A review of measurement techniques for the thermal expansion coefficient of metals and alloys at elevated temperatures

Abstract

Metallurgical operations at elevated temperatures, such as those that involve solidification and/or mechanical deformation, can be critically influenced by the thermal stresses and strains that result from expansion and contraction of the material as a function of temperature. With the increasing use of computer-based process models for these operations, there arises a greater need for quantitative data on the thermal expansion coefficient of the relevant alloy at the temperatures involved. After briefly reviewing some existing sources of data for this property, the various techniques for its measurement at elevated temperatures are then described. These include mechanical dilatometry, optical imaging and interference systems, x-ray diffraction methods and electrical pulse heating techniques. Finally the implications, for process modelling, of the available data and measurement techniques are discussed.

A new method for the determination of the coefficient of thermal expansion of solid materials

“…Often the lower limit of the specified temperature range is also used as the reference temperature, leading to a modification of the former equation to the following [3]:…”

“…Standard methods include mechanical dilatometry [1], laser interferometry [2] and high magnification optical imaging [3]. The increasing use of computer-based thermo-mechanical models as well as specific requirements concerning anisotropic materials has determined in the last few years a greater need for quantitative data, promoting the development of new full-field optical measurement techniques, such as those based on Electronic Speckle Pattern Interferometry (ESPI) [4][5], phase-shifting interferometry [6] and digital image correlation [7].…”

New advances in the laboratory characterization of refractories: testing and modelling

“…Classic dilatometers are routinely used and, due to their high accuracy, allow the coefficient of thermal expansion, shrinkage induced by sintering, glassing transition, and chemical changes to be determined. Contactless optical instruments have pushed the temperature limit back and therefore can be used to melt samples during the measurement [20,21]. However, the sample size limitation of a few millimetres makes tests difficult on very heterogeneous materials that are made of aggregates of a few millimetres and, therefore, require large representative volumes.…”

High Temperature Oxidation Resistance of Ni22Cr11Al Bond Coat Produced by Spark Plasma Sintering as Thermal Barrier Coatings

“…From thermodynamic point of view Al has high affinity to react with 0 2 , which brings about O 2 penetration and Al diffusion gives rise to Al 2 O 3 formation [34][35][36]. EDS investigation XRD patterns through the cross section of the bond coat after oxidation at 1100°C for 100 hr, revealed the oxides phases in the bond coat are NiCr 2 O 4 , NiCrO 3, NiCrO4, and NiO [37].…”