铝基钨酸锆复合材料的压力浸渗制备与性能

ZrW2O8化合物在0.3~1 050 K温度范围内都表现出大幅度的各向同性负膨胀特征,因而受到人们的广泛关注。先用共沉淀法合成ZrW2O8化合物前驱体粉末,再经低温热处理以及1 200℃、2 h复合成高纯度的ZrW2O8化合物,最后用压力熔体浸渗法制备成ZrW2O8/6013Al复合材料。经过X射线衍射分析、金相组织观察与分析以及热膨胀仪检测,发现该复合材料有致密度高、ZrW2O8体积分数大(80%)、膨胀系数低(3×10-6/K)等优点,与铝合金材料(热膨胀系数为23.4×10-6K-1)相比,其热学性能大大改善,具有很好的应用前景。     

Ni—Cr／hBN自润滑复合材料的摩擦学性能研究

采用粉末冶金技术制备Ni—Cr／hBN自润滑复合材料,研究hBN含量及摩擦栽荷对Ni—Cr／hBN复合材料的性能及摩擦磨损行为的影响．结果表明：随hBN含量增大,Ni—Cr／hBN复合材料的密度、抗弯强度和摩擦系数均逐渐减小．当载荷为20N时,Ni—Cr／hBN复合材料的磨损速率随hBN含量的增大而减小：当栽荷为60N和100N时,磨损速率随hBN含量增大呈先减小后增大的趋势．当hBN含量不变时。磨损速率随载荷增大而逐渐增大．通过探讨Ni—C汕BN自润滑复合材料的润滑与磨损机理可知。材料的摩擦系数取决于hBN的含量,而磨损速率与材料的力学性能有关．当hBN含量为9％（质量分数）,摩擦载荷为60N时,Ni—Cr／hBN自润滑复合材料具有最佳的摩擦学综合性能．     

Tribological properties of aluminum alloy matrix TiB2 composite prepared by in situ processing

An investigation of the wear behavior, in lubricated sliding and rolling of in situ prepared TiB₂ particle-reinforced 2024 T4 Al alloy matrix composites against 52100 steel and hardened pearlitic nodular cast iron, respectively, was undertaken. In sliding contact, the 10 vol pct 0.3-μm TiB₂-metal matrix composite (MMC) showed slightly less wear than the 10 vol pct 1.3-μm TiB₂-MMC. Transmission electron microscopy of cross sections, taken normal to the wear track and parallel to the sliding direction, revealed that the TiB₂ particles on the wear track were polished and particle pullout was largely absent. This was attributed to the strong interfacial bonding between the Al-alloy matrix and the TiB₂ reinforcing phase. The TiB₂ particles on the wear track inhibited spalling. Subsurface damage of the MMC did not occur. The wear of the steel mating surfaces worn against the TiB₂-MMCs was minor and caused by the cutting action of the TiB₂ particles that resided on the MMC wear track. In rolling contact, the 0.3-μm-size TiB₂-MMC showed 5 times higher weight loss than the 1.3-μm TiB₂-MMC for the same content of reinforcement, but the weight loss of the cast iron mating surface was less for the former. For the smaller particle size, the wear of 5 and 10 vol pct TiB₂-MMCs was the same. A high density of surface cracks was present on the wear track of the 0.3-μm TiB₂-MMC but not on the 1.3-μm MMC. The significance of strong particle/matrix interfacial bonding and particle size effect on the wear behavior of ceramic particulate-reinforced MMCs in lubricated sliding and rolling wear is discussed.     

Microstructure and properties of In situ Al/TiB2 composite fabricated by in-melt reaction method

A novel in situ reaction process-in-melt reaction method was developed. TiB₂ particles form in situ through the reaction of TiO₂, H₃BO₃, and Na₃AlF₆ in an aluminum alloy melt. The results showed that the in situ TiB₂ particles formed were spherical in shape and had an average diameter of about 0.93 μm. Moreover, the distribution of TiB₂ particles in the matrix was uniform. The interface between the TiB₂ particles and the matrix showed good cohesion. The tensile strength and the yield strength of the composite increase with increasing TiB₂ content. When TiB₂ particle content in the matrix was 10 vol pct, the tensile strength, yield strength, and elongation of Al-4.5Cu/TiB₂ composite were 417 MPa, 317 MPa, and 3.3 pct, respectively.     

