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Session 2464

How we learned to love the phase diagram with a Ti-Cr alloy characterization lab

Katherine C. Chen Materials Engineering Department California Polytechnic State University, San Luis Obispo, CA 93407

Abstract

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.

Introduction

“Structures of Materials” is the first core class in the Materials Engineering curriculum at Cal Poly, where students delve into much more detail about crystal structures, symmetry, defects, and microstructures. These same topics are introduced in an earlier “Introduction to Materials Engineering” course that also serves as a survey course to all other engineers. Students often have varying degrees of understanding and appreciation for phase diagrams. While sometimes students can work out problems dealing with phase diagrams (e.g., mass fractions), they do not always fully understanding the concepts. This particular laboratory enables students to appreciate the utility of phase diagrams by posing questions within a context that ties together processing, structure and properties of alloys. Students typically demonstrate frustration at the beginning of the lab, but then consistently rate this lab as the most valuable learning experience of the course on surveys.

“Proceedings of the 2003 American Society for Engineering Education Annual Conference & Exposition Copyright © 2002, American Society for Engineering Education”

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Chen, K. (2003, June), How We Learned To Love The Phase Diagram With A Ti Cr Alloy Characterization Lab Paper presented at 2003 Annual Conference, Nashville, Tennessee. 10.18260/1-2--12378