Effect of the aspect ratio of whisker on work hardening rate of as forged 2024Al/Al18B4O33w composite

The 2024Al/Al(18)B(4)O(33)w composite fabricated by the squeeze casting technique is forged with different deformation levels to improve tensile properties. The work hardening rates of 2024Al/Al(18)B(4)O(33)w composite with different forging deformation levels are studied. The results show that the forging process plays a very important role in work hardening rate due to the reduction in the aspect ratios of whiskers and the increase in the dislocation density and the angle between whisker axis and forging direction with increasing deformation level. The variations of work hardening rates in the microscopic yield stage, yield stage and macro plastic stage are correlated with the variation of the aspect ratio of whisker. The initial work hardening rate is higher then rapidly decreases due to the more favorable for annihilation than multiplication of the initial stored dislocations. The work hardening rate of the forged 2024Al/Al(18)B(4)O(33)w composite at the deformation level of 70% with the highest initial stored dislocation density is the highest in the microscopic yield stage and macro plastic stage, but is the lowest in the yield stage due to the interaction of dislocations. The work hardening exponent increases with decreasing the aspect ratio of whiskers. The cracked and progressive cracking whiskers have an impact on work hardening capacity. (C) 2015 Elsevier Inc. All rights reserved.