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1 Composites Theory and Practice

1 2021

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Experimental investigation and optimization of mechanical properties of nitinol reinforced composites

Kalepu Sambasivarao, Nallu Ramanaiah

Composites Theory and Practice

2021

R. 21, nr 4

154--160

Metal matrix composites (MMCs) have elevated properties when compared to their parent metals. Aluminium, due to its light weight has a versatile set of applications. In the present work, the 2024 aluminium alloy was chosen as the metal matrix, was melted and stir cast at a temperature of around 900°C along with an addition of a nickel-titanium (Ni-Ti) in powder form as the reinforcement in varying proportions (2, 4, 6, 8% weight fractions). Tests were conducted to analyse the tensile strength, impact strength, elongation and microstructure of the produced specimens. SEM micrographs revealed that the MMCs with 2 and 4 wt.% reinforcement exhibited better dispersion of the reinforcement. The composites having the 4 and 6 wt.% additions of Ni-Ti powder exhibited better ultimate tensile strength when compared to the other specimens, whereas the one with the 8 wt.% addition of Ni-Ti powder revealed better impact strength. Some agglomerations of the Ni-Ti particles were observed on the fractured surface. When evaluating the optimum result using design expert or the design of experiments, it is understood that when the data points are evenly split, either transformation or a higher order model can improve the fit to obtain the optimum result. The yield strength of the metal matrix composite which indicates the ability of the material to withstand permanent deformation varies with respect to the additions of Ni-Ti powder. It occurred that the MMCs with the 4 and 6 wt.% reinforcement produced better results when compared with the 2 and 8 wt.% ones, respectively. The impact strength of the composite containing the 8 wt.% addition exhibited better resistance when compared with the 2, 4 and 6 wt.% reinforced MMCs. It was revealed that the 8 wt.% addition of Ni-Ti powder to the metal matrix resisted fracture due to the applied load. The lower limit for the ultimate tensile strength is 186 MPa and for the upper limit it is 212.14 MPa, which are within the acceptable range; therefore, the optimum results are within the limits.