Effect of Ti and Cu addition on microstructure, mechanical property and strengthening mechanism of nanocrystalline FeCrV-based MCAs

Nanocrystalline and nano-precipitation are two effective factors to improve comprehensive mechanical properties and irradiation tolerance. Motivated by creating the two important structural features, multi-component alloys (MCAs) FeCrVTix (x = 0.07,0.2,0.3,0.4) and FeCrVCuy (y = 0, 0.05, 0.08, 0.2, 0.3) were designed and fabricated by mechanical alloying and spark plasma sintering. The results showed that FeCrVTix was mainly composed of BCC matrix phase and tens of nanometers of Ti(C,N) precipitation, while BCC solid solution with nanoscale Cu precipitates was primarily present in Cu-containing MCA. Nanocrystalline is the prominent characteristic of the two MCAs, in which the average grain size is about 193 nm and 360 nm for FeCrVTi0.2 and FeCrVCu0.05, respectively. The coexistence of FCC Cu precipitates with about 13 nm and ultrafine BCC Cu of only ∼3 nm was observed within the gains of FeCrVCu0.05. The relationship between Cu nanoparticles and BCC matrix was determined. FeCrVTi0.2 and FeCrVCu0.05 demonstrate excellent mechanical properties with compressive yield strength of more than 1.90 Gpa, ultimate strength of above 3.0 GPa, plasticity of over 32 % and more than 590 HV microhardness at room temperature. The strengthening effects were qualitatively analyzed in detail to reveal the different influences of Ti and Cu addition on microstructure and the strengthening.