Effect of Mo addition on nanoindentation creep behavior of FeCoBSiNb bulk metallic glasses

Abstract

Novel Fe52Co20-xB20Si4Nb4Mox (x = 0–5) bulk metallic glasses with a diameter of 2 mm are successfully prepared by vacuum suction casting and the effect of Mo addition on their nanoindentation creep behavior is studied. Through a differential scanning calorimetry and creep compliance spectral analysis, it is found that the addition of a small amount of Mo increases the enthalpies (ΔH) and free volumes of the alloys. These factors stimulate the rearrangement of the atomic structures of the alloys and induce the adjustment of their internal structure, resulting in a relatively loose atomic packing state that allows the alloys to provide a continuous response to stress during creep deformation. By analyzing the unloading and load holding sections on the load-displacement curves, it is shown that the hysteresis of deformation induces the displacement jump phenomenon and the amplitude of the jump is inversely proportional to the equivalent stress. The larger the equivalent stress, the less obvious the displacement pop-out phenomenon. The changes in strain rate sensitivity exponent (m) and hardness are also studied. Combined with a delay spectral analysis, it is found that a 5% Mo addition significantly improves the creep resistance of the alloys.