Microstructures and Mechanical Properties of Alcocrfeni2.1/6061-T6 Aluminum-Matrix Composites Prepared by Friction Stir Processing

Abstract

6061-T6 aluminum matrix composites reinforced by AlCoCrFeNi2.1 high-entropy alloy (HEA) were obtained using friction stir processing (FSP), and the resultant composites were further strengthened by T6 heat treatment. The effects of reinforcement phase content on the microstructure and mechanical properties of composites were investigated. The results showed that the HEA particles were homogeneously distributed in the composites under the effect of multi-pass reciprocating friction stir processing. The particle-stimulated nucleation mechanism decreased the composite grain size with the increase in the volume fraction of HEA. Because of the negative mixing enthalpy between the Si element and the Co, Cr, Fe, Ni elements involved in HEA, Si segregation occurred in the interface region. It was speculated that no intermetallic compound formed in the interfacial zone. Compared with friction stir processed-6061, the hardness and tensile strength of the composites with 15% HEA reached 72 HV and 222.9 MPa and increased by 28.6% and 25.6%, respectively. After T6 aging heat treatment, the hardness and the tensile strength reached 125 HV and 332.1 MPa, further improved by 73.6% and 49.0%, respectively.

Keywords: High-entropy alloy particle, aluminum-matrix composites, Friction Stir Processing, Microstructure, Mechanical properties