Determination of Thermal Expansion Coefficient in TRIP Steel, Mg–Li Alloy and Si + SiC Coatings

Abstract—Using high-temperature X-ray diffraction, the thermal expansion coefficient was determined in VNS9Sh steel, Mg-8Li-1Al alloy, and Si+SiC multilayer coating layer. The TCLE value of the γ phase significantly exceeds the TCLE of the α phase, which corresponds to the data for austenitic and martensitic steels, while the TCLE values of each phase depend on the composition of phases. The TCLE value in the β phase of a magnesium alloy exceeds the TCLE value for the α phase, and this difference increases with an increase in temperature. The TCLE value of the α phase in the direction of the “c” axis (α_c) is higher than in the basal plane (α_a). It is shown that the advantage of the high-temperature X-ray diffraction method for assessing the TCLE is the ability to measure them in thin surface layers, as well as the ability to evaluate the TCLE of individual phases and their anisotropy in multiphase, textured objects.