Characterisation and Modelling of Intermetallic Phase Growth of Aluminium and Titanium in a Tailored Forming Process Chain

The combination of aluminium (AlSi₁MgMn) and titanium (Ti6Al6-4V) allows producing components with high lightweight potential and at the same time high strength and chemical resistance. Upon joining of dissimilar materials, intermetallic phases (IMP) can form. These are comparatively hard and brittle and represent a weak point in the hybrid component. Along the process chain for manufacturing a hybrid bearing bushing made of AlSi₁MgMn and Ti6Al-4V by co-extrusion, die forging and heat treatment, the joining zone is exposed to high thermal loads. As a result, the individual process steps can lead to the growth of IMP reducing the compound’s quality. In order to investigate the formation and the growth of IMP at process-relevant temperatures and contact times in detail, experimental analogy tests were carried out. Subsequently, the specimens were examined by scanning electron microscopy. Due to the constant temperature and the respective contact time, the diffusion coefficient was calculated from the determined phase thickness using the Einstein-Smoluchowski equation. This allowed describing the diffusion coefficients as a function of temperature and implementing them into a finite element model via a subroutine. To validate the subroutine, further tests were carried out and the calculated phase thickness was validated with experimentally determined phase thickness, which exhibited good correlation.