Al-Zn-Mg-Cu合金半固态成形的研究现状与应用

半固态成形技术为实现Al-Zn-Mg-Cu系高强铝合金"以铸代锻"的目标提供了有效途径。主要综述了Al-Zn-Mg-Cu合金半固态制浆与成形技术、半固态成形合金的成分调控、微观组织结构与性能等方面的研究现状与进展,同时结合笔者所在学术团队的研究经历,对半固态成形件的组织和性能进行了简要分析。详细综述了Al-Zn-Mg-Cu合金半固态制浆和成形方法,着重介绍了环缝式电磁搅拌技术、蛇形通道浇注法及复合式半固态成形技术。进而综述了Al-Zn-Mg-Cu半固态成形合金的成分及微观组织结构调控方面的研究进展,介绍了合金成分调控及热处理工艺优化对性能的积极影响,分析比较了Al-Zn-Mg-Cu合金半固态成形后的微观组织和力学性能的研究现状。最后,对该成形方向的研究和应用现状进行了总结,分析了其需要解决的主要问题,并对其发展方向进行了展望。     

半固态铸轧成形技术的最新研究

半固态加工技术具有高效、节能、近净形生产以及制成品显微组织细化均匀、机械性能好等诸多优点,是21世纪很有发展前景的一种加工方法.铸轧技术是冶金及材料领域的一项前沿技术,是将连续铸造、轧制、甚至热处理等串联为一体,铸出毫米级的薄带坯,经在线轧制后一次性形成工业产品,是短流程的先进加工技术.将高效、节能、短流程的连续铸轧技术与半固态加工技术相结合,得到半固态连续铸轧成形技术,这是一种全方位高效、节能、短流程、近终形的加工方法.文章综述了近年来半固态铸轧成形技术的研究现状,详细介绍了课题组在半固态镁合金铸轧成形技术方面所作的工作,最后预测了该技术的发展前景.     

晶粒细化对半固态Al-7%Si合金流变行为的影响

研究了化学晶粒细化对半固态亚共晶Al-7%Si合金流变行为的影响，添加细化剂为K2TiF6、
K2TiF6+石墨、K2TiF6 + Ti以及Al5TiB，采用Couette同轴圆筒式黏度计测量合金的表观黏度变化，并观
测在不同固相质量分数下试样的微观组织。实验结果表明，化学细化法可有效细化晶粒，明显改善半固态
Al-7%Si合金的流变性能，大大降低其表观黏度；Al5TiB细化效果最明显，K2TiF6 和石墨或Ti的组合较单
一的K2TiF6细化效果显著。     

Microstructure evolution of Al-Si semi-solid slurry by gas bubble stirring method

A novel technique of introducing gas bubble stirring during solidification was studied to prepare Al-Si semi-solid slurry. The microstructure evolution of the slurry during slow cooling process after stirring was investigated. The effects of the solidification rate on the microstructure of the semi-solid slurry were investigated under three different solidification conditions. The results show that fine non-dendritic slurry can be obtained using the gas bubble stirring method. Ripening and coarsening of primary Al grains are observed during the slow cooling process, and at last coarsened eutectic Si appears. Primary Al grains with different sizes and eutectic Si are obtained, corresponding to three different solidification rates.     

Microstructural morphology of the semi-solid high carbon steel T12 before and after rheo-rolling

The semi-solid high carbon steel T12 was rolled in a closed box groove under a certain condition by the rheo-rolling equipment, and the microstructural morphology of the semi-solid T12 before and after deformation was investigated by optical microscope to analyze and summarize the microstructure evolution law of T12 deformed in semi-solid state. The experiment results show that the grain shape before deformation of the semi-solid T12 steel displays globule or ellipse by the electromagnetic stirring,the distribution of solid and liquid phases is homogeneous. But the microstructure of semi-solid product after rheo-rolling exhibits macrosegregation that the distribution of liquid and solid phases changes, the liquid phases divorce from the solid phases. In the transverse section, most of the solid phases get together in the center of the specimen, the liquid phases flow to the surface or the edge of the specimen, and the grains occur plastic deformation while reduction increased. In longitudinal section, the middle microstructure of the specimen is more homogeneous than that at the head or tail, the head microstructure is similar to the tail and the size of the grains is not homogeneous.     

Preparation of semi-solid aluminum alloy slurry poured through a water-cooled serpentine channel

A water-cooled serpentine channel pouring process was invented to produce semi-solid A356 aluminum alloy slurry for rheocasting, and the effects of pouring temperature and circulating cooling water flux on the microstructure of the slurry were investigated. The results show that at the pouring temperature of 640-680°C and the circulating cooling water flux of 0.9 m3/h, the semi-solid A356 aluminum alloy slurry with spherical primary α(Al) grains can be obtained, whose shape factors are between 0.78 and 0.86 and the grain diameter can reach 48-68 μm. When the pouring temperatures are at 660-680°C, only a very thin solidified shell remains inside the serpentine channel and can be removed easily. When the serpentine channel is cooled with circulating water, the microstructure of the semi-solid slurry can be improved, and the serpentine channel is quickly cooled to room temperature after the completion of one pouring. In terms of the productivity of the special equipment, the water-cooled serpentine channel is economical and efficient.     

半固态专用铝合金AlSi6Mg2微合金化研究

半固态加工是一种新的近终成形技术，但由于缺乏适合发挥其优势的专用合金，使这项技术在工业中的推广应用受到了限制，针对这一现状开发新型铝合金AlSi6Mg2。利用电磁搅拌装置制备半固态浆料，探讨了微量合金化元素Ti，Sr对AlSi6Mg2半固态合金微观组织和力学性能的影响。结果显示，合金中Ti含量为0．08％左右时，能够细化初生相α（Al）基体；合金中Sr含量为0．02％～0．04％时，不仅能够改善共晶硅形貌，使其由板条状转化为点状或短簇状，而且对Mg2Si也有一定的变质作用，使合金的性能明显改善，特别是塑性提高了1倍以上。     

SiCp/2024 复合材料半固态坯二次加热组织的研究

研究了用于触变成形的SiCp/2024复合材料的二次加热组织及其影响因素。结果表明，对SiCp/2024复合材料的二次加热中最佳工艺参数为：重熔温度在590－600℃之间，保温时间为5－10min.SiCp/2024复合材料在局部重熔过程中具有较高的稳定性，随温度的提高和保温时间的增加，球形固相颗粒尺寸增加很小。5％SiCp/2024复合材料在590℃时的晶粒粗化速率常数为27.45μm^3/s,15%SiCp/2024复合材料和25％SiCp/2024复合材料在590℃时的晶粒粗化速率常数分别为12.54μm^3/s和6.89μm^3/s，均小于基体合金的晶粒粗化速率常数59.56μm^3/s。     

SiCp/A356复合材料非真空半固态搅拌钎焊研究

研究了SiCp/A356复合材料非真空半固态搅拌钎焊过程。在一定的搅拌钎焊条件下,重点研究了钎料的固相率对接头的微观结构、线结合率和强度的影响规律。研究结果表明:在搅拌条件下,半固态钎料固相率对基体氧化膜的破碎有重要影响;随着钎料固相率的增加,接头界面的线结合率和接头的强度先增加后减小;在钎料固相率为60%时,接头界面线结合率和接头强度同时达到最大值,分别为91.2%和160MPa。