The cavity volume fraction in superplastically deformed aluminum alloy from photoacoustic signal was calculated by using two kinds of effective medium theories(Maxwell-Garnet theory and Bruggeman theory) and Rosencwaig-Gersho model. Two models exhibited similar dependence on photoacoustic signal at lower volume fraction than 15%, but the difference became significant as volume fraction increased further.
Cavity volume fraction along tensile axis showed a larger value near the shoulder part than the center, however cavity volume fraction in failured samples had large value near the fracture tip. Cavity volume fraction increased as the strain increased, however it was difficult to estimate total cavity volume fraction because of local variation due to inhomogeneous strain of specimen.
