In this Academia (Milwaukee School of Engineering University and Rockford IL High school) collaboration with Industry and an International Research Center, the functionally graded Ti-6Al-4V + Mo samples are analyzed to study the effect of the addition of Molybdenum on material properties. Ti-6Al-4V is a common alloy used for aerospace and/or biomedical applications due to its high strength and low density. Molybdenum has been employed to increase the biocompatibility of Ti-6Al-4V. Deposited on a pure Ti-6Al-4V substrate were two samples of Ti-6Al-4V with layers of differing percentages of Mo, produced at a scanning speed of 0.3 m/min (0.005 m/s) at the National Laser Center of the Council of Scientific and Industrial Research, Pretoria, South Africa. The samples were produced with 6 tracks in each layer with 50% overlap, giving each sample a total width of 12 mm. One sample was manufactured with layers containing 15-10-5-0-5-10-15 wt% Mo at 1500 W laser power. Another sample was prepared with 0-5-10-15-10-5-0 wt% Mo at 1700 W. The samples were subsequently characterized at Innio’s Materials Laboratory, Waukesha, Wisconsin, USA. The LECO AMH 55 microhardness testing system and JEOL JSM IT300LV scanning electron microscope were employed for determining the hardness and microstructure of the two samples.The microstructures of 0% Mo showed Widmanstätten alpha (long, columnar grains) which is expected in Ti-6Al-4V. With percent Mo increasing, such layers indicated lamellar microstructure, with Mo being a ß stabilizer. In some instances, hardness increased which indicated martensitic structure perhaps caused by fast cooling. Also, the properties of lower and upper layers of the same concentration of Mo were not similar due to differing heat treatment occurring in the process of printing and intermetallic bonding. &nbsp;The cooling rates within each layer may have been different depending on where it is in the sample, and how many layers were deposited on top of it. These different cooling rates may have led to different mechanical properties within layers of the same composition. This paper is thus aimed at discussing underlying factors for the results obtained on graded samples at different laser powers (1500 and 1700 W) in detail. It is inferred from the findings that the higher percent of Mo (above 10%) is not advisable for biomedical applications due to cracking and other related issues. The results indicate need for further research to optimize the laser metal deposition process so as to yield consistent production of functionally graded materials.&nbsp;.&nbsp;

Laser Metal Deposition of Functionally Graded Ti-6Al-4V + Mo Samples and Characterization Studies Metal Deposition of Functionally Graded Ti-6Al-4V + Mo Samples and Mo Samples and Characterization Studies

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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