Shear modulus of shock-compressed LY12 aluminium up to melting point

Asymmetric plate impact experiments are conducted on LY12 aluminium alloy in a pressure range of 85-131 GPa. The longitudinal sound speeds axe obtained from the time-resolved particle speed profiles of the specimen measured with Velocity Interferometer System for Any Reflector （VISAR） technique, and they are shown to be good agreement with our previously reported data of this alloy in a pressure range of 20-70 GPa, and also with those of 2024 aluminium reported by McQueen. Using all of the longitudinal speeds and the corresponding bulk speeds calculated from the Gruneisen equation of state （EOS）, shear moduli of LY12 aluminium alloy are obtained. A comparison of the shear moduli in the solid phase region with those estimated from the Steinberg model demonstrate that the latter are systematically lower than the measurements. By re-analysing the pressure effect on the shear modulus, a modified equation is proposed, in which the pressure term of P/η^1/3 in the Steinberg model is replaced by a linear term. Good agreement between experiments and the modified equation is obtained, which implies that the shear modulus of LY12 aluminium varies linearly both with pressure and with temperature throughout the whole solid phase region. On the other hand, shear modulus of aluminium in a solid-liquid mixed phrase region decreases gradually and smoothly, a feature that is very different from the drastic dropping at the melting point under static conditions.

Shear modulus of shock-compressed LY12 aluminium up to melting point

Asymmetric plate impact experiments are conducted on LY12 aluminiumalloy in a pressure range of 85--131,GPa. The longitudinal soundspeeds are obtained from the time-resolved particle speed profiles ofthe specimen measured with Velocity Interferometer System for AnyReflector (VISAR) technique, and they are shown to be good agreementwith our previously reported data of this alloy in a pressure rangeof 20--70,GPa, and also with those of 2024 aluminium reported byMcQueen. Using all of the longitudinal speeds and the correspondingbulk speeds calculated from the Gruneisen equation of state (EOS),shear moduli of LY12 aluminium alloy are obtained. A comparison ofthe shear moduli in the solid phase region with those estimated fromthe Steinberg model demonstrate that the latter are systematicallylower than the measurements. By re-analysing the pressure effect onthe shear modulus, a modified equation is proposed, in which thepressure term of $P/eta^{1/3}$ in the Steinberg model is replaced bya linear term. Good agreement between experiments and the modifiedequation is obtained, which implies that the shear modulus of LY12aluminium varies linearly both with pressure and with temperaturethroughout the whole solid phase region. On the other hand, shearmodulus of aluminium in a solid-liquid mixed phrase region decreasesgradually and smoothly, a feature that is very different from thedrastic dropping at the melting point under static conditions.