AA7050铝合金强韧性和成形性改善的轧制工艺优化及机理研究

发布时间：2018-03-21 00:31

  本文选题：7xxx系铝合金　切入点：再结晶　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：随着交通业对节能减排和安全寿命的要求不断提高,这就对工程材料的轻量化和抗损伤容限能力提出了更高的要求。高强7系铝合金具有更高的比强度、良好的韧性和耐腐蚀性能,是实现汽车产业等轻量化的潜在备选材料。但其成形性较差,成为了制约其应用发展的瓶颈。止前对高强度7系铝合金的研究主要集中在中厚板,而缺少对其薄板成形性以及强韧性的系统研究。在此背景下,本文主要通过不同的轧制工艺来优化组织和性能,系统地研究了不同轧制温度和粒子尺寸对组织和性能的影响规律。此外,针对工业上对于复杂工件成形的要求及现有工艺复杂且成本高的现状,开发出一种能实现AA7050铝合金高应变速率超塑性成形的板材制备工艺。通过变形-组织-性能之间关系的研究,以期为高强铝合金在轻量化产业上的应用提供理论依据和技术支持。主要研究结论如下:通过对AA7050铝合金的热加工性能分析表明,在380-420 ℃和0.001-0.18 s-1范围内具有好的加工性能,而在360-420 ℃和0.1-10 s-1范围内会产生变形失稳。好的加工性能主要是因为连续动态再结晶的发生造成的,其容易在高的变形温度、大变形量、低应变速率或者高应变速率下发生。大尺寸(1μm)的粒子可以产生大粒子激发形核效应,其可以有效使得变形织构和再结晶织构弱化并可以有效使得再结晶组织细化,从而有利于改善板材的断裂韧性和成形性。变形温度的降低有利于铝合金中变形储能的增加和再结晶晶粒细化。深冷轧制可以促进剪切带的形成,增加了再结晶形核点并去除不利于成形性的Cube织构组分。另外,深冷轧制可以有效抑制动态应变时效的产生,从而获得较好的冷轧变形能力并降低了形成大粒子激发形核效应的临界粒子尺寸。高温变形过程中亚晶可以通过连续动态再结晶机制不断形成具有完全大角度晶界的细小晶粒,同时新形成的细小再结晶晶粒之间容易发生晶界滑动,两者协调作用可以实现高应变速率超塑性。
[Abstract]:With the increasing demand of transportation industry for energy saving and emission reduction and safety life, the lightweight and anti-damage tolerance of engineering materials are required. The high-strength 7-series aluminum alloy has higher specific strength. Good toughness and corrosion resistance are potential alternative materials to realize lightweight in automobile industry. However, their poor formability has become a bottleneck restricting the development of their application. The research on high-strength 7-series aluminum alloy before stopping is mainly focused on medium and thick plates. However, there is no systematic research on the formability and strength and toughness of the sheet metal. Under this background, the microstructure and properties are optimized by different rolling processes. The effects of rolling temperature and particle size on microstructure and properties are systematically studied. In this paper, we have developed a kind of plate preparation technology which can realize high strain rate superplastic forming of AA7050 aluminum alloy. The relationship between deformation, microstructure and properties has been studied. In order to provide theoretical basis and technical support for the application of high-strength aluminum alloy in lightweight industry, the main conclusions are as follows: through the analysis of the hot working properties of AA7050 aluminum alloy, it is shown that the high strength aluminum alloy has good processability in the range of 380-420 鈩，

本文编号：1641470