INFLUENCE OF Ce ADDITION ON SOLIDIFICATION AND MECHANICAL PROPERTIES OF AlSi10Mg ALLOY

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1 University of Ljubljana Faculty of Natural Science and Engineering Department for Materials and Metallurgy INFLUENCE OF Ce ADDITION ON SOLIDIFICATION AND MECHANICAL PROPERTIES OF AlSi10Mg ALLOY Maja Vončina, Stanislav Kores, Jožef Medved Faculty of Natural Science and Engineering, Department for Materials and Metallurgy, Aškerčeva 12, 1000 Ljubljana TOFA 2010 Discussion Meeting on Thermodynamics of Alloys, Porto, Portugal, September 2010

2 AIM The influence of Ce addition and cooling rate on the AlSi10Mg alloy was investigated using: equilibrium thermodynamic calculation, simple thermal analysis, differential scanning calorimetry, optical microscopy, scanning electron microscopy, tensile test and Brinell hardness The purpose is to study the variations that occur: at the solidification, at the precipitation and in the mechanical properties at different Ce additions and at different cooling rates.

3 EXPERIMENTAL Used experimental equipment and methods: Electric induction furnace ETA (simple thermal analyses) measuring cell made by Cronning process and measuring cell for controlled cooling DSC instrument (Jupiter 449c, NETZSCH) Optic microscope Olympus BX61 and Scanning electron microscope (SEM) SIRION 400nc, FEI Company equipped with the EDS analyzer INCA 350 Tensile test on Simulator of thermomechanical states GLEEBLE 1500D Brinell hardness test Electric induction furnace Measuring cell made by Cronning process STA 449c Jupiter, NETZSCH Gleeble 1500D Optic microscope Olympus BX 61 equipped with video camera and analysis 5.0 program Scanning Electron Microscope Sirion 400 NC

4 RESULTS and DISCUSSION-SIMULATION OF EQUILIBRIUM SOLIDIFICATION THERMO-CALC Temperature [ C] Mass percent Si [%] 1: Al 2 Cu θ 3: Mg 2 Si 5: Si 2 Ti 9: α Al 10: AlFeSi β 11: β Si 12: Al 6 Mn 13: AlMnSi α 14: Al 8 Ce 15: Liquid Isoplete equilibrium phase diagram of AlSi10Mg with 0.02 mass % Ce. L Si 2 Ti+L' L' α Al +L'' L'' Al 5 FeSi-β+L''' L''' AlMnSi-α+L'''' L'''' (α Al +β Si )+L''''' L''''' Al 8 Ce α Al Mg 2 Si α Al Al 2 Cu

5 1,0 86,0 10,5 α Al Mass pe ercent of phases [%] 0,8 0,6 0,4 0,2 β Si Mg 2 Si AlFeSi-β 85,5 85,0 84,5 Mass pe ercent of α Al [%] 10,4 10,3 10,2 10,1 Mass pe ercent of β Si [%] 0,0 Al 2 Cu-θ Si 2 Ti Al 8 Ce 0 0,01 0,02 0,05 mas.% Ce 84,0 10,0 Mass fraction of phases regarding the Ce addition in AlSi10Mg alloy. TOFA 2010, Discussion Meeting on Thermodynamics of Alloys, Porto, Portuugal, 12-17September 2010

6 RESULTS and DISCUSSION Temperature ( C) T L/min = 579,6 C T L/max = 581,5 C T E/min = 562,5 C T E/max = 566,5 C T E2 = 551 C T E3 = 547,5 C T S = 536,5 C -1, Time (s) Cooling curve and differential cooling curve of AlSi10Mg alloy 0,5 0,0-0,5 dt/dt ( C/s) T L/min - minimal liquidus temperature T L/max - maximal liquidus temperature T L r. - liquidus rekalescence T L p. - liquidus undercooling T E/min - minimal eutectic temperature T E/max - maximal eutectic temperature T E r. - eutectic rekalescence T E p. - eutectic undercooling T E2 - temperature of eutectic solidification (α Al +Mg 2 Si) T E3 - temperature of eutectic solidification (α Al +AlMgSiCu) T S - solidus temperature t strj. - time interval of the solidification: T L/min T S T L = 660, ,7 %Si + 4, %Fe + 3, %Mn - 2,5 %Mg T = 573, ,2 %Si + 3, E -11 %Fe - 2,5 %Mn - 5 %Mg

7 Temperature [ C] C/min 100 C/min Temperature ( C) AlSi10Mg AlSi10Mg+0,01 Ce AlSi10Mg+0,02 Ce AlSi10Mg+0,05 Ce AlSi10Mg+0,1 Ce C/min Time [s] Comparison of cooling curves of AlSi10Mg alloy at different cooling rates Time (s) Comparison of cooling curves of AlSi10Mg alloy with various Ce additions. Comparison of characteristic temperatures of solidification of AlSi10Mg alloy with various Ce additions.

