NOTCHED BEHAVIOR OF A SILICON-CARBIDE PARTICULATE-REINFORCED ALUMINUM-ALLOY MATRIX COMPOSITE

The notched fatigue behaviour of a fine particulate reinforced Al-Cu-M g (2124) matrix composite is compared with that of an equivalent monol ithic alloy (2024), both in the T4 condition. The difference in respon se of the materials for tensile and fatigue loading is pronounced. Und er tensile loading the composite exhibits 'notch weakening' and an alm ost brittle fracture, while the monolithic alloy shows a degree of 'no tch strengthening'. In contrast, under fatigue loading the composite e xhibits a much smaller notch sensitivity than that of the monolithic a lloy. At 10(7) cycles the fatigue notch sensitivity factor is reduced by approximate to 6.5. The notched tensile behaviour of the composite is interpreted in terms of its reduced ductility and susceptibility to cavitation. Conventional notch theory is able to account for the notc h sensitivity of the monolithic alloy in fatigue, but not the composit e.