利用挤压加工制备铝包镁复合板材研究

发布时间：2018-07-23 10:43

【摘要】：Mg/Al复合板材结合了镁合金密度小、比强度、比刚度高、减震性好,具有广泛的应用前景。本论文基于现有的复合板材制备技术,创新性的设计提出利用挤压加工制备多层复合Mg/Al板材,并利用累积挤压(AEB)制备了层数更多的Mg/Al复合板材。利用先进的EBSD等微观表征分析手段、光学显微镜、XRD、扫描电镜等方法进行相应系统的研究了挤压加工对于复合板材不同组元金属的微观组织以及织构的变化规律。不同退火制度对界面和微观组织的影响规律及Al外层约束对Mg层轧制变形能力和组织的影响也被系统研究,本论文研究结果表明:①通过挤压成功制备了AZ31/6082复合板材,初次挤压的板材还可以作为原料进行再次挤压,实现累积挤压加工。初次挤压镁合金中含有大量细小再结晶晶粒和少量变形组织,铝合金的晶粒呈现典型的带状结构,且周围有很多细小再结晶晶粒。经过再次挤压加工板材中镁合金和铝合金组织均匀性获得提高,但晶粒没有出现细化。各种板材随着退火时间的延长,晶粒组织呈等轴状均匀分布,随着退火温度增加,晶粒发生显著的粗化。②AZ31/6082复合板材在挤压过程中,Mg层的厚度和Al层的厚度随着层数的增加而变薄,且界面结合情况良好,表现出不同厚度的界面结合层。AEB制备的复合板材没有出现明显的颈缩现象,也没有出现明显的“波浪”状结构。再次挤压,过渡层厚度从几微米增加到20微米左右。靠近Al层的为Mg2Al3,且Mg2Al3比Mg17Al12厚。随温度升高,界面过渡层厚度显著增加,当退火温度达到450°C,界面发生熔化,长时间退火导致材料整体烧蚀。当温度较高时,界面厚度快速变化,且有利于Mg2Al3的生长。③复合板中Mg合金主要形成{0001}10-10织构,而Al合金以“Copper”“S”“Brass”织构为主,内外层织构组分有一定的差异,但差异较小。镁合金主要形成典型挤压织构,基轴与挤压方向垂直,但表层与内层织构有显著不同。表层镁主要基轴主要集中在ND附近,柱面呈现随机分布。而内层镁基轴呈现双峰,双峰沿TD方向倾转约14度,且柱面呈现一定的择优分布。④通过挤压复合后的AZ31轧制性能得到提高,压下量为40%。由于初始晶粒尺寸较小,即使20%应变量也未发现显著的孪生变形。P1复合板材中Mg合金织构为典型{0001}基面织构,经过轧制后形成{0001}10-10织构。且随着轧制量的增大织构强度下降,未约束条件下比约束条件下形成的织构强度高。
[Abstract]:Mg / Al composite plate combines magnesium alloy with low density, high specific strength, high specific stiffness and good shock absorption, and has a wide application prospect. In this paper, based on the existing composite plate preparation technology, the innovative design proposed to use extrusion processing to prepare multi-layer composite mg / Al plate, and the cumulative extrusion (AEB) was used to prepare more layers of mg / Al composite plate. The changes of microstructure and texture of different component metals in composite sheet were studied systematically by means of advanced EBSD, optical microscope XRD, scanning electron microscope and so on. The effect of different annealing conditions on interface and microstructure and the effect of Al outer layer confinement on rolling deformation ability and microstructure of mg layer have also been systematically studied. The results show that AZ31 / 6082 composite sheet was prepared successfully by extrusion. The plate extruded for the first time can be extruded again as raw material to realize accumulative extrusion processing. There are a lot of fine recrystallized grains and a small amount of deformed microstructure in the first extrusion magnesium alloy. The grains of aluminum alloy show typical banded structure and there are many fine recrystallized grains around them. The microstructure uniformity of magnesium alloy and aluminum alloy was improved after reextrusion, but the grain size was not refined. With the increase of annealing time, the grain structure of all kinds of plates is equiaxed and uniformly distributed, and with the increase of annealing temperature, During extrusion, the thickness of mg layer and Al layer become thinner with the increase of the number of layers, and the interface bonding condition is good. It shows that there is no obvious necking phenomenon and no "wavy" structure in the composite plate prepared with different thickness interfacial bonding layer. AEB. Once again, the thickness of the transition layer increases from several microns to about 20 microns. Mg2Al3 is closer to Al layer, and Mg2Al3 is thicker than Mg17Al12. With the increase of temperature, the thickness of the interfacial transition layer increases significantly. When the annealing temperature reaches 450 掳C, the interface will melt and the whole material will be ablated after long annealing. When the temperature is high, the interface thickness changes rapidly, and the mg alloy mainly forms {0001} 10-10 texture in Mg2Al3 composite plate, while Al alloy is mainly "Copper" S "Brass" texture. But the difference is small. The typical extrusion texture of magnesium alloy is formed, the base axis is perpendicular to the extrusion direction, but the texture of surface layer and inner layer is obviously different. The main base axis of surface magnesium is mainly located near ND, and the cylindrical surface is randomly distributed. However, the inner magnesium base axis presents a double peak, the double peak tilts about 14 degrees along the TD direction, and the cylinder presents a certain preferential distribution. 4. The rolling performance of AZ31 is improved by extrusion compounding, and the reduction is 40. Because the initial grain size is small, no significant twinning deformation. P1 composite sheet mg alloy texture is found, and the {0001} 10-10 texture is formed after rolling. With the increase of rolling amount, the texture strength decreases, and the texture strength under unconstrained condition is higher than that under constraint condition.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG376;TB331

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