Depth-sensing indentation study of superconducting MgB2 wire

Superconducting MgB2 composite wire was prepared by packing blended MgB2 inside of Cu tubes using the powder-in-tube (PIT) method. Mechanical properties of the sample were then characterized by using a dynamic ultra-micro indentation experimental technique. The hardness (H) and the elastic modulus (E) values were calculated by the method of Oliver and Pharr. It was found that both the hardness and the elastic modulus exhibit significant peak load dependence (i.e., indentation size effect (ISE)). The experimental hf / hmax values, lower than the critical value (0.875), indicate that the MgB2 wire shows work hardening behaviour.