PM DR KHAIREL : THERMAL ANALYSIS : METALS

Instrumentation

The sample is clamped in the measurement
head of the DMA instrument.
During measurement, sinusoidal force is
applied to the sample via the probe.
Deformation caused by the sinusoidal force is
detected and the relation between the
deformation and the applied force is
measured.
Properties such as elasticity and viscosity are
calculated from the applied stress and strain
plotted as a function of temperature or time.

• DMA is used for measurement of various

types of materials using different

deformation modes:
• tension, compression,
• dual cantilever bending,
• 3-point bending and
• shear modes
• The most suitable type should be selected

depending on the sample shape, modulus

and measurement purpose.

DMA Deformation modes Viscoelastic properties such as:
-Storage modulus: E', G' (purely elastic
component)
-Loss modulus: E", G" (purely viscous
component)
-Loss tangent: tanδ (=E"/E'),

Dynamic Mechanical Analysis (DMA)

 DMA is simple describes as applying an oscillating force to a
sample and analyzing the material’s response to that force

Applied force » σ
Response » ε (or δ)

What does DMA measure?

1)The material is characterized in terms of its
• modulus
•elasticity
•viscosity
•damping behavior
•glass transition temperature

2)Changes of these with
•strain
•strain rate
•temperature
•oscillatory frequency

3)Modulus

Dynamic Mechanical Analysis (DMA)

Figure:
 (a) When a sample is subjected to a sinusoidal oscillating stress, it responds in a similar

strain wave provided the material stays within its elastic limits.
 (b) When the material responds to the applied wave perfectly elastically, an in-phase,

storage, or elastic response is seen.
 (c) While a viscous response gives an out of phase, loss, or viscous response
 (d) Viscoelastic materials fall in between these two extremes. For the real sample in (d),

the phase angle, δ and the amplitude at peak, k are the value used for the calculation of
69 modulus, viscosity, damping and other properties.

Dynamic Mechanical Analysis (DMA)

 Dynamic stress

What does DMA measure?

DMA measures stiffness and damping, these are
reported as modulus and tan delta. Because
sinusoidal stress is applied, modulus can be
expresesed as;

• in-phase component, the storage modulus (E‘) and
• out of phase component, the loss modulus (E")

Storage modulus (E‘) is a measure of elastic response
of a material. It measures the stored energy.

Loss modulus (E") is a measure of viscous response of
a material. It measures the energy dissipated as heat.

Tan delta, (Tan δ) is the ratio of loss to the storage and is called damping. It is a
measure of the energy dissipation of a material. It tells us how good a material will
be at absorbing energy.

Basically tan delta can be used to characterize the modulus of the material. Delta
(δ) should range between 0° and 90° and as delta approaches 0° it also approaches
a purely elastic behaviour. As delta approached 90° the material approaches a
purely viscous behaviour.

The tan of delta is defined below: • Increasing Tan δ indicates that your material has
more energy dissipation potential so the greater
tan δ = E"/E' the Tan δ , the more dissipative your material is.

E" = storage modulus • Decreasing Tan δ means that your material acts
E' = loss modulus more elastic now and by applying a load, it has
more potential to store the load rather than
dissipating it!



How to run alloys in DMA

• The simple test to be carried out is the three point bending
mode using a dual cantilever system.

• The composite specimens will be prepared in the form of
rectangular bars with dimensions of 50 x 10 x 1mm.

• The tested specimens are run at 2 oC/ min heating rate from
30 to 400 oC at 10 Hz in a flowing purified nitrogen gas.

• In many case, frequency can be adjusted from 0.1 to 40 Hz
depends on many factors. The result will be plotted in terms
of storage modulus, loss modulus and damping capacity
versus temperature (as common plot).

DMA Graph

 A typical response from a DMA shows both modulus and Tan δ. As the
material goes through its glass transition, the modulus reduces and the Tan δ
goes through a peak.

 TTagninδdcicuartveed. by major change in curves: Large drop in log E’ curve and Peak in

Example 1 : Damping behaviour of aluminite (Al2SO4(OH)4·7H2O)
particulate reinforced ZA-27 alloy metal matrix composites

(a) Storage modulus vs. temperature at 10 Hz, (b) loss modulus vs. temperature at 10 Hz,
and (c) specific damping capacity vs. temperature at 10 Hz.



