超声-压力场耦合作用下半固态铝铜合金中富铁相的形成机理及调控机制

Iron is considered to be a very harmful impurity in aluminum alloys, which always accumulates in recycling aluminum alloys. It is critical to control the detriment of the iron-rich intermetallics in order to maintain the high efficiency of utilization of recycled aluminum alloys. In this proposal, the formation and regulatory mechanism in the 2A16 Al-Cu-based alloys are investigated when applying high energy ultrasonic and the pressure fields during the semi-solid solidification, in order to reduce the detrimental effect of iron-rich intermetallics on aluminum alloys. The formation and regulatory mechanism of iron-rich intermetallics in semi-solid Al-Cu alloys under coupling ultrasonic and pressure fields is studied. The research focuses on the effect of physical ultrasonic and pressure fields on the type of iron-rich intermetallics, the formation sequences, the formation reactions and the mechanism of nucleation and its growth in semi-solid Al-Cu-based alloys. The coupling function mechanism of ultrasonic and pressure fields on the formation of iron-rich intermetallics are clarified based on numerical simulations and experimental validations. Furthermore, the quantitative relationship among the semi-solid processing, the iron-rich intermetallics characteristics and the mechanical properties is established. Ultimately, the regulatory mechanism of iron-rich intermetallics in semi-solid Al-Cu alloys under coupling ultrasonic and pressure fields is achieved. This proposal also introduces and promotes the high efficient utilization of resources and green casting. The expansion of solidification theory of special casting in aluminum alloys is listed. The achievement of the project is supportive for the theoretical and technological development of the high performance and low cost semi-solid aluminum alloys.

铁是铝合金中最有害的杂质元素，废铝再生时铁将不断累积，控制富铁相的危害是促进废铝回收和高效利用的关键环节。本项目以高铁含量的2A16铝铜合金为研究对象，将超声和压力场耦合作用于半固态铝熔体，研究超声-压力场耦合作用下半固态铝铜合金中富铁相的形成机理及调控机制，达到降低铝合金中富铁相危害的目的。重点研究超声和压力场耦合作用下铝铜合金半固态凝固过程中富铁相的类型、形成顺序、相变反应、形核与长大机制的演变规律。采用数值模拟和实验验证相结合，分析超声和压力场的交互作用和综合效应机制，明晰超声-压力场作用下富铁相形成的耦合作用机制。建立半固态条件-富铁相特征-力学性能的定量关系，实现超声-压力场耦合作用下富铁相的调控机制。本项目的实施不仅有利于实现资源循环高效利用和绿色铸造，还将丰富铝合金特种铸造凝固理论，同时为开发高性能、低成本的半固态铝合金材料提供理论支撑和技术指导。

杂质铁是铝合金中最有害的杂质元素，废铝再生时铁将不断累积，控制富铁相的危害是促进废铝回收和高效利用的关键环节。本项目以高铁含量2A16铝铜合金为研究对象，基于明晰超声和压力耦合场作用下富铁相的形成机理和调控机制的目标，系统的研究了中和变质元素、单一压力场、超声和压力耦合场作用下半固态铝铜合金中富铁相的形成机理及组织性能演变规律，明晰了超声和压力场耦合作用下铝铜合金半固态凝固过程中富铁相的类型、形成顺序、相变反应、形核与长大机制的演变规律。发现耦合场可以显著的促进富铁相的形核，同时降低合金的扩散系数，从而抑制富铁相的长大，显著地降低富铁相的尺寸，同时促进汉字状富铁相的形成，抑制或减少针状富铁相的形成，减少杂质Fe对合金力学性能的危害。同时采用数值模拟和实验验证的方法，分析了超声和压力场的交互作用和综合效应机制，最终明晰了超声和压力耦合场对富铁相形成的耦合作用机理，发现相比单一超声场，超声和压力耦合场会使空化效应的强度和区域增大，还可以改变熔体内部压力分布从而导致熔体内部形成更强烈的对流。同时耦合场作用下形成的大量晶核促进更多的晶核产生和晶核游离，最终形成细小均匀的凝固组织。超声-压力耦合作用可以消除单一超声作用导致的铸锭内部晶粒细化的差异性，微观组织被改善的均匀程度明显增强。同时基于组织与力学性能定量计算和富铁相断裂机理，总结了富铁相的调控机制。本项目解决了超声和压力场对富铁相形成的演变规律及耦合作用机制、超声和压力场耦合作用下富铁相调控机制等重大科学问题，丰富了铝合金特种铸造凝固理论。本项目的实施有利于实现资源循环高效利用和绿色铸造，可以满足交通、航空航天、军用等领域对低成本、高性能铝合金的重大需求。