Effect of Nickel Addition on Microstructure and Mechanical Properties of the Spark Plasma Sintered Ti–6Al–4V Alloy

The effect of nickel addition (2–6 wt%) to Ti–6Al–4V has been investigated using spark plasma sintering. The sintered samples were studied and characterized by using field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Mechanical properties of the sintered samples were determined. Results show that an increase in nickel addition significantly reduces the relative densities from 97.9 to 95.9% and the microhardness of the alloys increases from 330 to 502 HV₅₀₀. The microstructural studies reveal a transformation; as Ni content increases, the equiaxed alpha phase and Widmanstatten alpha platelets in the Ti–6Al–4V alloy get refined and develop the clear grain boundaries with Widmanstatten lamellar microstructure. Sintered samples held for 30 min has the highest hardness value, while fracture morphology of the sintered compacts shows a transgranular fracture with fine dimple’s features, confirming good strength and cohesion of the grains. The percentage of elongation is greatly affected by the addition of nickel so that the sample exhibits a brittle nature with high ultimate tensile strength.