• ZA-27 based metal matrix composites (MMCs)
have been prepared with 1, 2, 3, and 4% of
reinforcement by the compocasting method.
The damping behavior and dynamic Young’s
modulus of base alloy and the particulate
reinforced composites were studied over a
temperature range of 30–300°C using a
dynamic mechanical analyser at 10 Hz.

• The damping capacity of the materials was
observed to increase with the increase in
temperature whereas the dynamic modulus
was found to decrease with the increase in
temperature. Both damping capacity and
dynamic modulus increase with an increase
in wt.% of reinforcement being more
remarkable in the higher temperature range.

• The contribution of aluminite particulate to
the overall MMC damping may be related to
the increase in dislocation density in the
matrix as a result of thermal strain mismatch
between the ceramic particulate and ZA-27
matrix

Example 2 : Damping behaviour of AlMg5/SiC/PLZT metal matrix

composite produced by hot extrusion lead lanthanum zirconate titanate (PLZT)

Fig. 5 : Tan δ versus temperature of (a) Matrix (black
color), (b) SE1 (gray color), (c) SE2 (green color), (d) SE3
(blue color) and (e) SE4 (red color).

Fig. 6 : Storage modulus versus temperature of (a)
Matrix (black color), (b) SE1 (gray color), (c) SE2
(green color), (d) SE3 (blue color) and (e) SE4 (red
color)

• A novel type of piezoelectric aluminium-based hybrid composite containing silicon

carbide (SiC) and piezoelectric lead lanthanum zirconate titanate (PLZT) was
prepared using powder metallurgy technique followed by sintering at 630 °C and
hot extrusion at 500 °C. The volume fraction of PLZT particles varied as 0%, 5%,
10% and 15% with fixed weight 1 wt.% of SiC respectively in the composite.
• Fig. 5, Fig. 6 presents tangent of the phase angle (Tan δ) and the storage modulus

(E′) for matrix and composites at different temperatures between 25 and 400 °C at
1 Hz. Both parameters were notably affected by the temperature in these
composites.
• Tan δ (Fig. 5) curves remain steady between room temperature to 100 °C, however,
above this temperature damping capacities increase with increasing temperature.
An increase of damping capacity values was significant for samples with

piezoelectric particles, and increasing weight percentage of piezoelectric particles
demonstrate an significant increase in the value of Tan δ.
• DMA storage modulus curves of the composite are presented in Fig. 6. A decrease
in mechanical properties is observed for all samples. At 100 °C, aluminium matrix
sample has a storage modulus close to 50 GPa while, at the same temperature,

sample reinforced with 15 wt.% of piezoelectric has 68 GPa. This suggests that high
mechanical properties could be reached in multifunctional hybrid AlMg5/PLZTp/SiCp
composites.

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THERMAL ANALYSIS

Dilatometer (DIL)

Dilatometry is a technique that measures
change in length, sample temperature
and furnace temperature to facilitate the
measurement of the coefficient of
thermal expansion (CTE), softening
point, determination of phase and
glass transitions.

What is dilatometer ?

• A dilatometer is a scientific instrument (high precision systems)
designed to measure dimensional changes caused by a physical or
chemical process due to thermal environment.

• Solids mostly expand in response to heating and contract on cooling.
This response to temperature change is expressed as its coefficient
of thermal expansion.

• To measure thermal expansion (Indicative how materials expands
upon heating).
– Linear thermal expansion
– Volume
• To determine coefficient of thermal expansion
• To confirm thermal expansion mismatch
• To evaluate sintering process of ceramic, metals.
• To obtain sintering temperature and shrinkage steps
• To observe dimensional changes during chemical reactions and
phase transformations

Thermomechanical analysis
instrument

• Dilatometer are made with a Thermomechanical
analyzer

• consisting of a specimen holder and a probe
that transmits changes in length to a
transducer that translates movements of the
probe into an electrical signal.

• The apparatus also consists of a furnace for
uniform heating, a temperature-sensing
element, calipers, and a means of recording
results.

Thermal Expansion

Materials change size when temperature
is changed

 initial Tinitial Tfinal > Tinitial
 final Tfinal

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Coefficient of Thermal Expansion (CTE)

• The CTE is also closely related to crystal
structure, grain size and bond strength.

• Materials with a less dense, open structure, a
small grain size and high bond strength have the
lower CTE.

• The thermal expansion of materials arises due to
the an harmonicity in inter-atomic interactions.

