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一段时间以来,铝-铅(Al-Pb)系合金一直被认为是发动机曲轴轴瓦的理想材料,现在可以采用连铸和粉末冶金工艺来生产钢背轴瓦。Al-Pb系合金需要特殊的冶金工艺,合金凝固期间在初次固相出现的温度下,仅有1.5%的Pb熔于Al。其余的Pb以熔滴形式析出,熔滴周围的合金仍为熔化状态,由于密度差异使这些熔滴偏析,应用普通的铸造方法不能获得Pb在整个铝基体上的均匀分布。
Aluminum-lead alloys have long been considered as ideal materials for engine crankshaft bearings, and continuous casting and powder metallurgy processes are now available to produce steel backing bearings. Al-Pb-based alloys require a special metallurgical process where only 1.5% of the Pb melts in Al during the initial solid-phase temperature of the alloy during solidification. The rest of the Pb precipitates as droplets and the alloy around the droplets is still molten. Due to the difference in density, these droplets are segregated and the uniform casting of Pb can not be obtained uniformly over the entire aluminum substrate by conventional casting methods.