MECHANISM OF DUCTILE FRACTURE IN AN FE-21 PERCENT CR-0.05 PERCENT C ALLOY

The mechanics of ductile fracture of an Fe-21 % Cr-0.06% C alloy have been studied in the temperature range 20-600°C. This alloy contains a dispersion of small (0.1-3 μ) carbide particles, larger manganese sulphide inclusions, and moreover exhibits dynamic strain-ageing properties which result in an inhomogeneous strain distribution. Voids are initiated at all temperatures by decohesion of both the carbide/matrix and inclusion/matrix interfaces. At 400°C to 500°C when local solute depletion causes intense shear on planes inclined at 45° to the tensile axis, the inhomogeneous strain distribution causes rapid void growth along these planes resulting in slip off" and a low ductility fracture. © 1968."