Nanoindentation study on the mechanical behaviour of 3-D printed high-entropy alloys

• Main Author: Lum, Natalie Chee Shuan
• Other Authors: Upadrasta Ramamurty
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150967
• Institution: Nanyang Technological University

High entropy alloys (HEAs) have recently been an attractive research field for achieving excellent properties that conventional alloys do not possess. Due to their excellent functional and mechanical properties, multi-component HEAs have the potential for a wide range of industrial applications. However, the features that HEAs offer make it difficult to fabricate, limiting the selection of manufacturing techniques. Additive manufacturing (AM) has the capability to overcome this issue with its numerous features and qualities. Selective laser melting (SLM) was employed to fabricate the Al0.5CoCrFeNi HEA samples with two different sets of processing parameters, producing high and low porosity samples. This report investigates the microstructure of the Al0.5CoCrFeNi HEA samples fabricated by SLM and establish the microstructure-property relations. The microstructure of the HEA samples was examined using scanning electron microscopy (SEM) as well as x-ray diffraction (XRD). It was found that the SLM samples composed of face centred cubic phases (FCC) accompanied with body centre cubic phases BCC and ordered body centred cubic phases (B2) which are different from the conventional casting with disordered body centred phases A2 and FCC phase. The hardness property of the HEA samples was also studied. The low porosity sample had a higher hardness of ~310 HV while the high porosity sample with ~298 HV. Through a comparison of the samples, it can be concluded that the low porosity sample has a better hardness than the high porosity sample which attributes to a higher fraction of BCC/B2 phase present in the low porosity sample.