Effect of machined surface integrity on fatigue resistance of aluminum-silicon alloy ZL109

Abstract

In this paper, the fatigue resistance of aluminum-silicon (Al-Si) alloy specimens obtained by single-step feed forward cutting (PZ), step-by-step feed forward cutting (FZ) and step-by-step forward-reverse finish cutting (FZF) was investigated based on the characterization of surface integrity (roughness, residual stress, microhardness), using a combination of turning experiments, surface integrity analysis and fatigue performance analysis. The fatigue life of the specimens was tested at room temperature and high cycle under the three machining processes, and an empirical model of the fatigue life was established and analyzed for the fatigue fracture morphology. The results showed that the fatigue life of the specimens can be improved by changing the surface integrity such as increasing the microhardness, reducing the surface roughness, and increasing the surface residual compressive stress. Compared with PZ, the fatigue life of FZ and FZF samples increased by 61.8 % and 64.1 % respectively. And it is obtained by analyzing experimental result and fatigue fractures that the relatively poor surface topography (i.e., the larger surface roughness) could induce stress concentration and accelerate fatigue crack initiation, the compressive residual stress mainly inhibited the crack propagation process to improve fatigue strength, and the work hardening could restrain the initiation of fatigue cracks.