• Thermal expansion in material is directly related to strength of
the forces between the molecules or atoms. Material with
stronger forces for instant harder materials will have lower
thermal expansion. Diamond is a very hard material due to its
strong covalent bonding and has much lower CTE than softer
material such as steel.

Atomic Perspective: Thermal Expansion

Thermal expansion arises from an increase in the average distance between the atoms

Asymmetric curve: Symmetric curve:
-- increase temperature, -- increase temperature,
-- increase in interatomic -- no increase in interatomic

separation separation
-- thermal expansion -- no thermal expansion

12

Coefficient of Thermal Expansion: Comparison

increasing  Material -6

• Polymers  (10 /C) 10

Polypropylene 145-180
106-198
Polyethylene 90-150
126-216
Polystyrene
23.6
Teflon 12
• Metals 4.5
14.2
Aluminum
Steel 13.5
Tungsten 7.6
Gold 9
• Ceramics 0.4
Magnesia (MgO)
Alumina (Al2O3)
Soda-lime glass
Silica (cryst. SiO2)

Units

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Example 1 : Effects ooffWCCr3–CC2oamndateVrCialos.n • In this investigation, the sintering processes of Cr3C2
and VC doped submicron WC–Co powders were
the sintering behavior
studied by using dilatometry.
• Fig. illustrates the different consolidation behavior of VC and

Cr3C2 doped WC–Co during heating to 1300 °C before liquid
formation.
• There is no observable shrinkage for either VC or Cr3C2
doped WC–Co until the temperature reaches 900 °C, where

onset of densification begins. Both VC and Cr3C2 doped WC–
Co show rapid densification after 1100 °C.
• Differences between VC and Cr3C2 doped WC–Co lie in the
900 °C–1100 °C temperature range.

• The shrinkage curve of Cr3C2 doped WC–Co shows a
smooth transition from onset of densification to rapid

densification between 900 °C and 1100 °C.
• However, the shrinkage curve of VC doped WC–Co

shows an inflection between 900 and 1100 °C,

indicating rapid shrinkage between 900 °C and 1000 °C

with shrinkage slowing after 1000 °C.

Dilatometer curves of VC and Cr3 C2 doped submicron WC–Co

materials. Vanadium carbide Chromium carbide

Example 2 : Negative thermal expansion property of β-Cu2V2O7

• β-Cu2V2O7 is prepared by using the solid-state method. We
discuss that β-Cu2V2O7 exhibits large negative thermal
expansion property over a wide temperature range and no
phase change occurs.

• The relative length change of β-Cu2V2O7 within the
temperature RT–673 K were obtained with LINSEIS DIL L76
thermal dilatometer and displayed in Figure

• The solid and red doted lines indicated the test and linear
fitting results, respectively. The relative length change curve
was smooth with no variation and presented a monotonous
trend in the temperature range of RT–673 K. The average
linear expansion coefficient of β-Cu2V2O7 was
−20.2 × 10−6 K−1.

Relative length (%) changes of the sample within the
temperature range of RT to 673 K.

The underlying mechanism of the negative thermal
expansion of β-Cu2V2O7 involves the coupling effect of the
tetrahedron caused by the lateral vibration of the bridge
oxygen atom and tensile effect of the tetrahedron. The
partial collapse caused by the loss of oxygen atoms is also
crucial in this mechanism.

(a) Diagram of β-Cu2V2O7 (b) Diagram of [V2O7] structural unit.

Example 3 : Coefficient of thermal expansion (CTE) of Cu-B/diamond composites

prepared by gas pressure infiltration

• Cu-B matrix composites reinforced with diamond particles
(Cu-B/diamond) were prepared by gas pressure infiltration
(GPI). The effect of boron addition in the range of 0–1.0 wt%
on the thermal expansion behavior of the Cu-B/diamond
composites was evaluated.

• The coefficient of thermal expansion (CTE) of the Cu-
B/diamond composites initially decreases and then
increases with increasing boron content (x=1.0).

• With the addition of boron in the Cu matrix, the CTE values of
the Cu-xB/diamond composites are significantly reduced. The
Coefficient of thermal expansion of the Cu-xB/diamond addition of boron (CTE of 6.4 × 10−6/K) reduces the CTE of the
composites produced by gas pressure infiltration. composite. More importantly, as seen from the
microstructural features, the formation of carbides at the
interface effectively enhances the interfacial bonding
between Cu and diamond. It thus lowers the CTE values,
since sound interfacial bonding can effectively exert the
effect of extremely hard diamond particles to restrain the
expansion of metal matrix