Study of Microstructure, Mechanical Properties, and Corrosion Behavior of As-Cast Ni-Ti and Ti-6Al-4V Alloys

Abstract

Ni-Ti and Ti-6Al-4V alloys were cast as ingots using vacuum arc remelting furnace. The microstructure of as-cast Ni-Ti alloy consists of NiTi matrix as well as Ti2Ni dendrites. As-cast Ti-6Al-4V alloy revealed a structure composed of equiaxed β grains and varied α-phase morphologies. Ti-6Al-4V alloy registered maximum ultimate compressive strength of 2042 MPa, and also reported large reduction in height (18%). However, Ni-Ti alloy showed minimum ultimate compressive strength of 1804 MPa and low reduction in height (3%). The wear rate of both as-cast Ni-Ti and Ti-6Al-4V alloys significantly increased with saline solution (0.9% NaCl) condition compared to the dry testing condition. Saline solution harmed the wear resistance by about 2-4 times compared to the dry conditions. The corrosion rate of Ti-6Al-4V in saline solution (0.9% NaCl) was 0.000171 mm/yr which is almost half the value of Ni-Ti alloy (0.00038 mm/yr).