Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2022
Thesis Language: Turkish
Student: Akın DAĞKOLU
Supervisor: Oğuzhan Yılmaz
Abstract:
The use of the additive manufacturing processes in industrial, medical and aerospace applications is increasing with the increasing number of academic studies in this field. Advantages such as weight reduction with topology optimization and complex part designs, agile and low-cost manufacturing with decentralized on-site production, the ability to design parts to have multiple functions, and the possibility of repairing damaged parts has made the use of additive manufacturing in aerospace applications inevitable. In this thesis work, the characterization of the thermal residual stresses and their relationship with the material metallurgy of the L-PBF manufactured Ti-6Al-4V alloy were investigated. Residual stresses related to build direction were measured by hole drilling and XRD methods and the effects of solidification phenomenon on residual stress formation were explained. The internal structure of the material was examined by optical microstructure measurements and XRD phase analysis, and a correlation was made with the formation of residual stresses. It was found that the internal structure of the material consists of 98.7% α' phase and 1.3% prior β phase. It was observed that the grains were in a columnar structure and were oriented parallel to the build direction. The effect of stress relieving heat treatment on the internal structure of the material was found to be the biaxial growth of the measured microstructure elements and the thickening of the acicular structures. The residual stresses, parallel to the build direction (143 MPa, 1155 MPa) were measured 2-3 times of the residual stresses, perpendicular to the build direction (77 MPa, 424 MPa) with both methods used.
Key Words : Additive manufacturing, Ti6Al4V, residual stress,