Synthesis and Characterization of TiB₂-Reinforced AlCoCrFeNi_2.1 High-Entropy-Alloy Matrix Composite

Abstract

Advanced manufacturing technologies have imposed higher demands on the strength, hardness, and high-temperature stability of materials, such as cutting tools, molds, and wear-resistant parts. Metal matrix composites with excellent comprehensive properties are expected to meet these demands. High-entropy alloys (HEAs), composed of unique multi-principle elements, offer high strength, hardness, and excellent high-temperature stability, superior to traditional cemented carbides in some cases. Here, the AlCoCrFeNi2.1 HEA reinforced by TiB2 was fabricated by an innovative alliance of mechanical alloying (MA) and spark plasma sintering (SPS). It was found that tuning the milling time and content of the reinforced phase could effectively realize the uniform distribution of the TiB2 reinforcement phase in the matrix. The AlCoCrFeNi2.1 with 5 vol.%TiB2 after MA for 2 h resulted in the particle refinement of TiB2 and the uniform distribution of TiB2 in the matrix. And the bulk sintered at 1150 °C exhibited an excellent combination of a compressive yield strength of 1510 MPa, a compressive strength of 2500 MPa, and a high hardness of 780 HV. The analysis of different strengthening mechanisms suggests that the fine grain strengthening and precipitation strengthening make the HEA composite possess excellent compressive yield strength and fracture strength.

Keywords

• high-entropy alloy
• mechanical alloying
• spark plasma sintering
• reinforcement particles