Dilatometry — Metrology Testing Service
What Is Dilatometry?
Dilatometry is a precision thermal analysis technique that measures the dimensional changes — expansion or contraction — of a material as a function of temperature or time. These dimensional changes, expressed as linear or volumetric coefficients of thermal expansion (CTE), are fundamental material properties that govern how components perform under thermal cycling, fit within assemblies, and behave during manufacturing processes such as sintering, heat treatment, and casting.
In metrology and materials testing, dilatometry provides essential data for material selection, process validation, quality control, and failure analysis across a broad range of industries.
Principle of Dilatometry
When a material is heated, its atomic lattice vibrates with greater amplitude, causing the material to expand. Upon cooling, it contracts. Dilatometry measures this dimensional change with high precision — typically to within a few nanometers — using a push-rod or optical sensing mechanism. The resulting dilatometric curve plots dimensional change (ΔL/L₀) versus temperature, revealing not only the CTE but also phase transformation temperatures, sintering shrinkage, and other thermally induced microstructural events.
Types of Dilatometers
Push-Rod Dilatometer
The most commonly used type is in industrial and research laboratories. A push-rod in physical contact with the sample transmits its dimensional change to a high-resolution displacement sensor (LVDT or capacitive sensor). Available in vertical and horizontal configurations for different sample geometries and temperature ranges.
Optical Dilatometer
A non-contact method using a camera and a light source to measure dimensional changes by imaging the sample’s shadow or silhouette. Ideal for soft, fragile, or reactive materials that cannot sustain the mechanical contact of a push-rod system. Widely used for powders, sintered parts, and molten materials.
Laser Dilatometer
Uses laser interferometry to achieve the highest-precision measurements of thermal expansion, especially for low-expansion materials such as Invar alloys, ceramics, and optical components, where even nanometer-scale accuracy matters.
Key Measurements from Dilatometry
Coefficient of Thermal Expansion (CTE): The primary output — quantifying how much a material expands or contracts per degree of temperature change. Essential for designing assemblies with dissimilar materials, thermal cycling components, and precision instruments.
Phase Transformation Temperatures: Dilatometric curves reveal sudden slope changes corresponding to solid-state phase transformations—for example, the austenite-to-martensite transformation in steel or the alpha-to-beta transition in titanium alloys.
Sintering Shrinkage: In ceramics and powder metallurgy, dilatometry tracks the densification and shrinkage that occur during sintering, enabling the optimization of sintering profiles and the prediction of final dimensions.
Glass Transition and Softening Points: In glass and polymer science, dilatometry identifies the temperature at which the dimensional behavior of a material shifts — a critical parameter for processing and service temperature determination.
Industry Applications
Aerospace and Defense: CTE matching between dissimilar materials in turbine assemblies, thermal barrier coatings, and structural composites is critical to preventing delamination and fatigue cracking during thermal cycling.
Automotive: Engine components, exhaust systems, and brake discs undergo dilatometric characterization to ensure dimensional stability over the full operating temperature range.
Electronics: Printed circuit boards, semiconductor packages, and solder joints require precise CTE data to prevent thermally induced stress and fatigue failure in service.
Steel and Metals: Phase transformation temperatures identified by dilatometry guide the design of heat treatment cycles (quenching, tempering, annealing) to achieve targeted microstructures and mechanical properties.
Ceramics: Dilatometry is indispensable for optimizing sintering profiles, predicting final dimensions of fired ceramics, and matching CTEs between ceramic and metal components in joined assemblies.
Standards and Compliance
Dilatometric testing is governed by standards including ASTM E228 (linear thermal expansion of solid materials by push-rod dilatometer), ASTM E289 (linear thermal expansion of rigid solids with interferometry), ISO 11359-1, and ISO 11359-2, ensuring measurements are traceable, reproducible, and accepted globally.
Conclusion
Dilatometry provides precise thermal expansion and phase transformation data that engineers need to design assemblies with dissimilar materials, optimize heat-treatment cycles, and predict sintering shrinkage in ceramics and powder-metallurgy components. Whether measured by push-rod, optical, or laser interferometry per ASTM E228 and ISO 11359, accurate CTE data is what prevents thermally induced stress failures in aerospace structures, electronics packages, and automotive components subjected to repeated thermal cycling throughout their service life.
Why Choose Infinita Lab for Dilatometry Testing?
At the core of Infinita Lab’s breadth is a network of 2,000+ accredited labs in the USA, offering access to over 10,000 test types. From advanced metrology, including dilatometry, TMA, and SEM, to mechanical, environmental, and standardized ASTM/ISO testing, we give clients unmatched flexibility, specialization, and scale. You’re not limited by geography, facility, or methodology — Infinita connects you to the right testing, every time.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote.
Frequently Asked Questions
What is the difference between dilatometry and TMA? Dilatometry primarily measures free thermal expansion or contraction under zero or minimal load, while Thermomechanical Analysis (TMA) measures dimensional changes under a defined applied load, enabling characterization of creep, penetration, and viscoelastic behavior.
What materials can be tested by dilatometry? Dilatometry can test metals, alloys, ceramics, glasses, polymers, composites, and sintered powders. Sample form can be solid rods, cylinders, plates, or pellets depending on the instrument configuration.
Which ASTM standard governs push-rod dilatometry? ASTM E228 governs linear thermal expansion testing of solid materials using a push-rod dilatometer, and ASTM E289 covers interferometric measurements for more precise low-expansion measurements.
Why is CTE important for electronics packaging? CTE mismatch between a chip (silicon), substrate (ceramic or polymer), and solder joint causes differential expansion during thermal cycling, generating fatigue stresses that lead to solder joint cracking and device failure. Dilatometry provides the CTE data needed to minimize this mismatch.
Can dilatometry detect phase transformations in steel? Yes. Phase transformations such as the austenite-to-martensite and austenite-to-pearlite transformations in steel produce distinct slope changes in the dilatometric curve, allowing precise determination of transformation start and finish temperatures.
