Influence of heat cycle and degree of dilution in electron beam welding on the properties and the long-time behaviour of aluminium copper dissimilar material joints in current-carrying parts

轻量化结构的巨大潜力，尤其是在电动汽车领域，在于用铝替代铜。此外，可以应用铝作为导体和铜作为接触材料（牢固地接合）。到目前为止，现有技术仅将焦点放在裂纹敏感金属间相（IPS）的识别上。除IPS外，接头的较大部分由Al-Cu混合晶体组成，其类似于EN-AW-2xxx合金，如已进行的试验所示。通过验证，可以将2xxx合金的已知电气和机械性能转移到异种材料接头上。可以预期，混晶的形成导致强度的增加，但同时导致电导率的降低。外部影响因素如温度、电流和时间等通过扩散和电迁移引起连接区结构的变化。此外，将发生异种材料接头的工艺性能的时间变化（电阻增加，强度降低）。关于这种行为的调查结果将允许得出有关接头预期寿命的结论。该研究项目的目的是实现对材料结合铝/铜异种材料接头的发展，结构和时间变化（通过电操作）的全面理解。电子束焊接的异常快速和精确的束操纵允许实现特定的温度-时间序列和稀释度。这样，在焊接过程中，IPS将在不需要的相（例如具有更高的延展性或导电性）的组成和形成方面受到影响。将尝试在相反参数（强度和电导率）之间设定预期使用寿命的最佳值。

A great potential for light-weight construction, above all in the field of electro-mobility, lies in the substitution of copper by aluminium. It is, moreover, possible to apply aluminium as a conductor and copper as a contact material (firmly bonded joining). The state of the art, so far, has put the focus only on the identification of the crack-sensitive intermetallic phase (IPS). Besides the IPS, the larger part of the joint consists of an Al-Cu mixed crystal which is similar to an EN-AW-2xxx alloy, as suggested by the tests which have been carried out. A verification of this allows the transfer of the known electric and mechanical properties of 2xxx alloys to the dissimilar material joint. It is expected that the mixed crystal formation leads to the increase of strength but, at the sime time, to a reduction of the electric conductivity. External influential factors, such as temperature, currentfeed and time bring about the change of the joining zone structure by diffusion and electro-migration. Moreover, a temporal change of the technological properties (increase of the electric resistance, reduction of strength) of the dissimilar material joint will occur. Findings about this behaviour will allow to draw conclusions about the expected lifetime of the joints.The aim of the research project is to achieve overall comprehension about develoment, structure and temporal changes (by electric operation) of the material-binding aluminium / copper dissimilar material joints. The exceptionally fast and precise beam manipulation of electron beam welding allows to achieve specific temperature-time sequences and dilution degrees. This way, the IPS shall be influenced during the welding process with regard to compositon and formation of unrequired phases (for example with higher ductility or electric conductivity). An attempt will be made to set the optimum for the expected service life between the opposedparameters (strength and electric conductivity).