Next generation of free machining aluminium alloys

自由加工合金（FMA）使用低熔点添加的元素，如Pb， Bi和Sn来提供断片机制，从而赋予铝合金优异的自由加工性能。然而，环境立法推动了铅的去除，同时减少了Bi和Sn等重元素的添加。这需要开发一种新的无铅FMA，具有与含铅合金相同的可加工性，但具有较低水平的Bi和/或基于Fe和Si的硬第二相颗粒的一小部分作为切屑断路器。此外，基于熔体调节技术的替代液态金属处理的应用提供了对切屑断裂机制产生巨大影响的能力。

Free Machining alloys (FMA) use low melting point additions of elements such as Pb, Bi and Sn to provide chip breaking mechanisms, which impart excellent free machining properties to aluminium alloys. Environmental legislation is, however, driving the removal of Pb, together with a reduction in heavy-element additions such as Bi and Sn. This requires the development of a new range of Pb-free FMA with equivalent machinability to that of the Pb-containing alloys but with lower levels of Bi and/or a fraction of hard second phase particles based on Fe and Si to act as chip breakers. Moreover, the application of alternative liquid metal treatments based on melt conditioning techniques offers the ability to have a dramatic impact on the chip breaking mechanisms.