The effect of thermomechanical processing on the tensile properties and microstructure of a 6061 Al-Al_x001B_b2_x001B_s0_x001B_b3_x001B_s metal matrix composite

摘要

This work includes a comprehensive analysis of the effect of thermomechanical processing (TMP) history on the microstructure and properties of 10 and 20 volume percent 6061 Al-Al2O3 discontinuous metal matrix composites (MMCs). Materials in which cold drawing operations were included in the TMP demonstrated increased ductilities for a given strength level when compared to samples which were processed by hot extrusion only. Microstructural analysis provided clear evidence of the absence of damage to reinforcing particles during TMP and of load transfer to these particles during subsequent straining. Failure during tension testing resulted from the ductile tearing of the matrix as voids initiated by the cracking of reinforcement particles, joined together. A distinct microstructural difference related to processing history was the development of a strongly fibered particle distribution in materials experiencing low temperature drawing operations. In order to conduct an analysis of the mechanisms by which the particles are redistributed and reoriented during processing, a channel compression die was constructed which allowed processing to be simulated by compressive straining on a mechanical testing machine. This allowed careful control of the processing parameters. An analysis of the effects of processing temperature on particle redistribution and reorientation was conducted.