原位生成MoB增强Cu-Sn-Al合金复合材料的摩擦学性能研究

采用快速热压烧结方法成功制备了原位生成MoB增强的Cu-Sn-Al合金复合材料，研究了增强体添加含量对复合材料体系摩擦学性能的影响，并对其摩擦磨损机制进行了分析. 研究表明:在Cu-5Sn合金基体中添加MoAlB陶瓷颗粒后，烧结过程中，层状结构MoAlB陶瓷中的Al元素能够扩散到基体中，生成原位MoB增强Cu-Sn-Al合金复合材料. 此外，复合材料体系的硬度随着MoAlB添加量的增加逐渐提高，与Cu-5Sn合金相比，当添加MoAlB质量分数为30%时，复合材料硬度值提高了约5倍. 同时，随着添加MoAlB陶瓷颗粒含量的增加，复合材料体系摩擦系数和磨损率逐渐降低，当添加的MoAlB陶瓷颗粒质量分数为30%时，复合材料摩擦系数和磨损率分别低至0.33和5.4×10?5 mm3/(N·m). 由于原位生成MoB颗粒的钉扎效应，在摩擦过程中能够抑制基体材料的塑性变形，使得材料体系的硬度显著提高，磨损率明显降低，摩擦过程中表面生成的摩擦氧化物，能够降低材料体系的黏着磨损和二体磨粒磨损，可以起到优异的抗磨减摩效应. 

Tribological Properties of In-Situ MoB Reinforced Cu-Sn-Al Composites

In this study, in-situ generating MoB ceramic reinforced Cu-Sn-Al alloy composites were successfully prepared by sintering the raw materials of Cu, Sn and MoAlB powders via fast hot-press sintering route. The influence of the content of MoAlB ceramic reinforcement on the microstructure and tribological properties of the as-prepared composites were studied, and the friction and wear mechanisms of the composites were discussed as well. It was established that when the MoAlB ceramic particles were doped in the Cu-5Sn alloy matrix, Al element in the layered MoAlB ceramic could be diffused out of MoAlB matrix and diffused into the Cu-5Sn alloy matrix during the sintering process, resulting in the formation of in-situ MoB ceramic particles reinforced Cu-Sn-Al alloy matrix composites. Because of the dispersion strengthening effect of in-situ forming MoB particles, the as-prepared Cu matrix composites could exhibit enhanced mechanical properties. It was confirmed that the Vickers hardness, compressive strength and flexural strength of as-prepared composites were greatly improved in comparison with as-prepared Cu-5Sn alloy. When the mass fraction of MoAlB was as high as 30%, the hardness value of the composite was about 321.2 HV_0.1, which was approximately five times higher than that of as-prepared Cu-5Sn alloy. As the mass fraction of MoAlB was as high as 10%, the as-prepared Cu matrix composite had the highest compressive strength and flexural strength, where the compressive strength and flexural strength were 1 156.5 MPa and 822 MPa, respectively. When the mass fraction of MoAlB further increased, the compressive strength and flexural strength of as-prepared gradually decreased. Furthermore, the friction coefficient and wear rate of as prepared composites gradually came down with the mass fraction of MoAlB increasing up to 30%. For as-prepared Cu-5Sn alloy, the friction coefficient and wear rate were 0.67 and 3.60×10?4 mm3/(N·m), respectively. The main wear mechanisms were two-body abrasive and adhesive wear. When the mass fraction of MoAlB ceramic increased from 10% to 20%, the friction coefficient and wear rate of as-prepared Cu matrix composites came down from 0.48 and 1.75×10?4 mm3/(N·m) to 0.46 and 1.30×10?4 mm3/(N·m), respectively. Due to the pining effect of in-situ generated MoB particles, the plastic deformation of the matrix material in the friction process can be inhibited, which could obviously reduce the two-body abrasive and adhesive wear. Besides, the addition of MoAlB also could promote the tribo-oxidation reaction during the sliding process, in which the tribo-oxidation products mainly consisted of the oxides of Mo and B. The tribo-oxidation products generated on the worn surface during the sliding can reduce the adhesive wear and two-body abrasive wear, which can provide excellent lubricating effect to reduce friction and wear during the sliding process. Hence, as the mass fraction of MoAlB ceramic climbed up to 30%, the as-prepared Cu matrix composite exhibited better lubricating effect, where the friction coefficient and wear rate were as low as 0.33 and 5.4 × 10?5 mm3/(N·m), respectively.