Melting Behavior of Iron Alloys

Earth's core consists of an iron-nickel alloy with approximately ten percent of other light elements (e.g., C, S, Si, O). Therefore, the behavior of iron alloys of similar composition at the temperatures and pressures that resemble the conditions of Earth's core is of fundamental importance to our understanding of the inner workings of our planet. The melting behavior of iron alloys is especially important as it sheds light on the conditions at the boundary between Earth's solid inner core and its liquid outer core, as well as puts constraints on the age of the inner core. Here, we report the melting curve of iron alloys based on laser-heated diamond anvil cell experiments. Four-color multi-wavelength imaging radiometry is used to determine the temperature profiles of the heated spot during melting and electron microscopy is used to map the compositional and textural changes of the iron alloys. An automated analysis of the texture, composition and temperature of the hot spots is conducted with an in-house developed image processing script, which identifies the melting point of the alloys and the preferred host phases of minor elements (e.g., Ni, Cr, Mn) at high-pressure/temperature conditions.