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CONTENTS
Subject Page No.
Title Page i
Certificate of Approval iii
Certificate v
Declaration vii Acknowledgements ix List of Symbols xi List of Abbreviations xiii Abstract xv Contents xvii Chapter 1 Introduction………... 1
Chapter 2 Literature review……….. 5
2.1 Introduction………... 5
2.2 Review of solidification………...6
2.2.1 Cast microstructure…..………...6
2.2.2 Solidification rate………...6
2.2.3 Casting processes………...7
2.3 Grain refining of aluminium alloy……….... 8
2.4 Review of Aluminium-Scandium alloy……….11
2.4.1 Binary Al-Sc alloy……….…...11
2.4.2 Ternary Al-Sc-Zr alloy………...12 xvii
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2.4.3 Quaternary Al-Mg-Sc-Zr alloy……….. 14
2.4.4 Other alloying addition to the Al-Sc alloy……….15
2.4.5 Age hardening behavior of Al-Sc alloy…………..16
2.4.6 Mechanical properties of Al-Sc alloy…………...17
2.4.7 Wear behavior of Al-Sc alloy………20
2.4.8 Corrosion behavior of Al-Sc alloy………. 20
2.5 Metal Matrix Composite………. 22
2.5.1 Preparation of particulate composite………. 22
2.5.2 Mechanical properties of composite………...25
2.5.3 Wear behavior of composite………...26
2.5.4 Corrosion behavior of composite………... 26
Chapter 3 Experimental procedure………... 29
3.1 Introduction………... 29
3.2 Selection of materials……… 29
3.3 Preparation of alloys and composites……… 31
3.3.1 Preparation of alloys……….. 34
3.3.2 Preparation of composites……….. 34
3.4 Chemical analysis………..37
3.5 Metallography………... 39
3.5.1 Optical microscopy……….39
3.5.2 Scanning Electron Microscopy……….. 39
3.5.3 Transmission Electron Microscopy…………..…. 40
3.6 Cold and hot rolling……….. 40
3.7 Heat treatment………... 41
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3.8 Mechanical properties………... 41
3.8.1 Hardness measurement………..………. 41
3.8.2 Tensile test……….………. 42
3.9 Wear test………... 42
3.10 Physical properties……….……….. 43
3.10.1 Density measurement………... 43
3.10.2 X-ray diffraction studies……… 43
3.10.3 Electrical resistivity measurement………...43
3.10.4 Differential Thermal Analysis (DTA)………... 44
3.11 Corrosion test………... 44
Chapter 4 Results and discussion……….. 45
4.1 Introduction……….. 45
4.2 Casting characteristics……….. 45
4.3 Microstructure………. 48
4.3.1 Result of Binary Al-Sc alloys………..……… 48
4.3.1.1 As-cast………..…………48
4.3.1.1 As-cast ageing……….………. 55
4.3.2 Discussion of the binary Al-Sc alloys……….…………55
4.3.3 The addition of Zr to the binary Al-Sc alloys………...59
4.3.3.1 As-cast………..59
4.3.3.2 As-cast ageing………. 61
4.3.4 Discussion of the addition of Zr to the binary Al-Sc alloys………...66
4.3.5 Results of ternary Al-0.3Sc-0.15Zr alloy…………...67
4.3.5.1 As-cast………. 67
4.3.5.2 As-cast ageing……….……. 74
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4.3.6 Discussion from the ternary
Al-0.3Sc-0.15Zr alloy………...77
4.3.7 The addition of Mg to the ternary Al-0.3Sc-0.15Zr alloy………81
4.3.7.1 As-cast……… 81
4.3.7.2 As-cast ageing……… 85
4.4.8 Discussion of the addition of Mg to the ternary Al- 0.3Sc-0.15Zr alloy..………...87
4.3.9 The addition of TiB2 and Mg to the ternary Al-0.3Sc0.15Zr alloy………...93
4.3.9.1 As-cast……… 93
4.3.9.2 As-cast ageing………. 101
4.3.10 Discussion of the addition of TiB2 and Mg………...103
4.4 X-ray diffraction analysis………... 107
4.5 Density variation………... 111
4.6 Electrical resitivity measurement ………... 118
4.7 Differential Thermal Analysis (DTA)………... 118
4.8 Hardness……… 122
4.8.1 Binary Al-Sc and ternary Al-Sc-Zr alloys………122
4.8.2 Ternary Al-0.3Sc-0.15Zr………... 124
4.8.3 Addition of Mg to the ternary alloy………...127
4.8.4 Addition of (TiB2)p and Mg to the ternary alloy... 131
4.8.5 Hot and cold rolling………..131
4.9 Tensile properties………. 141
4.9.1 Addition of Mg and the variation in cooling rate………. 141
4.9.2 Addition of Mg and TiB2 to the ternary alloys……….142
4.10 Wear properties……… 148
4.10.1 Addition of Mg and the variation in cooling rate………...148
4.10.2 Addition of Mg and (TiB2)p to the ternary Al-0.3Sc-0.15Zr………...153
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4.11 Corrosion………. 160
4.11.1 The addition of Mg to the ternary alloys………... 160
4.11.2 The addition of (TiB2)p and Mg……….…...164
Chapter 5 Conclusions……….….169
Chapter 6 Summery and view……….……….173
REFERENCES………175 Curriculum vita
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LIST OF TABLE CAPTIONS
Table Page No.
