铸造耐热铝合金的研究进展及展望

Progress and Prospect of Cast Heat-resistant Aluminum Alloy

随着资源和环境问题日益突出,世界各国均对汽车工业节能减排提出了迫切的要求。用铸造耐热铝合金替代铸铁可大幅度减轻车身质量因此铸造耐热铝合金成为新一代汽车发动机缸体和活塞的主流材料。然而,商业铸造铝合金的高温性能并不能较好地满足当前应用需求,并且快速凝固铝合金和铝基复合材料受限于高昂成本和制备复杂性而不能被大范围推广。因此,目前学术界和产业界的研究多集中于铸造铝合金耐热性能的提升和新型高温强化机理的探索。铸造耐热铝合金可分为三个体系:Al-Si、Al-Cu和Al-Mg。其中,Al-Si合金因具备优异的铸造流动性等成型特性而被大范围研究和应用。通过添加多种元素进行合金化,在铝合金中形成各种熔点高、热稳定性好的金属间化合物阻碍晶界运动和位错滑移是目前主流的强化方式。而经过热处理和Si相变质,进一步调控合金的组织结构也是一种重要的强化手段。此外,优化熔炼和铸造工艺,减少夹杂和铸造缺陷对提高铸造铝合金的高温强度也有重要意义。值得注意的是,近年来的研究表明第二相的三维网状互联结构与合金高温性能的提升存在密切关系。在高温强度以外,国内外学者也致力于研究铸造铝合金的蠕变性能、疲劳性能和热暴露性能。本文从体系组成和国内外商用产品两方面归纳了铸造耐热铝合金的发展和应用,分析了铸造铝合金组织结构调控的基本手段,总结了铸造铝合金高温性能的最新研究成果,同时对铸造耐热铝合金的未来研究方向进行了展望。

As issues of the resource and environment become increasingly prominent,countries all over the world have put forward urgent requirements for the automobile industry to reduce energy consumption and pollution emissions.At the same time,cast heat-resistant aluminum alloy has become the mainstream material for new automobile engine cylinder blocks and pistons,which replaces traditional cast iron owing to its light weight.However,the high-temperature performance of commercial cast aluminum alloys cannot well meet the current application requirements.Meanwhile,rapidly solidified aluminum alloys and aluminum composite materials cannot be widely promoted because of the high cost and the complexity of preparation.Therefore,the current academic and industrial studies mostly focus on the improvement of the heat resistance of cast aluminum alloy and the exploration of new high-temperature strengthening mechanisms.At present,cast heat-resistant aluminum alloys can be divided into three systems:Al-Si,Al-Cu,and Al-Mg.Among them,Al-Si alloys have been widely studied and applied due to their excellent casting fluidity and other molding properties.By adding a variety of elements for alloying,forming various intermetallic compounds with high melting point and good thermal stability in the aluminum alloy to hinder grain boundary movement and dislocation slip is the current mainstream strengthening method.After heat treatment and Si phase modification,further control of the alloy structure is an important strengthening method as well.In addition,optimizing smelting and casting processes,reducing inclusions and casting defects are also of great significance for improving the high-temperature strength of cast aluminum alloys.It is worth noting that recent studies have found that the three-dimensional network interconnection structure of the second phase is closely related to the improvement of the high-temperature performance of the aluminum alloy.Besides high-temperature strength,domestic and foreign scholars are still committed to the study of the creep properties,fatigue properties,and thermal exposure properties of cast aluminum alloys.In this paper,the development and application of cast heat-resistant aluminum alloys are summarized from both the system composition and domestic and foreign commercial products,and the basic methods of organizational and structural control of cast aluminum alloys are analyzed.Moreover,the latest study results on the high-temperature properties of cast aluminum alloys are generalized.Finally,the future directions to the cast heat-resistant aluminum alloys are proposed.