Bilgilendirme: Sürüm Güncellemesi ve versiyon yükseltmesi nedeniyle, geçici süreyle zaman zaman kesintiler yaşanabilir ve veri içeriğinde değişkenlikler gözlemlenebilir. Göstereceğiniz anlayış için teşekkür ederiz.

Malzeme Bilimi ve Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/396

Browse

Browsing Malzeme Bilimi ve Mühendisliği Bölümü Yayın Koleksiyonu by Author "Bilgin, Guney Mert"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Article
    Citation - WoS: 35
    Citation - Scopus: 37
    Effect of Post Fabrication Aging Treatment on the Microstructure, Crystallographic Texture and Elevated Temperature Mechanical Properties of In718 Alloy Fabricated by Selective Laser Melting
    (Elsevier Science Sa, 2022) Bilgin, Guney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F.; Ozer, Seren; 52373
    The effect of building direction and post fabrication aging treatment on the microstructure, crystallographic texture and high temperature mechanical properties of Inconel 718 (IN718) alloy fabricated by selective laser melting (SLM) method was investigated. After aging, arc-shaped structures seen in as-fabricated samples dis-appeared and converted into a mixture of columnar and equiaxed grains. Nano-sized gamma '' and/or gamma' precipitates were formed upon aging; however, MC type carbides and Laves phase encountered in as-fabricated samples were not dissolved completely after aging. Moreover, aging did not alter the texture ((001)//building direction (BD)) of as-fabricated samples. Mechanical properties of the alloys under tension were influenced by the build direction, aging time and test temperature. As-fabricated samples produced in vertical direction exhibited higher room temperature strengths with lower ductility due to orientation of overlapped prior melt pools. Room temperature tensile test results revealed that peak aging caused a significant improvement in ultimate tensile strength (UTS), from 1066.5 MPa and 998.4 MPa to 1408.5 MPa and 1330.4 MPa whereas elongation values decreased from 27.5% and 32.2% to 19.6% and 23.7% in vertically and horizontally built samples, respectively. Peak-aged samples (aged at 700 degrees C for 8 h) tested at 600 degrees C displayed serrated regions in their stress-strain curves due to dynamic strain aging (DSA). Although strength values of the samples displayed an expected decrease by temperature, ductility of the samples reduced to minimum at temperatures around 700-800 degrees C, which was attributed to intermediate temperature embrittlement.
  • Thumbnail Image
    Article
    Citation - WoS: 32
    Citation - Scopus: 36
    Optimization of the Mechanical Properties of Ti-6al Alloy Fabricated by Selective Laser Melting Using Thermohydrogen Processes
    (Elsevier Science Sa, 2017) Esen, Ziya; Akin, Seniz Kushan; Dericioglu, Arcan F.; Bilgin, Guney Mert; 52373
    2-step Thermo Hydrogen Process (THP) including hydrogenation and dehydrogenation steps was applied to Ti-6Al-4V alloy fabricated by selective laser melting (SLM) process to refine the microstructure and to increase the ductility of the alloy. It was observed that as-fabricated alloy's surface was composed of oxides of titanium and aluminum, which may alter the hydrogenation kinetics. The hydrogen treatment for 1 hat 650 degrees C, the maximum hydrogen solubility temperature of the alloy, transformed starting non-equilibrium alpha'-martensitic phase to 13 and 8 (TiH2) phases. On the other hand, very fine discontinuous beta-phase was formed along with alpha-phase as a result of dehydrogenation at 700 degrees C for 18 h, which decreased the hydrogen level well below the starting value and caused transformation of delta-phase to fine alpha-phase. In contrast to commonly used THP treatments consisting of betatizing at high temperature, 2-step treatment prevented grain boundary alpha-phase formation as well as excessive grain growth. About 110% and 240% increments were detected in % Elongation (EL) and % Reduction in Area (RA) values, respectively, as a result of 2-step THP, while the strength decrease was limited to 10%. The change in ductility of the alloy was also verified by transformation of flat and shiny fracture surfaces seen in SLM fabricated alloy to a fracture surface containing equiaxed dimples after THP treatment. The hardness drop in the alloy after hydrogenation and dehydrogenation treatments was attributed to relief of residual stress and formation of equilibrium alpha and beta-phases.