摘要
针对传统热轧制备镁/铝合金复合板大下压率复合时异种金属协调变形差、界面氧化膜去除困难和金属间化合物层(Intermetallic compounds,IMCs)生成不易控制的问题,提出采用高频脉冲电流辅助一步轧焊成形制备镁/铝合金复合板的新方法。探讨30 kHz、400 A、50%占空比的脉冲电流通电120 s作用,不同压下率复合板界面的结构形貌及结合强度。结果表明:压下率为16.8%时,复合板剪切强度最高,达到27.87MPa;不同压下率复合板横截面界面处均出现不同程度的熔融液相金属液珠挤出的现象,当压下率较小时(压下率为16.8%和22.3%)界面IMCs较厚,约为7.8μm,且界面呈现明显的“齿状”结构形貌;随着压下率的增大,IMCs逐渐减薄且界面形貌趋于平直。综合分析发现,高频脉冲电流辅助作用可实现镁/铝合金复合板的小压下率复合;其界面结合机理可归纳如下:镁/铝合金连接界面局部高温导致的界面微区部分母材金属熔化的熔钎焊接和原子扩散连接的冶金结合机理。分析其原因主要是连接界面微区局部高温并超过Mg-Al相图共晶温度形成的共晶液相,而界面局部高温一方面是异种金属连接界面待复合微区的局部接触电阻增大导致的瞬时高温;另一方面是高频脉冲电流在待连接界面微区的集肤和邻近效应导致的。
In order to solve the problems that poor coordinated deformation of the dissimilar composite metal with large rolling reduction,difficulty in removing the interfacial oxide film and controlling the formation of intermetallic compounds(IMCs)in the fabrication process of Magnesium/Aluminum alloy composite plate by traditional hot rolling,a new method of rolling-welding process assisted by high-frequency pulse current is proposed for preparing magnesium/aluminum alloy composite plates.The interfacial morphologies and bonding strength of the composite plate are investigated under pulse current of 30 kHz,400 A and 50%duty cycle that was loaded for 120 s with the different rolling reduction parameters.The results show that the shear strength of composite plate is the highest and up to 27.87 MPa when the rolling reduction is 16.8%.In addition,different degrees of molten liquid metals are extruded at the bonding interface in various rolling reduction.The IMCs transition layer is thick and reaches to 7.8μm,and the interfacial morphology presents an obvious“toothed”structure when the rolling reduction is low(the rolling reductions are 16.8%and 22.3%).Accompanied by increasing of the rolling reduction,the thinner IMCs layers are reserved at the interface and also a flat interface is obtained.Comprehensive analysis shows that the Magnesium/Aluminum alloy composite plates can be fabricated by a low rolling reduction with the assistance of high-frequency pulse current,and the interfacial bonding mechanism can be summarized as follows:the metallurgical bonding mechanism of local high temperature at the bonding interface of Magnesium/Aluminum leads to part of base metal molten brazing and mutual atomic diffusion bonding.This can be contributed to the local high temperature of the bonding interface and exceeds the eutectic phase of the Mg-Al phase diagram above the eutectic point.On the one hand,the local temperature rise is due to an increase in contact resistance at the bonding interface.On the other hand,localized high temperatures are caused by skin-setting effects the skin and adjacent effects of high-frequency pulse current.
作者
张婷婷
许振波
王艳
卞功波
王涛
王文先
ZHANG Tingting;XU Zhenbo;WANG Yan;BIAN Gongbo;WANG Tao;WANG Wenxian(College of Mechanical and Vehicle Engineering,Taiyuan University of Technology,Taiyuan 030024;Engineering Research Center of Advanced Metal Composites Forming Technology and Equipment,Ministry of Education,Taiyuan University of Technology,Taiyuan 030024;College of Material Science and Engineering,Taiyuan University of Technology,Taiyuan 030024)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2024年第4期305-315,共11页
Journal of Mechanical Engineering
基金
国家自然科学基金资助项目(51805359,52075360)。
关键词
镁/铝合金复合板
高频脉冲电流
轧焊复合成形
部分母材金属熔化
冶金结合机理
Mg/Al alloy composite plate
high frequency pulse current
rolling-welding composite forming
localized metal melting
metallurgical bonding mechanism
