Isothermal forging of aluminium based metal matrix composites reinforced with 20% Al_2O_3 particles

摘要

The aim of the present study is the investigation of the hot formability of two aluminium alloys reinforced with 20% Al_2O_3 particulate in order to develop a technology of isothermal forging for automotive components. The isothermal forging of 6061 and 2618 aluminium alloys reinforced with 20% of Al_2O_3 particles by hot torsion and hot compression tests was investigated to find out if the formability of these materials can produce defect-free components. The results were used to optimalize and individuate the optimal "processing window" in terms of temperature and strain rale following the dynamic material model. The study have analysed the constitutive equations relating flow stress, temperature and strain rales, trying to correlate the mechanical response to the microslruclure in terms of damage or microstructural changes of the malerial such as recovery, slatic and dynamic recrystallizalion, superplastic flow and phase transformations. Optical and electron microscopy (SEM) observations were performed in order to quantify the damage in terms of fracture of the particles and voids formation at the interface between the particles and the matrix. Processing maps were constructed, taking into account torsion and compression tests and the constitutive equations that correlate flow slress, strain rate and temperature in these materials. Laboratory trials were performed and final components were produced by isothermal forging to evaluate the agreement between the model and the production of the individual component. A finite element 2D and 3D code (DEFORM~(TM)) was used to model the behaviour of this malerial and lo predict all mechanical changes during isothermal deformation.