放电等离子体烧结制备AlN/Al复合材料

AlN/Al复合材料是一种高导热复合材料,但现有制备工艺较为复杂.本文采用高能球磨的方式制备混合粉末,随后采用放电等离子烧结方法成功制备出AlN-20%Al材料.测试结果表明:制备的AlN/Al复合材料的相对密度大于97%,热导率为52.8W/m·K,烧结温度与传统的AlN相比降低了约200℃.     

Healing of a void in a sintered refractory-phase/liquid-metal composite

Conclusions Investigations have established that stable pores can exist in sintered WC-Ni hard metals. The equilibrium pore radius of a WC-Ni composite depends on the amount of the liquid phase and the size of the carbide particles.Translated from Poroshkovaya Metallurgiya, No. 5(197), pp. 44–47, May, 1979.     

Effect of boron on microstructure and mechanical properties of PM sintered and nitrided steels

Abstract

PM Distaloy and Astaloy alloys have many applications in the automotive industry and are used in structural elements with different wear resistance values. Their main features are adequate density, hardness, tensile strength, and good ductility. For the purpose of the experiment presented here, Distaloy SA and Astaloy Mo powders, alloyed with various amounts of elemental boron powder, were used. The Distaloy and Astaloy alloys were produced through mixing, compacting, and sintering at t=1393 and 1473 K, and, after the completed sintering process, they were plasma nitrided at 793 K. Experimental results showed that if boron was added, while sintering, the shrinkage phenomena increased ( 1473 K) and some parameters of those alloys (density, hardness, and tensile strength) were improved. Upon the ion nitriding treatment of the surface of base Astaloy Mo samples, a surface layer was created composed of the ε solution and γ' nitride, whereas the surface layer on the Distaloy SA base was mainly composed of a γ' compound. Boron activates the sintering process of Distaloy SA and Astaloy Mo samples but it has no significant impact on the surface layer's thickness of Distaloy SA alloys as opposed to Astaloy Mo alloys in which boron promotes a greater thickness of surface layers along with a reduced depth of nitrogen diffusion.     

SiCp/Fe复合材料电流烧结工艺及性能研究

研究了一种电流加热动态热压烧结工艺,并研制了相应的设备.采用此工艺对颗粒增强铁基复合材料进行了制备研究.比较了普通粉末冶金和此工艺所制备的SiCp/Fe复合材料的性能以及此工艺中模具的不同对材料性能的影响,结合显微组织观察对此工艺的烧结机理进行了讨论.结果表明:采用陶瓷模具进行电流动态热压烧结,对材料性能提高显著,能在短时间内制备出满足实际应用要求的铁基复合材料,材料组织细小均匀.     

Study on Quantification of Oxide Phases in Ex-situ AlN/Al Metal Matrix Nanocomposites

Al based metal matrix nanocomposite (MMNC) is synthesized by dispersing nanocrystalline aluminium nitride (AlN) particles in Aluminum matrix using ex-situ melt metallurgy method. The entrapment of atmospheric oxygen along with ex-situ particulate has been a long standing issue during fabrication of metal matrix composites. In the present investigation, presence of oxygen has been quantified in synthesized Al-AlN MMNCs with varying AlN content. The high resolution scanning electron microscopy is used to study morphology and distribution of AlN in Al matrix. Energy dispersive spectroscopy analysis is used to quantify in situ oxide phases along with AlN particles in the synthesized MMNCs using thermodynamic mass balance calculations. Present study also attempts to understand the role of in-situ oxide phases on the mechanical properties of MMNCs using microindentation hardness and nanoindentation test.     

The bauschinger effect in a SiC/Al composite

An interesting mechanical property of SiC/Al composites is that the tensile yield stress is less than the compressive yield stress, even though the apparent modulus in tension is greater than that in compression. An investigation was undertaken to determine if the Bauschinger effect (BE) in a SiC/Al composite is asymmetrical. It was found that the BE is indeed asymmetrical in the case of the composite and the magnitude of the BE increases with total forward strain. These results can be explained in terms of the changes in “back stress” caused by the changes in the residual stress and the work hardening during forward strain.     

