B D Zhou

Superplasticity of stoichiometric NiAl with large grains

acad sinica, inst met res, dept superalloys & intermetall, shenyang 110015, peoples r china. harbin inst technol, dept mat sci & engn, harbin 150001, peoples r china.;guo, jt (reprint author), acad sinica, inst met res, dept superalloys & intermetall, shenyang 110015, peoples r china

Superplastic behavior in pseudo-eutectic NiAl-9Mo alloy

The superplastic behavior and deforming mechanism for polycrystalline NiAl-9Mo alloy with a two-phase microstructure consisting of a dispersion of alpha-Mo phase in a beta-NiAl matrix are investigated in this paper. The alloy exhibits superplastic elongations as high as up to 180% under an initial strain rate of 1.11 x 10(-4) s(-1) at 1373 K with strain rate sensitive index of 0.56. Grain boundary sliding and rotation of beta-NiAl matrix is responsible for superplastic deformation in this alloy. The premature fracture stems from serious cavitation occurring during the deformation process. The superplastic deformation behavior is similar to that of single-phase intermetallics, such as Ni3Al, Ni3Si and Co3Ti

Flow behavior and mechanisms of NiAl-9Mo alloy during superplastic deformation

The superplastic deformation of the as-extruded NiAl-9NIo eutectic alloy is observed as a function of temperature and strain rate, and characterized by the constitutive equation and the deformation microstructure. In the region of high strain rate (and low temperature), the flow curve exhibits a stress peak followed by weak softening, and then by a dynamic restoration (DR) process. The activation energy of deformation in this region is estimated to be Q = 207 kJ/mol, similar to that of bulk diffusion in NiAl. It is suggested that the mechanism associated with DR is responsible for the deformation in this region. In the region of low strain rate (and high temperature) the flow curve exhibits continuous work hardening until fracture, and concomitant grain boundary sliding and grain growth occur. The activation energy of deformation in this region is estimated to be Q = 113 kJ/mol suggestive of grain boundary diffusion in NiAl. Larger tensile elongation, i.e., superplastic deformation, is observed in the latter region