Next generation of free machining aluminium alloys

易切削合金（FMA）使用低熔点添加元素如Pb、Bi和Sn来提供断屑机制，这赋予铝合金优异的易切削性能。然而，环境立法正在推动铅的去除，同时减少铋和锡等重元素的添加。这需要开发一系列新的无铅FMA，其具有与含Pb合金相同的可加工性，但具有较低水平的Bi和/或一部分基于Fe和Si的硬第二相颗粒以用作断屑剂。此外，基于熔体调节技术的替代液体金属处理的应用提供了对断屑机制产生显著影响的能力。

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.