Effect of Laser Energy on the Structure of Ni46–Ti50–Cu4 Shape-Memory Alloy

Abstract

The structural and physical properties of nickel–titanium–copper shape-memory alloy and the effect of laser irradiation on the alloy were investigated in this study. The alloy was prepared using the powder metallurgy method. Powders of 50% Ti, 46% Ni, and 4% Cu by weight were mixed and then cold-compacted at 600, 700, and 800 MPa to form cylindrical samples 11mm in diameter and 16.5 mm in length. The samples exhibited sufficient green strength for handling after compaction and were subsequently sintered at 850°C, 900°C, and 950°C for five hours in an electric vacuum tube furnace. The optimum compacting pressure and sintering temperature were identified using Minitab software. Samples prepared under the optimum process conditions were then irradiated using a pulsed ND: YAG laser at 300mJ, 400mJ, 500mJ, and 600mJ. The effects of the laser treatments were investigated through optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and microhardness testing. The results revealed that whereas laser irradiation at 500mJ enhanced the surface properties of the shape-memory alloy, laser irradiation at 650 mJ damaged the surface of the alloy.