【作者】 朱波；

【导师】 梁伟；

【作者基本信息】 太原理工大学 ， 材料加工工程， 2011， 硕士

【摘要】 镁及镁合金耐蚀性差是限制其广泛应用的主要原因之一。相比之下,铝及铝合金通常具有很好的耐蚀性能和塑性成形性能,具有表面可修复性、可修饰性,铝也是镁合金中应用最多的一种对耐蚀性改善有益的合金元素。因此,在镁合金表面覆盖一层耐蚀性好的铝合金形成叠层复合材料,则可以在保护镁合金的同时又能发挥镁合金比强度和比刚度高、减震性能和电磁屏蔽性能好等的优点。本文通过热压法在大气环境下采用镁铝共晶合金粉末(Mg-31at.%Al)和铝镁共晶合金粉末(Mg-62at.%Al)作为中间层(钎料),热压压头温度分别在460℃、480℃和480℃、500℃下,施加30 MPa压力,保压1min,成功制备了100mmx 100mm×2.4mm的AZ31B/Al复合板。X射线无损检测表明镁铝复合板层界面完整,无气孔、未熔合等缺陷。利用扫描电镜(SEM)和能谱仪(EDS)观察分析了不同工艺参数下所制备的镁铝复合板的层界面微观组织结构。结果表明：热压过程中,中间层(钎料)与两侧基体均发生明显的扩散,层界面通过扩散形成冶金结合。在采用镁铝共晶合金粉末制备的镁铝复合板的层界面上,从AZ31B镁合金板到1050纯铝板依次形成α-Mg+Mg17Al12双相层、Mg17Al12单相层和Mg2Al3单相层；在采用铝镁共晶合金粉末制备的镁铝复合板的层界面上,从AZ31B镁合金板到1050纯铝板依次形成Mg17Al12单相层和Mg2Al3单相层。采用粘接拉伸法,测试了镁铝复合板层界面的结合强度,并利用扫描电镜和X射线衍射仪观察和分析了断面的组织形貌和物相组成。结果表明：镁铝复合板的层界面结合强度可达24 MPa,层界面沿较厚的单相金属间化合物层开裂。镁铝复合板层界面处较厚的镁铝金属间化合物层,尤其是Mg2Al3层,是层界面的薄弱位置。采用α-Mg+Mg17Al12共晶合金比采用α-Al+Mg2Al3共晶合金作钎料利于减小Mg2Al3层的厚度,界面结合强度也相对提高。电化学腐蚀结果表明：镁铝复合板的耐蚀性较镁合金基体有很大的提高。在3.5wt.%NaCl溶液中,腐蚀电流从AZ31B的10.75μA/cm2降低至8.68×10-3μA/cm2,与纯Al板的相当。采用锌板中间层,压头温度440℃,热压30s,压强15MP持续60s制备AZ31B/Zn/Al复合板,中间层与镁合金基体反应剧烈,而与铝基体无明显反应和扩散。中间层与铝结合为机械咬合结合强度小更多还原

【Abstract】 Poor corrosion resistance of magnesium and magnesium alloys is one of the main reasons that prevents them from wider applications in many fields. In contrast, aluminum and aluminum alloys have excellent corrosion resistance and plastic formability. Their surface can be self-repaired and paintable, and Al element is beneficial for the corrosion resistance of Magnesium. Thus, coating Mg alloy with Al on its surface can fabricate a kind of laminated composite plate that can not only protect Magnesium alloys from corrosion but also maintain the magnesium alloys’high specific strength and specific stiffness, excellent damping performance as well as electromagnetic shielding characteristics.In this paper, a composite plate of magnesium alloy (AZ31B) and a pure aluminum metal with the size of 100mm×100mm×2.4mm was produced successfully by using two kinds of Mg-Al eutectic alloys (Mg-62at.%Al and Mg-31at.%Al) as the solder, respectively, and hot pressing with the indenter at different temperatures 460℃,480℃and 480℃,500℃, respectively, under 30 MPa for 60s in atmosphere.X-ray nondestructive test indicates that bonding interface is integrity. No pore and incomplete fusion were detected. The scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrscope (EDS) was used for observing the cross-sectional micro structures and analysing the components of the bonding interface of the specimens fabricated under different process parameters. The results show that obvious diffusion occurs between the solders and the base plates, and a metallurgical bonding was achieved. When using Mg-Al eutectic alloy powder as solder, laminated interface of composite plate is composed of a-Mg+Mg17Al12 two-phase layer, Mg17Al12 single phase layer and Mg2Al3 single phase layer consecutively from AZ31B substrate to 1050 substrate, while when using Al-Mg eutectic alloy powder as solder, the laminated interface is composed of Mg17Al12 single phase layer and Mg2Al3 single phase layer consecutively from AZ31B substrate to 1050 substrate.The bonding strength was tested by tensile test, and the fracture surface was analyzed by SEM and X-Ray diffractomer (XRD). The interface strength as high as 24 MPa was obtained, and it was indicated that the fracture always occurs in a thicker intermetallics layer. The thick intermetallic compound layer in the laminated interface, especially, the Al3Mg2 layer is the weak link of the bonding where fracture is prone to occur. Mg2Al3 layer is thinner when using a-Mg+Mg17Al12 eutectic alloy as solder than that when using a-Al+Mg2Al3 eutectic alloy, and the interface bonding strength is relatively higher. Electrochemical tests show that corrosion resistance of Mg-Al composite plate is greatly improved compared to that of Mg alloys. The corrosion current of Mg-Al composite plate is same to that of the pure Al in 3.5wt.% NaCl solution.Besides, AZ31B-Zn-Al composite plate was fabricated using Zn plate as the interlayer (solder) with the hot indenter heated at 440℃holding for 30 s and under pressure of 15MPa lasted for 60 s. It was found that a violent reaction occurred between the interlayer and AZ31B substrate, but no reaction occurred on the side of the Al substrate. In this case, the plates was mechanically bonded and the bonding strength was much lower.更多还原