Guoqin Chen

Property characteristics of a AlNp/Al composite fabricated by squeeze casting technology

TiB_(2p )/Al 合成成功地被制作由压榨扔技术。它的机械并且 tribological 性质被评估。Ti-Alintermetallic 化合物的消除被衍射(XRD ) 学习的 X 光检查证实。在 45% 体积部分，在周围的温度的弯曲强度是 934 MPa。并且破裂模式包括了艾尔矩阵的可锻的失败和 TiB_2 粒子的易碎的骨折。在干燥滑动穿模式，严重塑料变丑和粘合剂穿在 SiC_p/Alcomposite 的穿的表面上被发现。但是粘附或磨耗(量) 的明显的特征都没在 theTiB_(2p ) 的上被观察 /Al composites。在稳定的阶段， SiC_p/Al 的磨擦系数合成是大约 0.6。当时 TiB_(2p )/Al 的合成仅仅关于 0.16-0.17。

The thermal expansion and mechanical properties of high reinforcement content SiCp/Al composites fabricated by squeeze casting technology

Abstract With mixing different sized SiC particles, high reinforcement content SiCp/Al composites ( V p =50, 60 and 70%) for electronic packaging applications were fabricated by squeeze casting technology. The composites were free of porosity and SiC particles distributed uniformly in the composite. The mean linear coefficients of thermal expansion (20–100 °C) of SiCp/Al composites ranged from 8.3 to 10.8×10 −6 /°C and decreased with an increase in volume fraction of SiC content. The experimental coefficients of thermal expansion agreed well with predicted values based on Kerners model. The Brinell hardness increased from 188.6 to 258.0, and the modulus increased from 148 to 204 GPa for the corresponding composites. The bending strengths were larger than 370 MPa, but no obvious trend between bending strength and SiC content was observed.

Mechanical properties of Cf/Mg composites fabricated by pressure infiltration method

The carbon fibers and the woven reinforced magnesium matrix composites were fabricated by pressure infiltration method. Effects of fiber species, fiber arrangement, hybrid particles and environment temperature on microstructures and properties of the composite were studied. Results showed that the mechanical properties at ambient temperature were affected by interfacial reaction. The magnesium matrix composites reinforced with graphite fibers showed higher strength and elastic modulus due to less interfacial reaction. During loading, the fibers were pulled out and the load was transferred through the interfaces, then the fiber bundles were fractured, finally the whole specimen failed. The introduction of hybrid SiC particles during fabrication can improve the mechanical properties of the magnesium matrix composites. Moreover, taking orthogonal carbon fiber woven as reinforcement can modify the anisotropy and reliability of materials.

Effect of volume fraction on microstructure and mechanical properties of Si3N4/Al composites

Abstract Si3N4 particles reinforced aluminium matrix composites (Si3N4/Al) with different particle volume fractions (45%, 50%, and 55%) were fabricated by pressure infiltration method. The effects of Si3N4 volume fraction and T6 treatment on microstructure and mechanical properties of Si3N4/Al composite were investigated. The results show that Si3N4/Al composites are well infiltrated with good particles dispersion and no apparent porosity or significant casting defects are observed. High density of dislocations in Al matrix around Si3N4 particles is observed. The bending strength of Si3N4/Al composites decreases with an increase in Si3N4 volume fraction, and can be greatly improved by T6 treatment. Elastic modulus of composites increases linearly with Si3N4 volume fraction. At a lower Si3N4 volume fraction, more tearing ridge and dimples with elongation are observed. T6 heat treatment shows minor effect on the fracture surface of composite.

Thermal expansion and mechanical properties of high reinforcement content SiCp/Cu composites fabricated by squeeze casting technology

High reinforcement content SiC(subscript p)/Cu composites (φ(subscript p)=50%, 55% and 60%) for electronic packaging applications were fabricated by patent cost-effective squeeze-casting technology. The composites appear to be free of pores, and the SiC particles are distribute uniformly in the composites. The mean linear coefficients of thermal expansion (CTEs, 20-100 ℃) of as-cast SiC(subscript p)/Cu composites range from 8.8×10^(-6)℃^(-1) to 9.9×10^(-6) ℃^(-1) and decrease with the increase of SiC content. The experimental CTEs of as-cast SiC(subscript p)/Cu composites agree well with the predicted values based on Kerner model. The CTEs of composites reduce after annealing treatment due to the fact that the internal stress of the composite is released. The Brinell hardness increases from 272.3 to 313.2, and the modulus increases from 186 GPa to 210 GPa for the corresponding composites. The bending strength is larger than 374 MPa, but no obvious trend between bending strength and SiC(subscript p) content is observed.

