The development of high strength new Al-based alloys for structural applications using powder metallurgy

Keywords: Aluminium alloys, metal powders, powder metallurgy, compaction, sintering The aim of this study is to develop new aluminium-based powder metallurgy alloys, i.e., Al5Cu, Al5Cu0.5Mg, Al15Si5Cu2.5Mg and Al15Si5Cu2.5MgTi, as an alternative to wrought parts for use in automotive bodywork applications. Powders mixed without any admixing of lubrication or sintering aids were annealed under N2/H2 atmosphere in order to eliminate or reduce any possible thin surface oxide films. The effects of the processing parameters such as sintering and microstructure on the mechanical properties of the produced alloys were studied using high purity metal powders, such as Al and Cu produced in homeland. Alloys were prepared using Al-base powders with some other elemental metal powders mixed in a micro and/or macro level before compacting them using 3.5x13.5x3 mm3 size rectangular floating die. Compacts suitable for three point bending test were sintered at different temperature and durations under pure nitrogen atmosphere. Optimum processing parameters were defined after examining mechanical properties, phase composition, micro-structural features of the sintered compacts. It was shown that using P/M production route with a micro-alloying technique, the strength value after sintering of the base Al powder (%99.6 pure) could be increased more than five times from 84 MPa to 466 MPa with a two times higher value in hardness. At three point bending test, the mean yield strength value of 294 MPa was obtained with the elemental powder mixture of Al5Cu alloy composition. The micro-addition of Mg (0.5wt.%) have resulted in an further increase in strength value of 466 MPa with a 20% increase in hardness of Al5Cu0.5Mg.