Compression of silver in a diamond anvil cell: Pressure dependences of strength and grain size from X-ray diffraction data

Two silver samples, coarse grained (c-Ag, grain size 300730 nm) and nanocrystalline (n-Ag, grain size 5576 nm), are compressed in a diamond anvil cell in separate experiments. The pressure is increased in steps of 3 GPa and the diffraction pattern recorded at each pressure. The grain size and compressive strength are determined from the analysis of the diffraction line-widths. The grain size of c-Ag decreases rapidly from 300730 nm at ambient pressure to 4078 nm at 15 GPa, and then gradually to 2073 nm at 40 GPa. After pressure release to ambient condition, the grain size is 2574 nm. The strength at ambient pressure is 0.1870.05 GPa and increases to 1.070.3 GPa at 40 GPa. The grain size of n-Ag decreases from 5576 nm at ambient pressure to 1774 nm at 15 GPa and to 1473 nm at 55 GPa. After release of pressure to ambient condition, the grain size is 5077 nm. The strength increases from 0.5170.07 GPa at ambient pressure to 3.570.4 GPa at 55 GPa. The strength is found to vary as the inverse of the square-root of the grain size. The results of the present measurements agree well with the grain-size dependence of strength derived from the hardness versus grain size data at ambient pressure available in the literature. & 2010 Elsevier Ltd. All rights reserved.