Al-TiO_2-B_2O_3反应体系中B_2O_3/TiO_2摩尔比对热扩散反应合成铝基复合材料磨损性能的影响

Effect of B_2O_3/TiO_2 Mole Ratios in Al-TiO_2-B_2O_3 Reaction System on the Wear Resistance of in-situ Exothermic-Dispersion Reaction Synthetic Al-Based Composites

利用Al-TiO2-B2O3体系热扩散反应合成(XD)法制备了铝基复合材料;采用销-盘摩擦磨损试验机考察了所制备的铝基复合材料在干摩擦条件下同GCr15钢配副时的磨损性能;采用扫描电子显微镜和光学金相显微镜观察分析了复合材料微观组织结构及其磨损表面和剖面形貌,探讨了其磨损机理.结果表明:所制备的铝基复合材料的磨损性能随Al-TiO2-B2O3反应体系中B2O3/TiO2摩尔比的增加而提高;复合材料的磨损质量损失随着滑动速度的增加而增加,当滑动速度为0.9m/s左右时最大,随后开始减小;磨损质量损失与滑动距离基本呈线性关系.当B2O3/TiO2摩尔比为0.0时,增强相由Al2O3和Al3Ti组成,相应的复合材料的抗磨性能较差,其磨损主要表现为Al3Ti的犁沟切削、亚表层剥落、塑性基体流失导致Al2O3颗粒裸露脱落以及Al3Ti棒断裂导致的磨粒磨损;加入B2O3后,棒状Al3Ti的数量减少,有利于基体晶粒细化,提高复合材料强度和塑性,故抗磨性能提高.当B2O3/TiO2摩尔比为1.0时,复合材料中的Al3Ti基本消失,抗磨性能显著改善,主要磨损机制为粘着磨损和轻微磨粒磨损.

A series of Al-based composites were fabricated from the Al-TiO2-B2O3 reaction systems of different B2O3/TiO2 mole ratios, using exothermic dispersion in-situ synthesis. A pin-on-disc test rig was performed to evaluate the wear resistance of the resulting Al-based composites sliding against AISI52100 steel unlubricated condition at ambient temperature. An optical microscope and a scanning electron microscope were used to observe the microstructure of the Al-based composites and the morphologies of the worn surfaces and worn cross-sections. The results indicated that the wear mass loss of the Al-based composites increased almost linearly with increasing sliding distance. It increased with increasing sliding velocity until coming to the maximum at a velocity of 0.9 m/s, then it slightly decreased with further increase of the sliding velocity. The incorporation of B2O3 in the reaction system helped to improve the wear resistance of the Al-based composites, thus the wear resistance of the composites increased with increasing B2O3/TiO2 mole ratio in the reaction system. The reinforcements were composed of Al2O3 particulates and rod-like Al3Ti in the absence of B2O3 in the reaction system, in this case the corresponding composite had poor wear resistance, because of the severe ploughing action of the wear debris detached from the Al3Ti rods. With increasing B2O3/TiO2 mole ratios in the reaction system, the amount of Al3Ti rods decreased, which was beneficial to decrease the grain size of the matrix grains finer, therefore the strength and plasticity of the composites were greatly increased. Moreover, the Al-based composites made from the Al-TiO2-B2O3 reaction systems of different B2O3/TiO2 mole ratios had differences in terms of the wear mechanisms as well. Namely, the Al-based composite made in the absence of B2O3 was dominated by abrasive wear and slight adhesion wear, while that made at a B2O3/TiO2 mole ratio of 1.0 was dominated by adhesion wear and slight abrasive wear.