Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料摩擦磨损性能

将Al2O3-TiC陶瓷材料与具有固体润滑特性的Al2O3-TiC-CaF2陶瓷材料进行叠层,通过真空热压烧结制备Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料.在环盘式摩擦磨损试验机上进行摩擦磨损实验,研究该材料在不同载荷、转速条件下的摩擦系数和磨损率,分别用SEM及EDS观察材料磨损前后的微观形貌和分析其成分组成,研究其磨损机制.结果表明:在相同载荷条件下,Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料的摩擦系数和磨损率随着转速的升高而下降,在相同转速条件下,其摩擦系数和磨损率随着载荷的增加而下降;Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料的磨损机制主要是磨粒磨损和黏着磨损.     

Friction and wear behaviors of B4C/6061Al composite

The friction and wear behaviors of B₄C/6061Al composite were studied by considering the effect of sliding time, applied load, sliding velocity and heat treatment. The results show that, when the sliding time, applied load and sliding velocity reach critical values (namely 120 min, 30 N and 240 r min⁻¹, respectively), the mass loss and friction coefficient (COF) increase significantly. Severe delamination wear is the main wear mechanism after sliding for 120 min and under an applied load of 30 N. While fretting wear happens at a sliding velocity of 240 r min⁻¹. After solution-treated at 550 °C for 1 h and then aged at 180 °C for 15 h, the composite shows the highest wear resistance owing to the precipitation of β″ (Mg₂Si) phases in the matrix and the strong interface bonding between B₄C particles and the matrix alloy.     

Deformation behaviour and microstructure of a 20% Al2O3 reinforced 6061 Al composite

Deformation and microstructural behaviours of a 20% (volume percent) particle reinforced 6061 Al matrix composite have been studied by torsion from 25 to 540°C with strain rates of 0.1, 1 and 5 s⁻¹. The logarithmic stress versus reciprocal temperature relationship exhibits two slopes indicating different deformation mechanisms. The 20% Al₂O₃/6061 Al composite shows a greater hardening behaviour than those of the 10% Al₂O₃/6061 Al composite and of the monolithic alloy. Above 250°C, TEM investigations reveal much smaller subgrain size and higher volume of non-cellular substructures, as well as dynamic recrystallization nuclei in the 20% Al₂O₃/6061 Al composite in comparison to those of the 10% Al₂O₃/6061 Al composite and matrix alloy the same test condition. The torsion fracture surface was studied and compared to the three point bending failure specimens.     

扩散焊条件下Al2O3P/6061Al复合材料中氧化膜的行为

研究了Ａｌ２Ｏ３ｐ／６０６１Ａｌ铝基复合材料扩散焊接头区域氧化膜随焊接温度变化的规律,分析了氧化膜的变化机理,探讨了氧化膜对接头强度的影响。结果表明,在扩散焊时,随焊接规范的变化Ａｌ２Ｏ３ｐ／６０６１Ａｌ铝基复合材料接头区域的氧化膜含量及形态有明显的改变,这与Ｍｇ＋４／３Ａｌ２Ｏ３→Ａｌ２ＭｇＯ４＋２／３Ａｌ反应有关,氧化膜的变化直接影响着焊缝的接头强度。     

Superplasticity in an aluminum alloy 6061/Al(2)O(3)p composite

The superplasticity of an Al(2)O(3)p/6061Al composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special thermomechanical processing or hot rolling, simple hot extrusion has been employed to obtain a fine grained structure before superplastic testing. Superplastic tensile tests were performed at strain rates ranging from 10(-2) to 10(-4) s(-1) and at temperatures from 833 to 893 K. A maximum elongation of 200% was achieved at a temperature of 853 K and an initial strain rate of 1.67x10(-3) s(-1). The highest value obtained for the strain rate sensitivity index (m) was 0.32. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took place entirely in the solid state.     

Fatigue damage development in Al2O3/Al composite

Fatigue damage development in two aluminium matrix (Al7SiO.6Mg and Al5Si-3Cu1Mg) composites reinforced with discontinuous Al₂O₃ fibres has been monitored by means of acoustic emission (AE). The AE signals (RMS) recorded during the tests clearly exhibit three distinct stages which correspond to crack initiation, dominant crack formation and stable propagation. Generally speaking, the cracks initiated at a high load level form close together and a dominant crack forms easily. By contrast, at a low load, initiated cracks are widely separated and the formation of a dominant crack is difficult. If there are large defects in the composite, the first stage is absent, even at low load. In the first stage, little change in microstructure and modulus of the composite is observed; in the second, fibre fracture, interface debonding and matrix cracking occur and there are often sinusoidal cracks in the matrix; in the last stage, the principal characteristic is stable propagation of the dominant crack. The degradation of the elastic modulus of the composite in the last two stages is small.     