8 RESULTS and DISCUSSION-DSC From the heating DSC curves it was determined: T p. - temperature of precipitation T E2 - temperature of eutectic melting (α Al +Mg 2 Si) T E - temperature of eutectic melting (α Al +β Si ) T L - temperature of melting α Al T Al5FeSi temperature of melting of Al 5 FeSi phase H p. - energy of precipitation H melt. - melting enthalpy From the cooling DSC curves of samples after thermal analysis it was determined : T L - temperature of solidification α Al T E - temperature of eutectic solidification (α Al +β Si ) T E2 temperature of eutectic solidification (α Al +Mg 2 Si) H sol. solidification enthalpy

9 Precipitation of Mg 2 Si phase at heating DSC curves Energy of the precipitation of Mg 2 Si precipitates

10 ( n ) f = 1 exp kt Deeply etched specimen from AlSi10Mg+0,02Ce Fraction of precipitation transformation at 0, 0.02 and 0.1 wt.% Ce is added.

11 ( n ) f = 1 exp kt Fraction of precipitation transforma ation [%] Deeply etched specimen from AlSi10Mg+0,02Ce Fraction of precipitation transformation regarding cooling rate

12 RESULTS and DISCUSSION-ETA + DSC Temperature of solidification of eutectic (α Al +Mg 2 Si)

13 RESULTS and DISCUSSION-OM AlSi10M g AlSi10Mg+0.01 Ce AlSi10Mg+0.02 Ce AlSi10Mg+0.05 Ce AlSi10Mg+0.1 Ce Microstructure of AlSi10Mg alloy with various Ce additions

14 RESULTS and DISCUSSION-SEM SEM micrograph of AlSi10Mg alloy with 0,02 mass % Ce Spectrum1: 42,23 at.% Al 38,57 at.% Si 4,13 at.% Mg 15,07 at.% Ce Spectrum 2: 48,76 at.% Al 21,11 at.% Si 30,13 at.% Mg Spectrum 3: 49,10 at.% Al 50,90 at.% Si Spectrum 4: 11,24 at.% Al 88,76 at.% Si Spectrum 5: 98,58 at.% Al 1,17 at.% Si 0,24 at.% Mg Spectrum 6: 98,63 at.% Al 1,21 at.% Si 0,16 at.% Mg

15 RESULTS and DISCUSSION-MECHANICAL PROPERTIRS Tensile strength of AlSi10Mg alloy with various Ce additions Brinell hardness of AlSi10Mg alloy TOFA 2010, Discussion Meeting on Thermodynamics of Alloys, Porto, Portuugal, 12-17September 2010

16 CONCLUSION Solidus temperature shifts to lower temperatures. When all cooling curves are compared it is evident that Ce extends the solidification interval when 0.01 and 0.02 wt.% Ce is added and shortens when 0.05 and 0.1 wt.% Ce is added. Mass fraction of Mg 2 Si slightly reduces with increasing Ce addition. Mass fraction of Al 8 Ce phase increases as the concentration of Ce increases. Data base COST2 and TTAl6 in Thermo- Calc program have some deficiency: they should be complemented with multicomponent phases with Ce. The solidification of eutectic (α Al +Mg 2 Si) shifts to lower temperature when Ce is added. Ce influences on the precipitation temperature and it is decreasing with the increasing concentration of Ce. The precipitation enthalpy also decreases with increasing Ce addition. When optimal concentration of Ce is added the precipitation takes course faster than at pure alloy and at alloy with 0.1 wt.% Ce. Optimal concentration of Ce in the alloy and higher cooling rate accelerates the precipitation kinetics. Rare earth metals such as Ce have been found to improve the mechanical properties of Al Si castings where they modify the microstructure and enhance the tensile strength and hardness when suitable concentration of Ce is added. Ce phase that forms in AlSi10Mg alloy is AlSiCe phase of roundish poliedric shape.

17 Thank You for Your attention!