Microstructural Refinement of Ti-6Al-4V Alloy Fabricated by Additive Manufacturing Using Thermochemical Processes

2016-11-25
Bilgin, Guney Mert
Esen, Ziya
Kuşhan Akın, Şeniz Reyhan
Dericioğlu, Arcan Fehmi
Selective laser melting (SLM) is an additive manufacturing (AM) technology which enables the rapid fabrication of complex shaped parts directly from computer aided design (CAD) model providing reduction in process time, scrap and cost without the need of expensive tools. Ti-6Al-4V is the most widely used alloy in biomedical industry due to its unique example of biocompatibility along with its great corrosion resistance and superior specific strength with respect to other metals. Recently, because of attractive properties of Ti6Al-4V alloy, additive manufacturing industry is focused on manufacturing fully dense components with changing process parameters such as scanning speed, laser power and scanning pattern. However, highly localized heat inputs during very short interaction times and large thermal gradients give rise to some problems such as segregation and the development of non-equilibrium Į’ phase. The deficiency in achieving homogenously distributed microstructure consisting of Į + ȕ grains along with the presence of fine, acicular Į’ martensite grains after the AM of Ti-6Al-4V is undesirable. Therefore, post-processes like hot isostatic pressing (HIP) are required to follow AM to eliminate nonequilibrium phases and to enhance the ductility. In this study, alternatively a thermochemical process (TCP) involving the introduction of hydrogen into SLM fabricated Ti-6Al-4V alloy was investigated. The alternative post-processing includes following treatments; hydrogenation, ȕ solutionizing, eutectoid decomposition and elevated temperature vacuum dehydrogenation. It was found that after all thermohydrogen processes a very fine and equiaxed Į + ȕ microstructure without the presence of any residual hydrogen was obtained. Consequently, acicular Į’ martensite grain containing microstructure resulting from AM was transformed into fine Į+ȕ microstructure.
18th International Metallurgy & Materials Congress, İstanbul, Türkiye, (29 Eylül - 01 Ekim 2016)

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Citation Formats
G. M. Bilgin, Z. Esen, Ş. R. Kuşhan Akın, and A. F. Dericioğlu, “Microstructural Refinement of Ti-6Al-4V Alloy Fabricated by Additive Manufacturing Using Thermochemical Processes,” presented at the 18th International Metallurgy & Materials Congress, İstanbul, Türkiye, (29 Eylül - 01 Ekim 2016), İstanbul, Türkiye, 2016, Accessed: 00, 2021. [Online]. Available: http://www1.metalurji.org.tr/immc2016/IMMC2016_Bildiriler.pdf.