Strength of iron under pressure up to 55 GPa from X-ray diffraction line-width analysis

The X-ray diffraction patterns are recorded from polycrystalline iron sample compressed in a diamond anvil cell up to 55 GPa. The maximum micro-stress in the sample, a measure of compressive strength, is derived from the line-width analysis. The strength of iron in the body centered cubic (BCC)-phase is 1.1±0.2 GPa. This value is in good agreement with the strength derived from the hardness vs. grain-size data. The strength increases steeply during the BCC–hexagonal closed packed (HCP) transition. The strength–pressure data for HCP-iron fit the relation σ=2.9+0.028Pσ=2.9+0.028P, where σ and P are the compressive strength and pressure in GPa, respectively. The present results agree well with those obtained from the line shift analysis carried out in earlier studies.