BS in Materials Engineering
Materials Engineering Department
Some Ti-6Al-4V forgings require a specific amount of α phase known as primary α in the finished product. The percentage of primary α is dependent on how close to the beta transus temperature forging is conducted. The beta transus temperature is affected by certain alloying elements. Carbon is one of the elements known to increase the beta transus temperature. Since each Ti-6Al-4V ingot contains varying amounts of carbon, testing on a variety of chemistries needs to be conducted. Cubes approximately 0.5 inches from low, medium, and high carbon chemistries were heat treated at temperatures below the beta transus in 18oF increments. Point counting was performed on metallographically prepared microstructures of each chemistry to find carbon’s effect on primary α percentage. The low and medium carbon samples showed linear trends with slopes of -0.249% α/T and -0.276% α/T respectively, and R2 values of 0.97 for both. The high carbon sample did not show the same linearity with an R2=0.91 for a linear regression, but had a slope of -0.392%α/T. Both the medium and high carbon compositions appeared to be shifted lower 5-10% primary α percentage.