Paper number 134

FRACTURE SURFACES OF AL2O3/AL-ALLOY COMPOSITES

Xicong Liu and Yue Zhuo

Department of Materials Engineering and Applied Chemistry,
National University of Defense Technology, 410073, Changsha, Hunan, P. R. of China

Summary

After tension, creep, fatigue and fracture toughness tests for Al2O3 short fibers reinforced two Al-alloy composites, Al2O3/Al-7Si-0.6Mg and Al2O3/Al-5Si-3Cu-1Mg, the fracture surfaces were studied. Macroscopically, fracture surfaces for the two composites were very different and dominated by the plasticity of matrix at the test conditions. Microscopically, dimples existed in two matrixes fractured, which showed ductile rupture features. Plastic deformation zone near cracks in Al2O3/Al-7Si-0.6Mg composite was much larger than that in Al2O3/Al-5Si-3Cu-1Mg composite. Fatigue striation loops in fracture surfaces indicated that fatigue crack propagation in the composites was made by linking striation loops around each broken fiber. Few broken fibers can be observed in the fracture surfaces for the tensile specimens ruptured at temperatures above 300 oC, in which almost all broken fibers were deeply embedded into the matrix in shape of sleeve.

Keywords

Al2O3/Al-alloy composite, fractography, fatigue, creep, tension, fracture toughness, plastic deformation, material damage