新型衬板轧制Mg-9Al-1Zn镁合金的组织控制
发布时间：2018-07-27 17:42
【摘要】：基于节能减排的迫切需求,镁合金作为轻质结构材料在航空、汽车、电子器件等领域受到了海内外学者的广泛关注。鉴于镁合金本身极限抗拉强度较低,上个世纪以来,大量研究聚焦在大变形超细晶镁合金上,大变形超细晶镁合金强度较传统粗晶材料有大幅度提高,但其室温延伸率一般较低。目前,金属领域科研工作者陆续制备了高强塑性混晶结构金属材料,然而针对混晶结构镁合金强塑性同时提高方面的研究甚少。本人所在课题组在前期研究中开发了大压下量衬板轧制(HPR)技术,该技术不仅制样简单、轧制道次少、效率高,能够大大降低镁合金板材轧制成本,具有良好的工业应用潜力;而且利用该技术获得了室温力学性能优异的、具有混晶结构的AZ91镁合金,但对混晶比例的调控尚未完全掌握、对混晶的形成机制尚未清晰。因此,本文以Mg-9Al-1Zn(AZ91)镁合金为研究对象,采用HPR技术,通过改变衬板轧制参数(温度、压下量、轧制道次)、再结晶退火参数(温度、时间),获得具有不同结构特性(尺寸、比例、织构)的混晶镁合金或细晶镁合金;为强塑性同时提升的混晶镁合金、力学性能媲美传统轧制但更节约环保的细晶镁合金的可控制备奠定基础,并对混晶的形成机制进行初步了解。另外,对单道次衬板轧制工艺制备的混晶AZ91镁合金的高温拉伸变形行为进行了研究。得出主要结论如下:(1)研究了轧制温度、压下量轧制参数对双衬板单道次轧制AZ91镁合金组织、力学性能的影响规律。优化出双衬板单道次350℃/55%压下量的轧制参数,该轧制工艺可制备具有混晶结构且力学性能(σ0.2-152MPa,σb-374MPa,δp-19.6%)较佳的AZ91镁合金薄板。(2)探索了350℃/75%压下量单道次轧制工艺制备的混晶AZ91镁合金在175℃、200℃、300℃及350℃的高温拉伸变形行为;发现混晶AZ91试样可以在200℃以上温度、1×10-3s-1应变速率拉伸条件下,表现出超塑性,且该混晶板材在300℃下拉伸时的断裂延伸率高达505%。分析认为在300℃、1.0×10-3s-1应变速率下拉伸变形的超塑性主要为动态再结晶及第二相辅助晶界滑移共同作用的结果。(3)优化了再结晶退火工艺(温度、时间)对两道次双衬板同温轧制和降温轧制AZ91镁合金组织、力学性能的影响。发现经过降温轧制及再结晶退火后,可以获得晶粒尺寸较为细小均匀(~3.2μm)的镁板。(4)实现了用波浪衬板轧制(WDR)技术制备边缘无明显开裂的AT63镁合金板材,发现WDR技术可以有效弱化镁合金轧板基面织构,揭示了弱化轧板基面织构可以提高板材加工硬化能力的作用机制,由于织构弱化导致波浪衬板轧制试样具有更高的断裂延伸率(22.5%)。
[Abstract]:Due to the urgent need of energy saving and emission reduction magnesium alloys as lightweight structural materials have been widely concerned by scholars at home and abroad in the fields of aviation automotive electronic devices and so on. In view of the low ultimate tensile strength of magnesium alloys, since last century, a large number of studies have focused on large deformation superfine grained magnesium alloys, and the strength of large deformation ultrafine grained magnesium alloys has been greatly improved compared with traditional coarse grained materials. But the elongation at room temperature is generally low. At present, researchers in metal field have prepared high strength plastic mixed crystal structure metal materials one after another. However, there is little research on the enhancement of high strength plasticity of mixed crystal magnesium alloy. In the previous research, my research group developed the (HPR) technology of large volume liner rolling. This technology is not only simple in sample preparation, less pass rolling, high efficiency, can greatly reduce the rolling cost of magnesium alloy sheet, and has a good potential for industrial application. Moreover, AZ91 magnesium alloys with excellent mechanical properties at room temperature and mixed crystal structure have been obtained by using this technique, but the control of the proportion of mixed crystals has not been fully grasped, and the formation mechanism of mixed crystals has not been clearly understood. Therefore, taking Mg-9Al-1Zn (AZ91) magnesium alloy as the research object, using HPR technology, by changing the rolling parameters (temperature, reduction, rolling pass) and recrystallization annealing parameters (temperature, time) of lining plate, different structural characteristics (size, proportion) are obtained. Texture) or fine-grained magnesium alloy, and lay a foundation for the controllable preparation of high-plasticity, simultaneous lifting, fine-grained magnesium alloy with mechanical properties comparable to that of conventional rolling but more economical and environmentally friendly. The formation mechanism of mixed crystals was also preliminarily understood. In addition, the high temperature tensile deformation behavior of mixed AZ91 magnesium alloy prepared by single pass liner rolling process was studied. The main conclusions are as follows: (1) the effects of rolling temperature and rolling parameters on the microstructure and mechanical properties of AZ91 magnesium alloy were studied. The rolling parameters of single pass 350 鈩，
本文编号：2148651
[Abstract]:Due to the urgent need of energy saving and emission reduction magnesium alloys as lightweight structural materials have been widely concerned by scholars at home and abroad in the fields of aviation automotive electronic devices and so on. In view of the low ultimate tensile strength of magnesium alloys, since last century, a large number of studies have focused on large deformation superfine grained magnesium alloys, and the strength of large deformation ultrafine grained magnesium alloys has been greatly improved compared with traditional coarse grained materials. But the elongation at room temperature is generally low. At present, researchers in metal field have prepared high strength plastic mixed crystal structure metal materials one after another. However, there is little research on the enhancement of high strength plasticity of mixed crystal magnesium alloy. In the previous research, my research group developed the (HPR) technology of large volume liner rolling. This technology is not only simple in sample preparation, less pass rolling, high efficiency, can greatly reduce the rolling cost of magnesium alloy sheet, and has a good potential for industrial application. Moreover, AZ91 magnesium alloys with excellent mechanical properties at room temperature and mixed crystal structure have been obtained by using this technique, but the control of the proportion of mixed crystals has not been fully grasped, and the formation mechanism of mixed crystals has not been clearly understood. Therefore, taking Mg-9Al-1Zn (AZ91) magnesium alloy as the research object, using HPR technology, by changing the rolling parameters (temperature, reduction, rolling pass) and recrystallization annealing parameters (temperature, time) of lining plate, different structural characteristics (size, proportion) are obtained. Texture) or fine-grained magnesium alloy, and lay a foundation for the controllable preparation of high-plasticity, simultaneous lifting, fine-grained magnesium alloy with mechanical properties comparable to that of conventional rolling but more economical and environmentally friendly. The formation mechanism of mixed crystals was also preliminarily understood. In addition, the high temperature tensile deformation behavior of mixed AZ91 magnesium alloy prepared by single pass liner rolling process was studied. The main conclusions are as follows: (1) the effects of rolling temperature and rolling parameters on the microstructure and mechanical properties of AZ91 magnesium alloy were studied. The rolling parameters of single pass 350 鈩，
本文编号：2148651
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