Akademik Veri Yönetim Sistemi
MATERIALS CHARACTERIZATION, cilt.196, ss.1-12, 2023 (SCI-Expanded)
In this study; turning, milling, heat treatment and shot peening (SP) post-process operations alone or in different
combinations were performed on Ti6Al4V specimens which were produced by selective laser melting (SLM); then
the effects of these operations on the fatigue life, residual stress, microstructure, microhardness and surface
roughness were investigated. SP processes were carried out in two different types, traditional and multiple, and it
was observed that the multiple SP process, which was carried out with the same almen intensity as traditional,
with a smaller ball diameter, was effective in reducing the surface roughness. As a result of the heat treatment, α
+ β transformation was observed in the microstructure. α phase was seen in both lamellar and globular forms.
Traditional SP and multiple SP processes provided a significant increase in microhardness values in the 0–250 μm
depth range. A significant decrease in the microhardness values of the heat-treated specimens was observed due
to the α + β transformation in the microstructure. Traditional SP and multiple SP processes enabled the residual
stress type to become compressive type in both the x-axis and the y-axis in the 0–150 μm depth which is a very
critical region for fatigue cracks despite the x-axis direction surface unmachined. Fatigue test were performed on
machined, multiple shot-peened and machined after heat-treated specimens. The best results in terms of fatigue
strength were obtained in the specimens that were heat-treated. It was observed that the most important cause of
fatigue crack initiation in multiple shot-peened specimens was an internal defect located deeper than 250 μm.
Fisheye formation was observed on fracture surfaces of some multiple shot-peened fatigue specimens.