Microstructure and performance of Al-Si alloy with high Si content by high temperature diffusion treatment

Abstract The Al-Si alloy with high Si content was prepared by pressure infiltration. Microstructure observation shows that three-dimensional structure (3D-structure) is obtained from irregular sharp Si particles via high temperature diffusion treatment (HTDT). Flat Si-Al interfaces transform to smooth curves, and Si phases precipitate in Al and Si-Al interface. The bonding of Si-Al interface is improved by HTDT, which improves the mechanical performance of Al-Si alloy. The bending strength of 3D-Al-Si alloy increases by 6% compared with that of Al-Si alloy, but the elastic modulus changes a little. The coefficient of thermal expansion (CTE) of the 3D-Al-Si alloy is 7.7×10−6/°C from 20 °C to 100 °C, which decreases by 7% compared with that of Al-Si alloy. However, HTDT has little effect on the thermal conductivity of Al-Si alloy.

Effects of extrusion deformation on mechanical properties of sub-micron Si3N4p/2024 composite

Abstract Si 3 N 4p /2024Al composite was fabricated by squeeze casting method and treated by extrusion deformation. Microstructure analyses indicate that Si 3 N 4 particles in the composite are in cylindrical polyhedron shape. Extrusion deformation is beneficial to uniform distribution of Si 3 N 4 particles and improves the relative density of Si 3 N 4p /2024Al composite. Tensile strength of Si 3 N 4p /2024Al composite increases by 76.6% after T6 treatment, and after extrusion and T6 treatment it is by 57.6% more than T6 treatment only. Elastic modulus of Si 3 N 4p /2024Al composite increases a little after T6 treatment but increases by 33.5% after extrusion deformation.

Effects of Gd element and SiC particles on microstructures of Cf/Mg composites.

In present work, Cf/Mg-8Gd and SiC+Cf/Mg-8Gd composites were fabricated by squeeze infiltration method. Gd2O3 coating layers were found on the surface of the carbon fibers in these two kinds of the composites, while GdC2 precipitations were found in the hybrid reinforced composite only. Owing to this phenomenon, the coating layer in SiC+Cf/Mg-8Gd composite (88 nm) was much thinner than the one without the SiC particles (160 nm). The Gd2O3 coating layer formed on the surface of carbon fibers can improve the wettability between carbon fibers and magnesium alloy.

Effect of TiN coating on microstructure of Tif/Al composite

In the present work, Ti fibre reinforced Al matrix composites (Ti(f)/Al) were fabricated by pressure infiltration method. In order to suppress the severe Ti-Al reaction and reduce the formation of brittle TiAl(3) phase, a TiN layer was coated on Ti fibres by an arc ion plating method before composite preparation. A thin TiN layer was coated on the Ti fibre surface, and the maximum and minimum thickness values of layer were about 3.5 and 1μm, respectively. Prefer orientation of TiN on (111) and (200) was found by XRD analysis. A thin and uniform TiAl(3) layer was observed in Ti(f)/Al composite. However, after coated with TiN layer, no significant reaction layer was found in (Ti(f)+TiN)/Al composite. Segregation of Mg element was found in Ti(f)/Al composite, and the presence of TiN layer showed little effect on this behaviour. Due to the large CTE difference between Ti fibre and Al matrix, high density dislocations were observed in the Al matrix. Meanwhile, fine dispersed Mg(2)Al(3) phases were also found in Al matrix. Ti fibre is mainly composed of α- and β-Ti. Small discontinuous needle-like TiAl(3) phases were detected at TiN/Al interface, which implies that the presence of TiN layer between the Ti fibre and Al matrix could effectively hinder the formation of TiAl(3) phases.

Effect of thermal-cooling cycle treatment on thermal expansion behavior of particulate reinforced aluminum matrix composites

Abstract Two micron SiC particles with angular and spherical shape and the sub-micron Al2O3 particles with spherical shape were introduced to reinforce 6061 aluminium by squeeze casting technology. Microstructures and effect of thermal-cooling cycle treatment (TCCT) on the thermal expansion behaviors of three composites were investigated. The results show that the composites are free of porosity and SiC/Al2O3 particles are distributed uniformly. Inflections at about 300 °C are observed in coefficient of thermal expansion (CTE) versus temperature curves of two SiCp/Al composites, and this characteristic is not affected by TCCT. The TCCT has significant effect on thermal expansion behavior of SiCp/Al composites and CTE of them after 3 cycles is lower than that of 1 or 5 cycles. However, no inflection is observed in Al2O3p/Al composite, while TCCT has effect on CTE of Al2O3p/Al composite. These results should be due to different relaxation behavior of internal stress in three composites.