Experimental observations on microstructure of iron and other metals at high pressures and temperatures*

Materials subjected to high pressure (P) and high/low temperature (T) treatments in the diamond anvil cell (DAC) often exhibit complexity and inhomogeneity, on length scales ranging from nanometers to tens of microns. A recently developed ability to perform detailed spatially resolved characterizations of the inhomogeneity under high P, or in the high P-T treated samples, has allowed to unlock some of the complexity and to gain an understanding of several of emerging physical phenomena in high pressure sciences.
One of the examples discussed here will be the crystal structure of iron (Fe) in the Earth’s inner core, which remains debated. Experimental evidence, based in part on spatially resolved microstructure analysis, shows a bcc-Fe appearing at P-T conditions approaching the Earth’s inner core. Recent results on the microstructure and phases of compressed zirconium metal will be discussed as well.