Tribological behaviour of silver based self-lubricating composite

Abstract

Silver based composites with varying concentration of graphite and/or MoS₂ were prepared by powder metallurgy method. Impacts of composition on the tribological performance of the composites in ambient air and vacuum were investigated. The lowest friction in air was achieved by Ag–20G (vol.-%) composite, while Ag–20MoS₂ exhibited the best lubricity in vacuum. XPS evaluation revealed the oxidation of MoS₂ in air and a decrease concentration of graphite on the surface of the wear tracks under vacuum. As the proportion of graphite to MoS₂ increased, the friction coefficient and the wear rates ascended gradually in air while decreased sharply under vacuum. As compared with other compositions, Ag–15MoS₂–5G exhibited a comparable stable and good tribological performance as the environmental condition changed for its friction coefficient and wear rate remained around 0·14 and 5×10^?6 mm³ N^?1 m^?1.     

纳米石墨/铝-硅-镁复合材料的制备

由于铝和碳几乎不润湿，采用热压方法制备纳米石墨／铝基复合材料，并对样品进行热挤压以减少孔隙。金相显微分析表明纳米石墨的添加量为1％（质量分数）时分散性较好，X射线衍射分析结果显示制备过程中有Mg2Si强化相生成。初步研究结果表明，添加纳米石墨后复合材料的阻尼性能有明显提高。     

Ti/Al/TiN体系自蔓延高温合成钛铝氮复合材料

以Ti,Al和TiN粉体为原料,采用自蔓延高温合成技术制备Ti_2AlN材料,研究原料配比对反应合成Ti_2AlN的影响,并分析Ti_2AlN的形成机制。结果表明:Ti/Al/TiN体系自蔓延高温合成产物主要由TiN,Al_3Ti和Ti_2AlN组成。原料中适当添加过量的Al或Ti,均可显著促进Ti_2AlN的合成,其中添加过量Ti对促进Ti_2AlN合成的作用更明显。而降低TiN的用量对促进Ti_2Al N合成的作用最明显,可获得高Ti_2AlN含量的钛铝氮材料。自蔓延高温合成Ti_2AlN的反应机制为Ti和Al反应合成Ti-Al化合物,同时形成Ti-Al液相;然后Ti-Al液相包裹住TiN晶粒;最后以TiN晶粒为核心,TiN晶粒逐渐与周围的Ti-Al液相反应合成板条状Ti_2AlN。     

原位还原法制备Al/Al2O3复合材料的力学性质及反应动力学

以石英为先驱体,以液态铝为还原剂,在1073～1523 K的温度范围内对原位生成铝/氧化铝复合材料进行了研究,对获得的复合材料的物理和机械性能做了测定,并对材料显微结构进行了观测和分析.在1473K制备的铝/氧化铝复合材料密度为2.95g/cm3,最大弹性模量为130 GPa,最大三点抗弯强度为580 MPa,最大拉伸强度为268 MPa,洛氏硬度为86.产物铝/氧化铝复合材料的形状与作为先驱体的二氧化硅的形状几乎一致.讨论了反应过程的动力学.     

Damage mechanisms in a cast ductile iron and a Al2O3p /Al composite

Mechanical behavior and damage mechanisms of an Al₂O₃ particulate-reinforced Al matrix composite (Al₂O_3p /Al) prepared by pressure infiltration are investigated and compared with those of a cast ductile iron. In addition to low cost and reduced weight, the composite has a Young’s modulus comparable to the ductile iron. However, its fracture toughness is lower than that of the ductile iron. Interface debonding between the graphite and ferrite is responsible for the crack initiation behavior of the ductile iron. The crack in the ductile iron is arrested by the ductile ferrite phase surrounding the graphite, leading to high fracture toughness. For the Al₂O_3p /Al composite, the dominating crack initiation mode is particulate cracking. Interface debonding and zigzag cracking of particulates are additional fracture modes. The high content of Al₂O₃ particulates and the high thermal and elastic incompatibilities between the Al matrix and Al₂O₃ particulates result in brittle fracture and low fracture toughness for the composite. Possible ways to increase the fracture toughness of the Al₂O_3p /Al composite material are also outlined.     

油润滑下Al/MoSi2材料的摩擦学特性

运用M-200型磨损试验机测定了油润滑下Al/MoSi2材料的摩擦磨损性能，采用SEM和X射线观察与分析了摩擦副表面的形貌和相组成，探讨了磨损机制。结果表明：采用20#机油润滑可有效地提高Al/MoSi2材料的摩察磨损综合性能；与干摩擦状态相比，其摩擦系统和磨损率分别下降了40%和60%；油润滑时，Al/MoSi2材料的磨损机制主要表现为疲劳点蚀和磨粒磨损。