College - Author 1
College of Engineering
Department - Author 1
Materials Engineering Department
Degree Name - Author 1
BS in Materials Engineering
College - Author 2
College of Engineering
Department - Author 2
Materials Engineering Department
Degree - Author 2
BS in Materials Engineering
College - Author 3
College of Engineering
Department - Author 3
Materials Engineering Department
Degree - Author 3
BS in Materials Engineering
Date
6-2023
Primary Advisor
Blair London, College of Engineering, Materials Engineering Department
Abstract/Summary
An investigation into the growth kinetics of alpha case in Ti-6Al-4V in the presence of oxygen was conducted for different forging thermal cycles. This was done to determine whether the alpha case should be removed after each thermal cycle or as the final step after forging. The thermal cycles consisted of four hours at 1750 °F. Samples were subjected to this treatment one, two, three, and four times along with a continuous sixteen hour hold. Four cycle and Hold samples were subjected to an additional thermal cycle above the beta transus at 1925 °F. These then went through a final stress relieve cycle at 1350 °F for four hours. The alpha case depth was measured for each of these samples using three methods. These include area fraction analysis using ImageJ, visual estimations, and Vickers microhardness testing. Each of these three methods showed a large initial case growth followed by diminishing growth rates. Area fraction was the most conservative measurement resulting in significantly higher values for depth than the other two methods. Visual estimations and Vickers hardness corroborated each other’s values. After one four hour thermal cycle at 1750 °F the case depth by visual estimation is 250 micrometers. The second, third, and fourth thermal cycles are 366, 388, 392 micrometers respectively. After four thermal cycles at 1750 °F, samples were heated to 1925 °F for half an hour resulting in a decrease in case depth to 292 micrometers, and a subsequent heat treatment at 1350 °F for four hours resulting in a depth of 263 micrometers. The sixteen hour hold samples undergo the same 1925 °F and 1350 °F cycles with similar results. The Hold has a depth of 537 micrometers, which first decreased to 318 and then to 281 micrometers.
URL: https://digitalcommons.calpoly.edu/matesp/272