Relationship of Fatigue and Fracture to Microstructure and Processing in Al sub 2 0 sub 3 Fiber Reinforced Metal Matrix Composites

摘要

The tensile and fatigue properties of three matrices, including commercially pure magnesium, ZE41A (Mg-4.25Zn-0.5Zr-1.25RE), and A13Li, containing 35 vol pct FP Al2O3 fibers were studied as a function of orientation between the loading and fiber axes, matrix composition, fiber volume fraction, and fiber/matrix interfacial chemistry. It was found that the axial properties were controlled by the fiber strength, and the orientation dependence of tensile strength could be analyzed in terms of the critical strains to fracture parallel and normal to the fibers. Matrix chemistry modifications had little influence on fiber strength but significantly increased the matrix and interface strengths. A transition from fiber controlled fracture to matrix/interface controlled fracture was found as the 90 deg. As the matrix and interface strengths increased, a transition in fatigue properties were primarily controlled by the matrix and/or interface strengths. Little benefit was achieved by increasing the vol pct fibers from 35 to 55, unless the fibers were involved in the fracture process. The interfacial reaction zone was identified as MgO int he Mg-base composites and LiAl508 in the A3Li composite.