Modeling High Strain Rate Plasticity in BCC Lead*

High-energy lasers enable determination of metal strength at very high pressures. Here we consider the strength (flow stress) of lead in the high-pressure body-centered cubic (bcc) phase at a peak pressure of ∼400 GPa. Two previous models of Pb strength were built from the low-pressure fcc phase. Plasticity in bcc and fcc crystals can be very different. Experiments conducted at the National Ignition Facility have used ramp-compression to drive Rayleigh-Taylor instability and measured the ripple growth to infer strength in the bcc phase of lead and lead alloy [1]. We have developed an Improved Steinberg-Guinan model for bcc lead strength [2] using ab initio calculations of the shear modulus at pressure that agrees well with those experiments. The alloying, which increases strength 4x at ambient conditions, has no measurable effect at high-pressure.
[1] A. Krygier et al., Phys. Rev. Lett., to appear (2019).
[2] Robert E. Rudd et al., AIP Conf. Proc. 1979, 070027 (2018)