Effect of FeNb on microstructure and mechanical properties of Al-Cu-Ni alloy

Abstract

The present research work deals with the investigation of mechanical properties and microstructure evaluation by particulate reinforcement of ferroniobium (FeNb) into Al-5Cu-2Ni alloy. The two-step stir casting method was employed for the fabrication of the material. The metallography study was carried out with optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). The XRD peaks revealed the presence of the Fe2Nb phase and intermetallic compound phases of Al2Cu and Al3Ni2. However, the Fe2Nb phase is in the form of short sticks uniformly distributed around the intermetallic compound phases. Tensile strength, microhardness and impact strength were evaluated according to ASTM standards. The average tensile strength and Vickers microhardness of the Al-5Cu-2Ni matrix alloy were 179 MPa and 115 HV respectively. By adding 1%, 3% and 5% of FeNb particulate reinforcement into Al-5Cu-2Ni alloy, the tensile strength could be enhanced to 185, 193 and 207 MPa respectively. The corresponding microhardness values were 130, 132 and 151 HV, respectively. Thus, the addition of 5% ferroniobium particulate reinforcement material could significantly enhance the tensile strength and microhardness of the composites. Fractography revealed that fracture mode changes from ductile to brittle with the reinforcement of FeNb particles. The FeNb particles resist the dislocation movement of the intermetallic compound phases in the composites leading to micro-cracks and subsequent brittle fracture.