Titanium and its alloys are comparatively recent newcomers to the metallurgical market. They are gaining widespread acceptance for use in the recreational, aerospace, biomedical, petro-chemical, and commercial processing industries due to their combination of unique and advantageous properties, including high strength, low density, and superior corrosion resistance to most aggressive agents. The material properties of titanium and its alloys can be optimized and tailored by engineering the microstructure via control of chemistry, processing route, and heat treatment. The morphology of the two crystallographic allotropic phases can be manipulated to refine the structure and produce desirable mechanical property combinations. Microstructural constitution of the titanium alloys is classified according to the dominant phase within the alloy; alpha + beta (α + β) titanium alloys are the most widely used alloys. The temperature of the final heat treatment of the α/β components is governed by the service requirements. In order to evaluate the behavior of these alloys for future applications, it is imperative that the microstructural features and characteristics be quantified and examined on a spatial dimension. The Robo-Met.3D is a high precision robotic serial sectioning device that can fulfill this need.
Initially, several months were spent resolving problems with the functioning of the Robo.Met.3D. Two-dimensional (2-D) stereology was done on Timetal 550 using automated batch processing with Adobe Photoshop and Fovea Pro. Images from different locations on the gage were obtained and compared. Final data demonstrated quantitative differences which were the result of the heat treatment. Discrepancies and inconsistencies in the data were identified as limiting factors in the reproducibility of the procedure in future work.
Serial sectioning using focused ion beam (FIB) was performed using Timetal 550, and three-dimensional (3-D) reconstruction was done using IMOD. Robo-Met.3D procedures and algorithms were identified for serial sectioning collection for titanium alloys using Ti-6Al-4V.
Recommendations for future work include developing more efficient procedures for coloring in the microstructural features in the Adobe Photoshop CS™. A new procedure is needed to mount and polish the sample to prevent sample curvature due to the polishing step. Also, the small size of the secondary alpha (α) presents a challenge when examining microstructural features; however, it is imperative that these features be examined in the future to determine their effect on mechanical properties.