Effects of shot peening on the nanoindentation response of Cu47.5Zr47.5Al5 metallic glass

• Published in: Journal of alloys and compounds 2014-02, Vol.586, p.S36-S40
• Main Authors: Fornell, J., Concustell, A., Greer, A.L., Suriñach, S., Baró, M.D., Sort, J.
• Format: Article
• Language: English
• Subjects: Amorphous materials; Annealing; Friction; Hardness; Mechanical properties; Metallic glasses; Microstructure; Nanoindentation; Shot peening; Softening
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.12.051

• Shot peening induces an increase of relaxation enthalpy in Cu47.5Zr47.5Al5 glass. • The increase of free volume induces mechanical softening. • Numerical simulations show a decrease of cohesive stress and friction coefficient. • Annealing causes opposite effects as compared to shot peening. The effects of shot peening (SP) on the nanoindentation response of Cu47.5Zr47.5Al5 metallic glass, both in the as-cast state and after thermally induced structural relaxation (i.e., after annealing close to the glass transition), are investigated. As expected, annealing causes an increase of hardness attributable to annihilation of free volume. Conversely, nanoindentation tests, carried out on a transverse section at different distances from the SP surface, reveal that SP induces mechanical softening. Both the hardness and the reduced Young’s modulus progressively decrease as the peened surface is approached. Finite-element simulations of the nanoindentation curves indicate that the cohesive stress and the Mohr–Coulomb friction coefficient also decrease after SP, an observation which is in line with the induced mechanical softening. Differential scanning calorimetry measurements reveal an increase of the relaxation enthalpy, particularly when SP is performed on the previously annealed metallic glass, consistent with deformation-induced creation of free volume.