Hot hardness and indentation creep study on Al–5% Mg alloy matrix–B4C particle reinforced composites

Al–5% Mg matrix composites reinforced with 10 and 20% B4C were prepared by stir casting method. Microhardness of unreinforced alloy and composites were measured using a Nikon hot hardness tester. It was observed that hardness values decrease gradually with increase in temperature. Transition temperature increases marginally from 262 to 274 °C due to addition of 20% B4C. Stress exponent for all the materials varies from 4.3 to 4.5 at temperatures in the range 310 and 370 °C. Apparent activation energy for creep increases with increase in B4C content. At temperatures below transition temperature, deformation is attributed to the increased interatomic spacing due to increase in temperature and the unpinning of attractive junction between glide and forest dislocations. At temperatures above the transition temperature, deformation is diffusion assisted phenomenon such as dislocation glide and dislocation climb.