ZAM和Super Dyma镀锌合金体系相平衡及镀层组织研究

Both ZAM and Super Dyma are new hot-dip alloys with high corrosion resistance developed by Nisshin Steel Company and Nippon Steel Corporation. On the interface between these two kinds of alloy coating and steel substrate, the iron-aluminium inhibiting layer could not be found easily. This phenomenon has not been explained reasonably and scientifically till now. If primary MgZn2 phase and thick iron-alminium inhibtiing layer exist in the coating of ZAM and Super Dyma alloys, the formability of the galvanized steel sheet will degrade. It will be experimentally determined that the Zn-rich corner of the 450?C isothermal section phase equilibrium of Zn-Al-Mg-M(M=Fe,Si) related with ZAM and Super Dyma alloy systems using alloy equilibrium method. Through the collection of the thermo-chemical data of these systems, the thermodynamic assessment will be accomplished and their thermodynamic description will be obtained. Based on the phase equilibrium and the varying law of the activities of iron and aluminum in zinc bath,through the solidification experiment together with hot-dip and diffusion couple experiments, the effect of zinc bath temperature, galvanizing time,cooling rate and alloying elements on the solidification microstructure and the formation of iron-aluminium inhibiting layer on the interface of coating and iron substrate will be revealed. Based on the studies on the interface reaction between the steel substrate and ZAM/Super Dyma alloys, the mechanism on the thick iron-aluminum inhibiting layer not existed in the galvanized coating will be clarified. The achievements of the item will lay a solid foundation for the realization of the production of high quality steel sheet galvanized with ZAM and Super Dyma alloys in China.

ZAM和Super Dyma是日新制钢和新日铁开发的高耐蚀性镀锌合金,这两种镀锌合金正常镀层组织中不存在明显的铁-铝抑制层，至今对此没有合理的科学解释；如果这两种合金镀层中存在初晶MgZn2相和明显的的铁-铝抑制层，将严重影响镀锌钢板的成型性能。本项目采用合金法测定镀锌合金相关体系富锌角450℃等温截面的相关系，收集Zn-Al-Mg-M（M=Fe，Si）体系的热化学数据，采用CALPHAD技术进行热力学优化和评估；依据评估获得的体系相关系及锌池中铝和铁的活度变化规律，结合ZAM和Super Dyma合金在不同工艺条件下的凝固、热浸镀和扩散偶实验，揭示锌池温度、浸镀时间、冷却速度和各种合金元素等对合金镀层凝固组织和界面上铁-铝抑制层形成的影响，阐明这两种镀锌合金与钢基之间的不形成明显铁铝合金抑制层的机理。本项目的研究成果将为我国生产高质量的ZAM和Super Dyma镀锌钢板奠定坚实基础。

本项目测定了Zn-Fe-Mg、Zn-Fe-La、Zn-Al-Ti和Zn-Ti-Si三元系等温截面相关系以及Zn-Al-Mg-Fe、Zn-Al-Mg-Si和Zn-Al-Fe-Si等四元系富锌角450℃等温截面相平衡关系。依据平衡合金液相中铁和铝元素浓度及铁-铝浓度积的变化规律，对ZAM合金镀层中不形成明显铁-铝抑制层的原因进行了解释。研究了温度、铝和镁含量对锌-铝-镁合金凝固组织与力学性能的影响，在此基础上深入研究了温度、微量钛和硼以及硅对ZAM和Super Dyma镀锌合金凝固组织和力学性能的影响，并分析了这些因素对合金镀层组织的影响。通过固-液扩散偶实验，研究了磷和钛元素对镀层中铁-锌化合物形成与生长的影响，深入研究了温度和镁、锰、硅等元素对锌-铝-镁镀锌合金中铁-铝抑制层生长的影响，澄清了工艺参数和合金元素对铁-锌化合物和铁-铝抑制层生长的影响规律。开展热浸镀锌实验，分析了ZAM镀层中铁-铝抑制层的生长规律，研究了钛和硅对ZAM和Super Dyma镀层中铁-铝抑制层生长的影响，阐明了镀层中不形成明显铁-铝合金抑制层的机理。此外，还研究了温度、硅和铝含量对锌铝池中锌渣形成的影响。该项目的研究结果为ZAM和Super Dyma镀层钢板的生产工艺和质量控制奠定了理论基础。在研究期限内，培养硕士研究生7人，其中5人已经毕业。发表已标注的论文16篇，其中SCI收录9篇，EI收录6篇；授权国家发明专利5件。