Abstract
Before the task on the development of semi-solid rocker arm was performed, the fundamental research had been carried out to investigate the effects of processing parameters. AA 2014 aluminium alloys were produced by different manufacturing processes such as wrought, as spray formed, spray formed & consolidated, spray formed & extruded, continuous cast & extruded and squeeze cast in order to obtain the various initial microstructures. The wrought, as spray formed, spray formed & consolidated materials possessed non-dendritic equiaxed grains of around 18mm while the spray formed & extruded and continuous cast & extruded materials exhibited deformed and elongated grains, and squeeze cast materials consisted of approximately equiaxed dendrites. The dendrite arm spacing and grain size were around 30mm and 115mm respectively. Cylindrical specimens of the materials were compressed under the constant load at 560 (fs=0.90), 580 (fs=0.86), 600 (fs=0.78) and 610oC(fs=0.70), respectively, to obtain strain versus time curves. The as spray formed or spray formed & consolidated material showed much higher strain rates in the initial stage and greater strain at all temperatures compared to the other materials. After the fundamental research, the rocker arms were manufactured by semi-solid forming and discussed in terms of the comparison with the various processing routes such as high pressure die casting and squeeze casting. The semi-solid formed rocker arm showed better mechanical properties than any others in the hardness and static fracture test.