DTA/HF-DSC analysis of ternary systems, heat capacity
measurements using DSC,
Other dynamic methods Phase diagram of ternary system and DTA
Application of DTA for vertical section construction TGA mass
change measurement Heat capacity measurement using DSC Dilatometry
DTA analysis of ternary systems
Composition 1: Al-0.5%Fe-6 % Cu Equilibrium solidification-black
line LL+fccL+fcc+aL+fcc+a+b(U) L+fcc+b Scheil solidification red
line L+fcc+bL+fcc+b+(E) Composition 2: Al-0.5%Fe-20 % Cu
Equilibrium and Scheil (the same sequence of transformations)
LL+fccL+fcc+bL+fcc+b+(E) Types of reactions in ternary system
Sn E2: LAg3Sn+(Sn)+Cu6Sn5 U5:L+Cu3Sn Ag3Sn+Cu6Sn5 P2:
L+(Ag)+Cu10Sn3 Cu3Sn DTA for ternary systems: Example Al-Fe-Cu
(composition Al-6%Cu-0.5%Fe)
L+fcc+b L+fcc+a L+fcc+b L+fcc+a+b L+fcc+a L+fcc L+fcc+b+q L+fcc DTA
and dHs/dTs plots under equilibrium conditions DTA and dHs/dTs
plots under Scheil conditions DTA for ternary systems: Example
Al-Fe-Cu (composition Al-20%Cu-0
DTA for ternary systems: Example Al-Fe-Cu (composition
Al-20%Cu-0.5%Fe) L+fcc+b+q L+fcc+b 1. Ternary invariant transition
reactions (U-type) may have quite different DTA signal compared to
ternary eutectic reaction. This depends how cooling occurs by
equilibrium or non-equilibrium procedure. 2. Microstructure
investigation before and after melting can help to interpret DTA
results L+fcc DTA and dHs/dTS plots for Al-20%Cu-0.5%Fe under
equilibrium conditions Example: system Ag-Cu-Sn
Part of liquidus surface U5 L+Cu3Sn=Ag3Sn+Cu6Sn5, E2
L=Ag3Sn+(Sn)+Cu6Sn5 Phase fraction diagram Sn-25%Ag-10%Cu Vertical
section at 25 mass% Ag Latent heat release in equilibrium Latent
heat release in Scheil conditions dH/dT in equilibrium Example
Ag-Cu-Sn Phase fraction Sn-25%Ag-27%Cu
Latent heat release in equilibrium dHS/dT in equilibrium Latent
heat release in Scheil conditions Vertical section construction
using DTA/DSC Vertical section construction using DTA/DSC
Concluding remarks Temperature of sample thermocouple is different
from sample temperature. The temperature ranging from on-set to
peak is not due to kinetics but due to heat transfer between
sample, crucible and thermocouple. The deviations from full
equilibrium can and do occur duringthe melting and freezing of
alloy sample at the rates encountered in DTA. The loss of full
equilibrium is due to slow rate of solute diffusion in alloys and
can be modelled by Scheil approach. Using DTA temperature and heat
effect of melting or solid phase transformation of alloys/compound
can be determined. Interpretation of DTA results for multicomponent
system is very complex task especially taking into account non
fully equilibrium processes. Combination with other methods like
XRD and SEM/EDX before and after DTA is necessary to interpret the
results obtained by thermal analysis. TGA: Thermo Gravimetric
Analysis
Determination of the mass as function of temperature. It is
applicable for all reaction involving gas phase Decomposition
reactions Vaporization and sublimation Desorption Oxidation and
reduction Corrosion Small sample Gas flow essential Different
temperature modes Linear heating, isothermal, stepwise isothermal
Solid lines- TG, dashed lines - DTG DTA/TGA combination
Identification of intermediate reactions
Determination of reaction temperature Temperature calibration of
the instrument Example :the ZrO2-MnO-Mn2O3 system Pure MnO sample
778C 3Mn2O3 2aMn3O4+0.5O2 1167C aMn3O4 bMn3O4 1458C bMn3O4
3MnO+0.5O2 ZrO2-30%MnO Below 1000C F M and Mn2O3 aMn3O4+O2 1122C
aMn3O4bMn3O4 1200C beginning bMn3O4 MnO+O2 1193C M T 1295C T F
1404C end ofbMn3O4 MnO+O2 1573C melting L MnO+F Differential
Scanning Calorimetry (DSC)
Linear heating rate Stationary heat flow(FFS, FFR F furnace, S-
sample, R reference) A thermal reaction causes a deviation from
stationary conditions Evaluation is possible if reaction heat flow
rate Fr ~DTSR Conditions Fr