Fracture mechanics properties and failure mechanisms of environmental-friendly brass alloys under impact, cyclic and monotonic loading conditions

Final heat treatment was applied for the microstructural modification and machinability improvement of Pb-free brass alloys, namely CW510L and CW511L. In the frame of the assessment of the structural integrity of such components in terms of fracture toughness and damage tolerance, the crack-resistance was studied employing fracture mechanics testing techniques, such as impact toughness (Charpy) and Crack-Tip-Opening-Displacement (CTOD) according to ISO 148-1 and BS 7448-1 standards respectively. The heat treated CW510L at 775 °C for 60 min exhibited an improvement of fracture toughness in terms of impact energy (from 47 J to 52 J) and critical CTOD (from 0.32 mm to 0.50 mm), while in case of CW511L heat treatment performed at 850 °C for 120 min caused a slight deterioration of fracture toughness in terms of impact energy (from 104 J to 84 J) and critical CTOD (from 0.71 mm to 0.54 mm). Moreover, fractographic analysis was comprehensively performed at the various transition fracture zones and the emergent failure mechanisms were identified and documented for both examined brass manufacturing conditions (“as received” and after “final heat treatment”). The compilation of fracture mechanics properties and the acquired fractographic information have resulted evidently in the formulation of salient interpretation and postulation of hypotheses concerning the influence of the dominant microstructure and loading regimes on crack propagation and the observed failure mechanisms.