High-temperature stability of Ni-3 wt.% SiCNP composite and the effect of milling time

The microstructural evolution and tensile properties of nickel-silicon carbide nano-particles (Ni-3wt.%SiCNP) composites with milling time ranged from 8 to 48 h have been examined. High temperature aged and reference samples were investigated to clarify their high temperature stability. The TEM characterizations showed that the coarsening of dispersed SiCNP occurred with increasing milling time, whereas their sizes kept stable under different aging temperatures. The EBSD results indicated that the mean grain size decreased and increased respectively with increasing milling time and aging temperature. Two different recrystallization mechanisms, boundary bowing out and subgrain growth, were assumed to be responsible for the grain growth. The tensile test results showed that both the yield and tensile strengths of reference and aged samples increased as a function of the milling time. As milling time extended, the total elongations gradually decreased in the case of reference samples, but slightly decreased firstly and then increased in the case of the aged ones. The relationship between the microstructural evolution and the variations of tensile properties has been discussed in this study.