An in-situ approach for fabricating network reinforced CoCrFeNi matrix composite

The CoCrFeNi HEAs offer immense promise for advanced engineering applications. However their strength at high temperatures needs much improvement. In an effort to strengthen the highly ductile matrix, here we report a CoCrFeNi composite in which a continuous network composed of TiN nanograins is placed around the FCC matrix. To accomplish this, initially a CoCrFeNi powder with an in-situ coating of TiN layers was fabricated. Afterwards, the sintering parameters for the designed powders were optimized. At higher sintering temperatures, liquid phase was introduced on the powder interfaces to achieve complete densification. Additionally, prolonged formation of the liquid phase lead to a robust particle-particle adhesion. The liquid infiltration at the interfaces directly influenced the strengthening and toughening of the composite. At optimal sintering conditions, the composite had a density, hardness and flexural strength of 7.49 g/cm3, 450 HV and of 1.78 GPa, respectively.