Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
2 results
Search Results
Item Laser surface melting of Mg-Zn-Dy alloy for better wettability and corrosion resistance for biodegradable implant applications(Elsevier B.V., 2019) K.r, R.; Bontha, S.; M.r, R.; Das, M.; Balla, V.K.In order to improve the performance of magnesium (Mg) for resorbable implant applications, Mg-1Zn-2Dy alloy was developed and the surface of the alloy has been modified by melting using lasers. Laser melted samples, at different laser energy density, were then subjected to microstructural, hardness, wettability and in-vitro degradation assessment. The microstructure of the Mg-Zn-Dy alloy mainly consisted of ?-Mg and eutectic phase (Mg 8 ZnDy). The melted region of the alloy surface evolved with fine grain microstructure at the near surface region and columnar grains near to the liquid solid substrate. The degree of grain size refinement obtained at the melted zone in the order of 1–2 ?m. The cross sectional microhardness of the modified zone was measured by Vickers microhardness tester. Due to these microstructural refinements and solid solution strengthening the surface hardness of laser treated alloy increased by two-fold. It was found that as the energy density increased the surface roughness along with the surface energy also increased. The wetting behaviour of the surface was estimated through measuring the contact angle by dropping the polar and non-polar liquid. Results showed that the surface energy is also found to change with LSM due to changes in the surface morphology, microstructure and chemical composition of the material. The detailed degradation study was carried out by immersing the samples in hanks balances salt solution (HBSS).The improvement in the degradation behaviour followed by laser surface melting is related to the microstructural refinement as a result of rapid heating and cooling of the melted zone. © 2019 Elsevier B.V.Item Tailoring surface characteristics of bioabsorbable Mg-Zn-Dy alloy using friction stir processing for improved wettability and degradation behavior(Elsevier Editora Ltda, 2021) Rokkala, U.; Bontha, S.; Ramesh, M.R.; Balla, V.K.; Srinivasan, A.; Kailas, S.V.Magnesium (Mg) and its alloys are currently under consideration for use as temporary implants. However, early degradation and maintaining mechanical integrity is a significant concern. Surface modification techniques are used to improve mechanical and corrosion properties of Mg based alloys. In the present study, friction stir processing (FSP) was used to tailor the surface characteristics of Mg-1Zn-2Dy (wt.%) alloy for temporary implant applications. The FSPed alloy was characterized using EBSD to understand the influence of FSP on crystallographic texture, grain size and grain boundaries and thereby their effect on corrosion, wettability and hardness. Results showed that the grain size of stir zone (SZ) was refined to less than 3 ?m, as a result of dynamic recrystallization (DRX) during FSP and the FSPed alloy exhibited better wettability than as-cast alloy. An increase in the hardness (11.7%) and elastic modulus (6.84%) of FSPed alloy were also observed. Electrochemical corrosion and weight loss methods were conducted in Dulbecco's Modified Eagle's Medium (DMEM) with, 10% Fetal Bovine Serum (FBS) physiological solution. The lower degradation rate (0.72 mm/yr) of FSPed alloy has been attributed to the fine grains and evenly distributed secondary phase particles. Further, the influence of grain boundary characteristics and crystallographic texture on the corrosion behavior have been investigated. © 2021 The Author(s).