Mo2Ni3Si/NiSi复合材料涂层的滑动磨损行为

以Mo-Ni-Si合金粉末为原料，使用激光熔敷技术在1Crl8Ni9Ti不锈钢基材表面制备出Mo2Ni3Si／NiSi金属硅化物复合材料涂层．应用OM，SEM，EDS和XRD方法分析了涂层的显微组织．Mo2Ni3Si／NiSi复合材料涂层由初生的Mo2Ni3Si三元金属硅化物树枝晶和枝晶间的Mo2Ni3Si／NiSi共晶组织组成．在常温和高温滑动磨损条件下测试了涂层的耐磨性能．在常温滑动磨损条件下，Mo2Ni3Si／NiSi金属硅化物复合材料涂层的质量损失随着载荷的增加缓慢增加；在高温滑动磨损条件下，Mo2Ni3Si／NiSi金属硅化物复合材料涂层的质量损失随着温度的升高缓慢下降．     

(Al 2O3)P/6061Al的变形断裂特征和塑性

为了更清楚地认识颗粒增强铝塑性差的细微观机制,进行了(A12O3)p/6061Al的拉伸和三点弯曲变形实验,并用扫描电镜观察了变形与断裂的细微观特征.发现:(1)在加载过程中,总是基体先发生变形局部化,形成变形带;变形带内较大的A12O3颗粒优先开裂,形成颗粒尺度的微裂纹;变形带内的集中变形和Al2O3颗粒的继续开裂交互作用,导致微裂纹沿着变形带连接与扩展进而发生宏观低塑性断裂;(2)加载方式、材料状态和变形温度对上述过程没有本质影响.根据以上观察结果和颗粒增强铝的强化机理,讨论了塑性差的细微观机制以及材料状态和变形温度对(Al2O3)p/6061Al塑性的影响.     

温度对Al2O3/ZrB2/ZrO2复合材料摩擦磨损特性的影响

采用UMT-2多功能摩擦实验机,研究了温度对Al2O3/ZrB2/ZrO2复合刀具材料摩擦磨损性能的影响,并分别使用白光干涉仪和扫描电镜分析实验后磨痕的轮廓和微观形貌。结果表明,常温摩擦时,随着ZrB2/ZrO2含量的增加,AZ系列自润滑陶瓷材料与硬质合金对摩时的摩擦系数逐渐降低。高温摩擦时,随着环境温度的提高,表面摩擦温度不断上升,生成的润滑膜有助于使摩擦系数和磨损率下降。     

Preparation and mechanical properties of high-purity Al2O3 fibre/Al2O3 matrix composite

Al₂O₃ matrix composites with unidirectionally oriented high-purity Al₂O₃ fibre with and without carbon coating, were fabricated by the filament-winding method, followed by hot-pressing at 1573–1773 K. The composite with non-coated Al₂O₃ fibre exhibited a bending strength (594 MPa) comparable to that of monolithic Al₂O₃ (589 MPa). While the composite with a carbon-coated fibre had lower strength (477 MPa), it showed improved fracture toughness (6.5 MPa m^1/2) compared to the composite with an uncoated fibre (4.5 MPa m^1/2) and monolithic Al₂O₃ (5.5 MPa m^1/2). This toughness enhancement was explained based on the increased crack extension resistance caused by the fibre pull-out observed by SEM at the notch tip. This revised version was published online in November 2006 with corrections to the Cover Date.     

Al2O3/DLC复合膜摩擦磨损性能的研究

为了提高铝合金零部件的摩擦磨损性能,采用微弧氧化和磁过滤阴极真空弧技术,在其表面制备了Al2O3/DLC复合膜.用X射线衍射分析(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)、原子力显微镜(AFM)以及摩擦试验对复合膜的化学成分、结构、表面形貌及其对铝合金摩擦磨损性能的影响进行了研究.结果表明,在铝合金表面形成了120 μm厚的多孔Al2O3陶瓷膜,与基体结合紧密.外层0.1.μm厚的DLC不改变膜的表面形貌,但是降低摩擦因素,并且进一步提高膜的耐磨性.Al2O3/DLC复合膜为铝合金作为耐磨工件使用提供了很好的承载支持,并且使铝合金表面摩擦磨损性能大大提高.     

