An analysis of cavity nucleation in superplasticity

The influence of rolling direction on the mechanical behavior and formation of cavity stringers in the superplastic Zn-22% Al alloy

Activation energy for superplastic deformation of in718 superalloy

An Al–33% Cu eutectic alloy was processed by high-pressure torsion (HPT) at a pressure of 6.0 GPa for 1/4 to 10 turns. Examination after processing showed a gradual evolution to a reasonable level of hardness and microstructural homogeneity after 5 or more turns. Tensile tests were conducted at a temperature of 723 K on specimens processed through 5 and 10 turns of HPT. These specimens exhibited excellent superplastic properties with a maximum elongation of ∼1250% at strain rates lower than 10−3 s−1. The results also showed that the maximum elongation is displaced to a faster strain rate when the HPT processing is conducted to a higher number of turns. An analysis demonstrates that superplastic flow in the Al–Cu alloy processed by HPT is well described by a theoretical relationship that was developed for conventional superplastic materials.

Development of hardness homogeneity and superplastic behavior in an aluminum–copper eutectic alloy processed by high-pressure torsion

Experiments were conducted on the Al-33% Cu eutectic alloy in both an annealed and an as-extruded condition. For both conditions, the relationship between flow stress and strain rate is sigmoidal with maximum ductilities occurring at intermediate strain rates in the superplastic Region II. Specimens fail by necking at the faster strain rates in Region III, but the severity of necking is reduced with decreasing strain rate and the necks are very diffuse in Region II. There is extensive internal cavitation in the fractured specimens, especially at lower strain rates and in the vicinity of the fracture tip. It was observed that cavities form preferentially on theα-θ interphase boundaries. It is shown by calculation that the observed change from small rounded cavities to large cavities elongated along the tensile axis is reasonably consistent with the theories of cavity growth in fine-grained superplastic alloys

B.P. Kashyap

Papers

Activation energy for superplastic deformation of an AlCu eutectic alloy

Evidence for cavitation during superplastic deformation of an AlCu eutectic alloy