高强钢/镁合金异质材料车身激光-电弧复合拼焊技术应用基础研究

To obtain high-strength steel/magnesium (Mg) alloy tailor welded blanks for the demand of high-reliability and high-efficiency tailor-welding technology, this project proposes “nano-metallic compound-base solid solution + Fe-base solid solution” interface design between high-strength steel and Mg alloy at high interfacial reaction temperature and proposes a new idea for plastic toughness strengthening, aiming at the bottleneck problem of poor plastic toughness of welded joints caused by hard and brittle metallic compounds at high-strength steel/Mg alloy interface. The formation conditions and metallurgical mechanism of “double solid solution interface” between Mg/steel are clarified by studying the formation law of Mg/steel laser-arc hybrid butt-fusion welding, the behavior of element diffusion, reaction and phase precipitation at high interface reaction temperature. The performance enhancement mechanism of Mg/steel “dual solid solution” joints is revealed by analyzing and verifying the effect of lattice distortion on the interface plasticity and toughness, and by explaining the matching mode between lattice distortion and Mg/steel matrix interface. Based on the above research, this project develops high-strength steel/Mg alloy heterogeneous metal laser-arc hybrid tailor-welding technology and its matching welding materials, which would provide theoretical and technical support for the design and manufacture of high-strength steel/Mg alloy body tailor welded blank parts.

以车身高强钢/镁合金拼焊板制备对高可靠高效拼焊技术需求为牵引，针对高强钢/镁合金界面硬脆金属化合物导致焊接接头塑韧性差的瓶颈难题，本项目提出高界面反应温度下高强钢/镁合金“纳米金属化合物基固溶体+Fe基固溶体”界面设计及塑韧性强化新思路。通过研究钢/镁激光-电弧复合对接焊焊缝成形规律，高界面反应温度条件下元素的扩散、反应以及相析出行为，阐明镁/钢“双固溶体界面”形成条件及冶金机理；通过分析和验证晶格畸变效应对界面层自身塑韧性及其与钢/镁基体界面匹配模式的影响，揭示镁/钢“双固溶体”焊接接头的强韧化机制。在上述研究基础上，开发出高强钢/镁合金异质材料激光-电弧复合拼焊技术及配套焊接材料，为高强钢/镁合金车身拼焊板零部件设计和制造提供理论和技术支撑。

针对高强钢/镁合金界面硬脆金属化合物导致焊接接头塑韧性差的瓶颈难题，原创提出基于高界面反应温度的高强钢/镁合金“纳米金属化合物基固溶体+Fe基固溶体”界面设计及塑韧性强化新思路，开发出脉冲激光诱导电弧热源能量密度和能量梯度的精确调控方法，发明了高界面反应温度高强钢/镁合金激光诱导电弧熔化焊技术，解决了焊接过程中钢基体瞬时熔化（峰值2249℃）与镁合金熔池（沸点约1100℃）稳定共存的工艺难题，提出了稳定焊接成形条件，实现高强钢/镁合金对接熔化焊接头拉伸强度从镁合金母材的50%提高到95%以上，为国内外报导的最高值，使高强钢/镁合金异种金属焊接结构的工业应用成为可能。.通过利用双聚焦离子束、高分辨透射电镜、边-边匹配模型和O点阵模型以及第一性原理计算等方法和手段，阐明了“双固溶体”界面层的热力学形成条件、生长机制（冶金机理）及合金化元素选择判据，发现并揭示了双固溶体界面存在的自适应晶格畸变效应，首次获得具有共格匹配的镁/钢对接熔化焊接头，创建了高强钢/镁合金对接熔化焊界面强韧化理论，解决了高强钢/镁合金焊接界面从“硬脆金属间化合物”向“双固溶体”以及界面层与母材从“非共格”向“共格匹配”跨越的两大瓶颈难题。.项目执行期间，通过与中国第一汽车集团股份有限公司合作，设计并制备出高强钢/镁合金车门内板典型结构件样件；通过与华为合作，开发出了笔记本电脑转轴以及键盘支架等典型不锈钢/镁合金异种金属焊接结构样件，展现出了广阔的应用前景。.在本领域高水平学术期刊发表学术论文16篇，其中被SCI检索11篇、被EI检索16篇；已获授权发明专利7项、公开发明专利8项，其中获得日本授权发明专利1项，申请美国发明专利2项；获得中国专利奖银奖1项；作为承办单位连续三年主办焊接国际论坛会议（2020-2022），连续两年被评为中国机械工程学会“最具学术影响力会议”称号；通过本项目研究工作，培养博士研究生2人，硕士研究生6人。