A structural design approach toward metallic glass with simultaneous tunable thermal expansion and high structural stiffness

Although metallic glasses (MGs) possess relatively low thermal expansion coefficient (α) compared to their crystalline counterparts due to the existence of free volume, their α-values are still too large to meet the demands of practical application. Here, we report that a bi-material structure (BMS) consisting of curved traditional materials (e.g., Al alloy) with MGs can be used to obtain tunable α while maintaining high structural stiffness. The curved Al alloy has a pulling effect on the MGs when the curvature changes, limiting the thermal expansion of MGs. Through the theoretical model and finite element method analysis, it is further found that both α and stiffness can be significantly altered through changing the degree of curvature, the contact surface, and the thickness ratio of MG over Al alloy. The present study not only offers a solution to the α reduction of MGs but also suggests that BMS can be used to design advanced structural materials that possess adjustable α and high stiffness.