Al2O3/Al复合材料的界面结构特征

利用高分辩透射电子显微镜研究挤压铸造法制备的亚微米 Al 2O 3颗粒增强 Al 基复合材料的界面微观结构。结果表明 : Al基体的 (200) 和 (111) 面优先沿 Al 2O 3颗粒表面生长 , 在复合材料界面处 Al 基体与 Al 2O 3颗粒具有 Al (200) ∥Al 2O 3 (101 2) 、Al [011 ] ∥Al 2O 3 [0221 ] 的晶体学位向关系并形成半共格界面 , 且界面存在 Al (111) / / Al 2O 3 ( 1120) 的共格关系。界面干净无任何反应物。接近界面的 Al 基体中出现了柏氏矢量为 b= 1/ 3 [ 111 ] 弗兰克不全刃位错 , 该刃位错引起界面附近基体中明显的晶格应变场 , 位错周围晶格变形场的范围约为 20～30 层原子面宽度 , 而在 Al 2O 3颗粒靠近界面的区域中未观察到位错等缺陷。并从晶体学角度对界面的形成机制进行了分析。     

Dynamic mechanical response of a 1060 Al/Al2O3 composite

The flow stress of a 1060 Al/Al₂O₃ composite increases rapidly with strain rate due to the higher dislocation accumulation rate and the increasing strength of dislocation barriers. The Al/Al₂O₃ interfaces were found to be well bonded even after high-rate deformation of the composite. MgAl₂O₄ particles observed at Al/Al₂O₃ interfaces in the composite of the present study are thought to improve the interface strength. Unlike in pure aluminium, a well-developed cell structure was not observed in the deformed 1060 Al/Al₂O₃ composite. The absence of a well-developed cell structure is thought to result from a more homogeneous slip distribution in the composite.     

Dynamic mechanical analysis of prestrained Al2O3/Al metal-matrix composite

The effect of prestraining on the elastic modulus,E, and damping capacity, tan, of 10 and 20 vol% Al₂O₃ particle-reinforced composites has been investigated as function of temperature using dynamic mechanical analysis. Both elastic modulus and damping capacity were found to increase with volume fraction. At 10 vol% the modulus and damping were relatively insensitive to prestrain. However, at 20 vol% it was observed that the modulus decreased with increasing prestrain while damping increased significantly. These results are discussed in terms of fraction of broken particles, particle size, and differential in thermal expansion between the matrix and Al₂O₃ particulate.     

Sliding wear of self-mated Al2O3-SiC whiskerreinforced composites at 23–1200°C

Microstructural changes occurring during sliding wear of self-mated Al₂O₃-SiC whiskerreinforced composites were studied using optical, scanning electron microscopy and transmission electron microscopy. Pin-on-disc specimens were slid in air at 2.7 m s^–1 sliding velocity under a 26.5 N load for 1 h. Wear tests were conducted at 23, 600, 800 and 1200°C. Mild wear with a wear factor of 2.4 x 10^–7–1.5 x 10^–6 mm³ N^–1 m^–1 was experienced at all test temperatures. The composite showed evidence of wear by fatigue mechanisms at 800°C and below. Tribochemical reaction (SiC oxidation and reaction of SiO₂ and Al₂O₃) leads to intergranular failure at 1200°C. Distinct microstructural differences existing at each test temperature are reported.Resident Research Associate at NASA Lewis Research Center.     

Al2O3 and Al2O3--TiN wear resistance in a simulated biological environment

Alumina is widely used as a biomaterial because of its high biocompatibility and its good mechanical properties except toughness. In this study, a composite material Al₂O₃–TiN is considered as an alternative, the addition of TiN improving the mechanical properties of alumina. The wear behaviour of Al₂O₃ and Al₂O₃–TiN in aqueous solutions simulating living environments has been thus compared using a pin on disc wear-testing machine. The results show that the mechanisms of material removal during wear are different. For alumina, a mechanical wear mechanism is observed, reduced by the lubricating action of the wet media, and alumina–TiN is worn by a combination of tribochemical and abrasive effects.