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