Fatigue crack growth of SLM Ti-4Al-6V processed by ultrasonic impact treatment

Abstract

The paper presents the investigation results of fatigue behavior of three types of materials: (i) wrought Ti-6Al-4V, (ii) Ti-6Al-4V fabricated using selective laser melting and (iii) Ti-6Al-4V fabricated using selective laser melting (SLM) with subsequent post-build processing by Ultrasonic Impact Treatment (UIT). The deformation behavior and fracture pattern of the specimens under cyclic loading was studied by means of scanning electron microscopy of the fracture surfaces and digital image correlation (DIC). The results obtained show that the proposed technique for post-build treatment of SLM specimen increases their fatigue durability by ∼60%. Moreover, the latter tends to exceed the lifetime of wrought Ti-6Al-4V. SEM and DIC studies witness the increase in ductility of the post-build treated material, which is supported by more ductile fracture surface pattern and larger strain of the specimen during cyclic loading.