时效处理对7075铝合金摩擦学性能的影响

Effect of aging on tribological performances of 7075 aluminium alloy

研究了经超长时效处理后7075铝合金的力学性能、显微组织及摩擦学性能。结果表明:7075铝合金的硬度及强度具有双峰时效的特征,两个峰时效样品的硬度和拉伸强度相差不大,但伸长率有一定区别。与未经热处理的样品相比,时效处理后样品尽管摩擦系数较大,但摩擦系数随载荷的变化较小。随载荷增加,不同模式处理的铝合金均出现了从轻微磨损向严重磨损的转变,但经时效处理后样品磨损率明显小于未经热处理的样品,且第二峰样品的磨损率较小。时效处理后样品出现由轻微磨损向严重磨损转变的临界载荷显著提高,且第二峰样品临界载荷明显高于第一峰样品,表现出更优异的摩擦学性能;这可能归结于第二峰时效时合金组织中析出了数量更多、分布更均匀、颗粒更细小的强化相η'(MgZn2)的缘故。不同模式处理的铝合金磨损机制相近:在轻微磨损时以磨粒磨损和氧化磨损为主,严重磨损时以粘着磨损和剥层磨损为主。

Microstructure, mechanical properties and tribological properties of 7075 aluminum alloy after super-length aging treatment were investigated. The results show that the hardness and strength of 7075 aluminum alloy exhibit double peaks aging features. Although the hardness and tensile strength of the samples under two peak-aging are almost same, the elongation shows certain difference. The friction coefficients of two peak-aged samples are higher than that of as-received sample （ non heat-treatment） , and shows few change as the load increases, and the friction coefficients of non heat-treated sample display evidently decrease as the load increases. 7075 aluminum alloy displays the transition from mild wear to severe wear, and the wear rates of aging treated sample are obviously lower than those of non heat- treated samples, and the second peak-aged sample shows the lowest wear rate among the experimental samples, as the load increases. The critical load of peak-aged sample for the transition from mild wear to severe wear are distinctly improved comparing with the as-received sample, and the critical load of second peak-aged sample is also higher than that of first peak-aged sample. The phenomenon indicats that the second peak-aged sample possesses the more excellent tribological performance, which might be attributed to the precipitate of uniform and fine secondary phase η（ MgZn2 ）. 7075 aluminum alloy with different heat treatment modes displays the similar wear mechanism： abrasive and oxidation wear are the main wear mechanisms during the mild wear period, adhesion wear and delamination wear are dominate wear mechanisms during the severe wear period.