Fig. 2

a Representative force-indentation depth curves of SS, Ni-Ti, and TMA wires. The left peak shifting denotes increase in hardness. The steeper the unloading curve the higher the indentation modulus (E _IT). The Ni-Ti unloading curve changes to a smaller angle slope as the load returns to 0, indicating a noticeable elastic material recovery. b Representative Vickers indent of SS and TMA wires, without a noticeable elastic recovery. c Vickers indentation of a Ni-Ti wire with curved sides (the direction of elastic recovery is pointed by the arrows) indicating extensive elastic recovery of the alloy around the tip