Correlation between microstructure and deformation mechanism in Ti66Nb13Cu8Ni6.8Al6.2 composites at ambient and elevated temperatures
Materials Science and Engineering: A
School of Engineering
Funding information available at: https://doi.org/10.1016/j.msea.2019.138448
In this study, Ti66Nb13Cu8Ni6.8Al6.2 composites with equiaxed and Widmanstätten microstructure matrixes were prepared by sintering amorphous and crystalline powder, respectively. The alloy with Widmanstätten structure exhibits lower yield and fracture strengths at ambient temperature but higher values at elevated temperatures compared with that with equiaxed structure. Microscopic deformation mechanisms of the alloys with different microstructures were investigated by scanning electron microscope (SEM), transmission electron microscope (TEM) and numerical simulation. The results indicate that the profuse dislocation pile-ups and formation of nanotwins in the β-Ti matrix contribute to the high room-temperature strength and plasticity of the composite with equiaxed β-Ti structure matrix, while stress concentration and cracking in the interior of acicular (Cu, Ni)Ti2 phases in Widmanstätten structure matrix deteriorates plastic deformation capacity of the alloy. The higher strength and plasticity for the composite with Widmanstätten structure matrix at elevated temperature is ascribed to dislocation pile-ups around grain boundaries of β-Ti and acicular (Cu, Ni)Ti2 phases and the curving of acicular (Cu, Ni)Ti2 phases inside Widmanstätten structure matrix. The results obtained provide some guidelines to design high-temperature alloy with excellent properties for structural applications.