钇在亚共晶铝硅合金中的作用研究进展

Research Progress on the Role of Yttrium in Hypoeutectic Al-Si Alloys

亚共晶Al-Si合金具有优异的铸造工艺性能和良好的力学性能,应用广泛,尤其适合大型薄壁复杂结构铸件的生产,比如燃油壳体、发动机缸套等。现代工业的进一步发展对亚共晶Al-Si合金的综合力学性能提出了更高的要求,提高亚共晶Al-Si合金的综合力学性能迫在眉睫。改善合金的组织是提高合金综合力学性能常用的一种方法。亚共晶Al-Si合金的组织包括初生α-Al、共晶相(包括共晶Al和共晶Si)、杂质相(如富Fe相)等,其中共晶Si呈粗大板片状,在合金部件服役过程中易导致应力集中而使部件失效。通过变质处理,将共晶Si形貌变质为应力集中小的麦穗状、纤维状等,能显著提高Al-Si合金的综合力学性能。因此,很多学者一直在从事变质共晶Si的研究。化学变质共晶Si操作简单、价格低廉,即在合金熔炼过程中加入一种或几种化学物质,改变共晶Si形核和生长的方式,从而改变其形貌。近年来,很多学者一直在寻找更合适的亚共晶Al-Si合金共晶Si变质剂,并取得了丰硕的成果。Na和Sr是应用比较早且十分广泛的变质剂,Sb也是一种常见的变质剂,但它们在工业化使用过程中都有较大的缺点,如Na易挥发、污染环境等,Sr易使合金熔体吸气而导致气孔和氧化夹杂,Sb大量使用对人体有害。大量研究表明,Y是一种有效的共晶Si变质剂,但除了对共晶Si的变质作用,Y对亚共晶Al-Si合金中的其他组织也有影响,如初生α-Al、富Fe杂质相等。为了更加有效地利用Y并促进Y在亚共晶Al-Si合金中的工业化使用,本文对Y及Y与其他因素耦合在亚共晶Al-Si合金中的作用进行了综述,包括其对共晶Si的变质作用、对初生α-Al的影响及共晶Si的变质机理等,同时对后续研究中需要注意的问题进行了阐述并对未来发展方向进行了展望。

Due to excellent casting properties and good mechanical properties,hypoeutectic Al-Si alloy is widely used,especially suitable for the production of large thin-walled complex structure castings,such as fuel shell,engine cylinder liner,etc.The further development of modern industry puts forward higher requirements for the comprehensive mechanical properties of hypoeutectic Al-Si alloys,and it is urgent to improve the comprehensive mechanical properties of hypoeutectic Al-Si alloys.Improving microstructure is a common method to improve the alloy's comprehensive mechanical properties.The microstructure of hypoeutectic Al-Si alloy includes primaryα-Al,eutectic phase(including eutectic Al and eutectic Si),impurity phases(such as Fe rich phase),etc.The eutectic Si is a thick plate,which is easy to lead to stress concentration and failure during the service process of alloy parts.Though modification,the morphology of eutectic Si was changed into wheat ear and fiber with small stress concentration,can significantly improve comprehensive mechanical properties.Therefore,many scholars have been engaged in the study of modified eutectic Si.Chemical modification of eutectic Si is simple and cheap.One or several chemical substances are added during the alloy melting process to change the nucleation and growth mode of eutectic Si and change its morphology.In recent years,many scholars have been looking for a more suitable eutectic Si modifier for hypoeutectic Al-Si alloys,and have achieved fruitful results.Na and Sr are used earlier and widely,and Sb is also a common modifier.However,they have great shortcomings in industrial use,such as Na volatilizes easily and pollutes the environment,Sr easily makes the alloy melt aspirate,resulting in porosity and oxide inclusion in the aluminum matrix,and Sb is harmful to the human body with heavy use.Many researches results show that Y is an effective eutectic Si modifier.While in addition to modified eutectic Si,Y also affects other microstructures of hypoeutectic Al-Si alloy,such as primaryα-Al and Fe rich impurities.To make more effective use of Y and promote the industrial application of Y in hypoeutectic Al-Si alloys,the role of Y and Y coupled with other factors in hypoeutectic Al-Si alloys were reviewed,including the eutectic Si modification,the effects on primaryα-Al and the mechanism of eutectic Si modification.Meanwhile,the problems needing attention in the follow-up researches were described,and the future development direction was proposed.