本文選題：7xxx系鋁合金　切入點：再結(jié)晶　出處：《北京科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：隨著交通業(yè)對節(jié)能減排和安全壽命的要求不斷提高,這就對工程材料的輕量化和抗損傷容限能力提出了更高的要求。高強7系鋁合金具有更高的比強度、良好的韌性和耐腐蝕性能,是實現(xiàn)汽車產(chǎn)業(yè)等輕量化的潛在備選材料。但其成形性較差,成為了制約其應(yīng)用發(fā)展的瓶頸。止前對高強度7系鋁合金的研究主要集中在中厚板,而缺少對其薄板成形性以及強韌性的系統(tǒng)研究。在此背景下,本文主要通過不同的軋制工藝來優(yōu)化組織和性能,系統(tǒng)地研究了不同軋制溫度和粒子尺寸對組織和性能的影響規(guī)律。此外,針對工業(yè)上對于復(fù)雜工件成形的要求及現(xiàn)有工藝復(fù)雜且成本高的現(xiàn)狀,開發(fā)出一種能實現(xiàn)AA7050鋁合金高應(yīng)變速率超塑性成形的板材制備工藝。通過變形-組織-性能之間關(guān)系的研究,以期為高強鋁合金在輕量化產(chǎn)業(yè)上的應(yīng)用提供理論依據(jù)和技術(shù)支持。主要研究結(jié)論如下:通過對AA7050鋁合金的熱加工性能分析表明,在380-420 ℃和0.001-0.18 s-1范圍內(nèi)具有好的加工性能,而在360-420 ℃和0.1-10 s-1范圍內(nèi)會產(chǎn)生變形失穩(wěn)。好的加工性能主要是因為連續(xù)動態(tài)再結(jié)晶的發(fā)生造成的,其容易在高的變形溫度、大變形量、低應(yīng)變速率或者高應(yīng)變速率下發(fā)生。大尺寸(1μm)的粒子可以產(chǎn)生大粒子激發(fā)形核效應(yīng),其可以有效使得變形織構(gòu)和再結(jié)晶織構(gòu)弱化并可以有效使得再結(jié)晶組織細化,從而有利于改善板材的斷裂韌性和成形性。變形溫度的降低有利于鋁合金中變形儲能的增加和再結(jié)晶晶粒細化。深冷軋制可以促進剪切帶的形成,增加了再結(jié)晶形核點并去除不利于成形性的Cube織構(gòu)組分。另外,深冷軋制可以有效抑制動態(tài)應(yīng)變時效的產(chǎn)生,從而獲得較好的冷軋變形能力并降低了形成大粒子激發(fā)形核效應(yīng)的臨界粒子尺寸。高溫變形過程中亞晶可以通過連續(xù)動態(tài)再結(jié)晶機制不斷形成具有完全大角度晶界的細小晶粒,同時新形成的細小再結(jié)晶晶粒之間容易發(fā)生晶界滑動,兩者協(xié)調(diào)作用可以實現(xiàn)高應(yīng)變速率超塑性。
[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，

本文編號：1641470