How We Learned to Love the Phase Diagram with a Ti-Cr Alloy Characterization Lab

While many students learn how to read and use a phase diagram in introductory materials courses, greater appreciation for such a tool can be garnered through the laboratory setting. A laboratory module for a “Structures of Materials” class (a “core class” for materials majors) has been developed to demonstrate the usefulness of phase diagrams, as well as, to emphasize the connections among processing, structure, and properties. Competence in determining stable phases, phase compositions, and mass fractions of phases are not the end goal, per se, but transpire since the skills are required to help solve a puzzle. Students are given a set of Ti-Cr alloys (different compositions that have also been processed at different temperatures), however all the samples are unmarked. Given a few clues, the students must then investigate the samples through x-ray diffraction, metallography, and hardness tests to sort out and identify the samples. The lab module is open-ended in approach, and different groups arrive at the same solution in different ways. Several experimental techniques and different concepts (e.g., lattice constants, Vegard’s rule, strengthening mechanisms) are brought together in a cohesive manner. Students have found the lab module to be quite challenging, yet in the end, also very satisfying.