Gum metal is a class of Ti-Nb based alloys first developed by Toyota in the early 2000s. These alloys display anomalous behavior over a range of properties, with many of these oddities emerging only after severe plastic deformation (SPD) has been incurred on the material. Examples of this include a highly nonlinear elastic regime, high ductility, an absence of work hardening, high elastic limit, low thermal expansion coefficient and Young’s modulus over a wide temperature range, as well as a high yield strength (over 1 GPa). These many novel properties give gum metal potential applications ranging from sporting goods (tennis rackets, golf clubs, and fishing line) to biomaterials and instrumentation meant in extreme environments.
While many attempts have been made to explain the basis for gum metal’s unique properties, questions still remain regarding the origin of many of its properties. We are currently attempting to gain a great theoretical understanding of the effect of severe plastic deformation on the thermal expansion of gum metal, the nonlinear nature of its elastic regime, and possible deformation mechanisms that can allow for such a high yield strength.
In addition, we are attempting to design materials with gum metal like properties by taking advantage of the fact that gum metal was designed by tuning the material to be near an elastic instability. Our investigations involved developing elastic indicators for gum metal behavior and screening in magnesium alloys as well as the Materials Project’s elastic constants database of ordered structures.