Effect of Extrusion Temperature on Fabrication of C_(sf)/Mg Composite by Extrusion Directly Following Vacuum Pressure Infiltration Process

Csf/Mg composites are fabricated by extrusion directly following vacuum pressure infiltration technique,the effect of extrusion temperature on the deformation law,formability and microstructure of the composites are investigated,the causes of hot cracking are analyzed.In the range of 380-420 ℃,with the increasing extrusion temperature,the maximal forming pressure decreases gradually and the steady extrusion stage shorts in the extrusion pressure-displacement curves.At lower extrusion temperature,many macro cracks occur at the front end and carbon fibers are broken severe.The fiber breakage rate decreases with increasing extrusion temperature,but overhigh extrusion temperature may lead to hot cracks on the surface of composite bars,and the hot cracks become severe along the extrusion direction.Temperature rise due to plastic deformation is the main reason for the hot cracks on the composite surface.The matching between the extrusion temperature and alloy solidification rate is an efficient way to minimize the risk of the hot cracking.With extrusion temperature ranging from 390 ℃ to 400 ℃,extrusion speed of 2-3 mm/s,Csf/Mg composites with high quality are obtained.