Decoupling of indentation modulus and hardness in silicate glasses: Evidence of a shear- to densification-dominated transition

•We use micro indentation plus thermal annealing to link the favored inelastic deformation mechanisms to glass composition.•The increase in densified volume comes at the expense shear flow.•Reduction of volume deformed by shear flow is confirmed by a reduction in ductility measured by M/H and pile-up.•When dissipating inelastic energy, a more open structure favors densification and a denser structure favors shear flow, which is a volume conservation process.•The non-monotonic evolution of hardness was linked to the composition through favored inelastic dissipation mechanisms.