moulding (MIM) is explored as an alternative fabrication method for TWIP steels, having the additional benefit of reaching a near-theoretical densification. The feedstock of this study is composed of a metallic prealloyed Fe–Mn–C–Al–Si powder and a binder system based on wax-HDPE. The feedstock was optimised by examining different metallic loads. A suitable powder–binder ratio was determined based on mixing torque and melt flow index measurements. It was optimised a two-stage debinding process and a sintering process in an argon atmosphere to obtain the correct microstructure.     

注射成形混料流变性的研究

研究了不同粒度、形状的金属粉末与以甲基纤维素基粘结剂组成的注射成形混料的流变性。采用自行设计的毛细管流交仪在MTS880材料试验机上得到混料在10～10~4/s剪切速率范围内的粘度-剪切速率对数关系曲线。探讨了影响流变性的因素和注射成形坯烧结后的力学性能,制得了注射成形零件。阐述了注射成形工艺。     

Thermal property measurements of metal injection moulded Inconel 625 and Inconel 718 using combined thermal analysis techniques

ABSTRACT

The high-temperature thermal properties of powder metallurgy derived superalloys have not been reported in the literature. In this study, the coefficient of thermal expansion (CTE), specific heat and thermal diffusivity of metal injection moulded (MIM) Inconel 625 and Inconel 718 were measured. Measurements of wrought Nickel 200 were also made to verify the methods. These thermal property measurements were made in the range of room temperature to 1000–1200°C using dilatometry, differential scanning calorimetry and laser flash analysis. Thermal conductivity of all three materials was calculated using the measured diffusivity, specific heat and CTE. All the MIM results were compared to published data for the wrought form of these alloys and found to be in close agreement outside of phase transition regions.     

MIM Fe基合金的固溶强化

研究金属粉末注射成形(MIM)铁基合金在强还原性氢气氛烧结条件下的合金化强化效果。结果表明,添加Cu、Ni、Mo等元素能取得显著的固溶强化效果,其中成分为Fe-2Ni-2Cu-0.45Mo的机械性能达到σ_b=483 MPa,σ_s=340 MPa,δ=9％和HRB=83。     

硅在高速钢中的使用原则及含硅高速钢的发展

阐述了硅在高速钢中的影响进规律和作用及使用原则，硅影响二次硬化的△Ｗ判据，分析了比较了硅、钴和铝高速钢中的不同作用，介绍了两种新型的含硅高速钢。     

Large thermal hysteresis NiTi Belleville washer fabricated by metal injection moulding

ABSTRACT

In this work, Ni_49.4Ti_50.6 Belleville washers are prepared by metal injection moulding (MIM). The martensitic transition temperatures and service performance of washers were investigated. The thermal hysteresis has reached 63.1–71.6°C, which is much higher than documented data in binary NiTi alloys. Ti₂Ni and Ni₄Ti₃ phase are observed in XRD patterns, which is responsible for the large thermal hysteresis. In the service tests, the restoring forces are higher than 40?kN, which are sufficient to ensure a tight connection of the fasteners. The loop resistance and high-current test have proved the safety of MIM NiTi Belleville washers compared to traditional steel spring washers, which can meet the challenge in complex outdoor circumstances.     

Evolution of properties of parts during MIM and sintering of recycled oxide particles

Metal injection moulding (MIM) is an established process for high volume production of complex shaped metallic parts using commercially available feedstocks. The characteristics of parts after moulding, debinding, and sintering cannot be simply predictable from raw materials because the properties get altered with the process parameters and the corresponding levels of porosity during processing steps. In this study, physical properties, microstructure, and mechanical properties of the MIM parts have been characterised to understand the evolution of strength during various steps in MIM processing. Feedstocks with different binder loading show a considerable difference in physical as well as mechanical characteristics. During sintering of parts which have solid loading of grinding sludge, simultaneous in situ reduction and densification takes place, whereas only densification occurs in carbonyl iron parts. It is, therefore, possible to make complex shaped parts of different levels of porosity from downgraded shop floor metallic waste.     

表面处理对316L不锈钢粉末注射成型性能的影响

以聚乙二醇/环氧树脂（PEG-EP）为粉末表面改性剂,聚甲醛系树脂（POM）为粘结剂体系,混炼制备316L不锈钢粉末注射成型喂料,并通过硝酸催化脱脂后烧结得到316L烧结样品。通过傅里叶红外光谱仪、扫描电子显微镜、接触角测量仪、旋转流变仪、万能材料试验机、金相显微镜、碳硫分析仪、显微硬度计等研究了PEG-EP对316L不锈钢粉末的包覆效果以及PEG-EP表面处理对316L不锈钢粉末注射成型喂料和烧结样品性能的影响。结果表明,PEG-EP成功包覆在316L粉末表面,改善了316L不锈钢粉末与聚甲醛的界面相容性,提高了喂料流动的性能、生坯的力学性能和烧结样品的力学性能及硬度。当添加PEG-EP质量分数为0.662%、粉末装载量（体积分数）为63%时,316L注射生坯的拉伸强度、断裂伸长率、弯曲强度分别为10.57 MPa、8.38%、21.24 N·(mm²)⁻¹;烧结样品晶粒尺寸为50.8 μm,最大抗拉强度和维氏硬度为688 MPa和HV 151,烧结样品的综合性能最佳。     

Sintering parameters and mechanical properties of injection moulded aluminium powder

Abstract

This paper describes the microstructural and mechanical properties of injection moulded aluminium powder. Gas atomised aluminium powder was injection moulded with wax based binder. The critical powder loading for injection moulding was 62·5 vol.-% for feedstock. Binder debinding was performed in solvent and thermal method. After debinding, the samples were sintered at different temperatures and times in high purity N₂. Metallographic studies were conducted to determine the extent of densification and the corresponding microstructural changes. The results show that gas atomised aluminium powder could be sintered to a maximum 96·2% of theoretical density. Maximum density, tensile strength and hardness were obtained when sintered at 650°C for 60 min.     

纳米晶W-Ni-Fe粉的流变行为和烧结特性

研究了W-Ni-Fe纳米晶粉在注射成形中喂料的流变行为,纳米晶W-Ni-Fe粉采用机械合金化(MA)的方法制备,并将此粉末与蜡基粘结剂混合以形成一种喂料,讨论了MA球磨时间,纳米晶粉末体积和温度对喂料流变性的影响,随球磨时间增加,喂料的粘度以及粘度对剪切速率的敏感性降低,因此,在较长的球磨时间下,这种粉末喂料的流动性和成形性变好,随粉末体积增加,喂料的粘度遵循公式呈非线性增加,此时n=0.68.MA粉末喂料的粘度随温度和剪切速率的变化较小,所以注射温度和注射速度的变化对这种MIM注射坯的质量影响较小,本文也讨论了采用MA制备的W-Ni-Fe纳米粉末的烧结特性,实验结果表明球磨可以导致在液相烧结温度以下合金达到很高的密度,大的晶格畸变、晶粒细化和超饱和固溶体的形成,强化了烧结工艺。