Designing of Ti-Mg composites for various applications

Bütev Öcal, Ezgi
In this study, galvanic corrosion of Ti-Mg based composites has been examined by combining different Mg-alloys with Ti6Al4V alloy and by addition of Na-rich layer between two dissimilar metals. After determining the wetting behavior of liquid unalloyed Mg, AZ91, and WE43 alloys on solid Ti6Al4V alloy, three different composites were manufactured via infiltration of liquid Mg/Mg-alloys into porous Ti6Al4V alloy skeletons. The same procedure was also repeated after coating the porous surfaces of Ti6Al4V alloy by alkali treatment. Electrochemical and non-electrochemical tests have been conducted in simulated body fluid (SBF) separately for bulk samples of Mg/Mg alloys, and their composite counterparts with and without Na-rich coating to reveal and compare corrosion mechanisms. The composites containing unalloyed Mg and AZ91 alloy exhibited greater relative density due to their better wettability on Ti6Al4V alloy. Bulk Mg/Mg alloys displayed micro galvanic corrosion, and AZ91 had the highest corrosion resistance with its homogenously distributed Mg17Al12 intermetallics. On the other hand, the coupling of Mg/Mg-alloys with Ti-alloy intensified the galvanic corrosion; however, the corrosion was not as severe as Ti6Al4V-Mg composites when AZ91 and WE43 alloys are used. In addition, formation of TiAl3 phase in the Ti6Al4V-AZ91 composite reduced the galvanic effect significantly. The presence of Na-rich coating in the composites alleviated the galvanic effect. Although its impact was not visible in composites containing Mg-alloys, remarkable improvement in corrosion resistance was obtained in Ti6Al4V-Mg composite. Na-rich coatings not only reduced the galvanic corrosion but also enhanced the bioactivity of composites by allowing precipitation of Ca-P phases.
Citation Formats
E. Bütev Öcal, “Designing of Ti-Mg composites for various applications,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Metallurgical and Materials Engineering., Middle East Technical University, 2019.