Generation of a fine-grained microstructure in GMA-welded aluminium by modified filler materials for a reduction of solification cracks

研究项目的目的是在gma焊接过程中，将铝合金凝固过程中某些元素的晶粒细化效应转移到焊缝金属上。通过在焊丝上涂覆成核元素，如钛，它们被输送到焊缝金属中，从而有助于晶粒细化。由于焊缝金属中形成了细小的晶粒，因此有可能显著减少凝固裂纹。此外，还将研究晶粒细化是否可以转移到自硬化和极热裂敏感合金类型。此外，为了对焊接金属的机械强度产生积极的影响，并且通过现在更强的焊接金属的支撑作用部分补偿热影响区的强度下降，焊接材料的硬化是要实现的。利用金属-玻璃技术研究焊缝金属中涂层元素的成核机理。这使得熔体的实际冻结状态成为可能，并且通过能量色散x射线辐射在扫描电子显微镜中可以看到凝固核的分布。该技术旨在扩展铝材料gma焊接过程中焊缝金属形成的知识水平。除了涂层元素之外，由于焊接过程而产生的其他凝固核也可以被看到。进一步的目的是推导出在改性填充材料上晶粒细化元素层在焊缝金属中形成微观组织的函数关系。在这里，晶粒尺寸、机械性能、涂层厚度和/或成分之间的一般关系将得到发展。作为研究的副产品，可以确定涂层对焊接过程的影响。这包括对弧长、液滴过渡和渗透行为的影响。这里也力求推导出一般原则。

The aim of the research project is to transfer the known grain-refining effect of certain elements during the solidification of aluminum alloys onto the weld metal during GMA-welding. By the coating of the welding wires with nuclei-forming elements, such as titanium, they are transported into the weld metal and thus contribute to grain refinement. Due to the fine grain formation in the weld metal, it is possible to significantly reduce solidification cracks. Furthermore, it will be investigated whether the grain refinement can be transferred to the self-hardening and extremely hot-crack-sensitive alloy types. In addition, a hardening of the weld material is to be realized in order to achieve a positive effect on the mechanical strength of the weld metal and partly to compensate the strength drop in the heat-affected zone by a supporting effect of the now stronger weld metal.The metal-glass technology is to be used to investigate the nucleation mechanisms of the coating elements in the weld metal. This makes it possible to virtually freeze the state of the melt and to make the distribution of the solidification nuclei visible in the scanning electron microscope by means of energy-dispersive X-ray radiation. This technology is intended to extend the level of knowledge about the formation of the weld metal during the GMA-welding of aluminum materials. In addition to the coating elements, other solidification nuclei occurring as a result of the welding process can also be made visible as well. A further object is the derivation of functional relationships for the formation of the micro-structure in the weld metal by the layer of grain-refining elements on the modified filler materials. Here, general relationships between grain size, mechanical properties, coating thickness and / or composition are to be developed.As a by-product of the investigations, the influence of the coatings on the welding process can be determined. This includes the influence on the arc length, the droplet transition and the penetration behavior. Here, too, the derivation of general principles is striven for.