2.1 Tensile properties of Al alloys with Sc……… ….19
2.2 Tensile properties of particulate reinforced Aluminium alloy composite... ….25
3.1 Instantaneous cooling rate (0C/s) obtained in different moulds...….37
3.2 Chemical compositions of Al-Sc and Al-Sc-Zr alloys (wt %)……….….38
3.3 Chemical compositions of the Al-Sc-Zr, Al-Mg and Al-Mg-Sc-Zr alloys (wt %)………...….38
3.4 Chemical compositions of composites (wt %)……….….38
3.5 List of wear parameters used………... ….42
4.1 Results of the local EDX analysis performed on sand-cast binary Al- 0.05Sc, Al-0.1Sc and Al-0.5Sc alloys. Composirions are in at%...….54
4.2 Results of the local EDX analysis performed on sand-cast ternary Al- 0.5Sc-Zr alloy. Compositions are in at %...….61
4.3 Results of the local EDX analysis performed on CD cast sample. Compositions are in at. %...….67
4.4 Results of the local EDX analysis performed on CD cast sample. Compositions are in at. %...….72
4.5 EDX micro-chemical analysis (in at %) of the corresponding point in figure 4a………...….101
4.6 Resistivity of the as-cast and aged Al-6Mg-0.3Sc-0.15Zr alloy...….118
4.7 Solidus and liquidus temperature of the different alloy ….………. ….119
4.8 Strength properties of the Al-6Mg-0.3Sc-0.15Zr alloy...….141
4.9 Strength properties of the Al-xMg-0.3Sc-0.15Zr alloy reinforced with 5wt% (TiB2)p composites cast in QIC...….142
4.10 Summary of the results of polarization resistance measurement of different alloys in 3.56 wt% NaCl solution………..….161
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4.11 Corrosion rate by weight loss technique of the different alloy in HCl,
H2SO4 and NaCl solution……….….164 4.12 Summary of results of polarization resistance measurement of different
composites in 3.56 wt% NaCl………..….165 4.13 Corrosion rate by weight loss technique of the different alloy in HCl,
H2SO4 and NaCl solution……….….167
LIST OF FIGURE CAPTIONS
Figure Page No.
2.1 Al-rich end of the binary Al-Sc equilibrium phase diagram...…..12 2.2 Isothermal section of Al corner of the ternary Al-Sc-Zr phase diagram
at 6000C……….…..13
2.3 Isothermal section of Al corner of the ternary Al-Mg-Sc phase diagram
at 4300C……….…..14
3.1 Photographs of different moulds used for obtaining wide range of cooling rates and their schematic diagrams………..…..33 3.2 Schematic diagram of the experimental set-up of oil quenching………..…...33 3.3 Samples cast in (a) sand mould, (b) alumina insulated mould, (c)
copper die, (d) QIC (marked 1) and CIC (marked 2). (e) A cross section of the wedged shape casting………. …..35 3.4 Cooling curve of sand cast (a) binary Al-Sc and (b) ternary Al-Sc-Zr
alloys and (c) quaternary Al-6Mg-0.3Sc-0.15Zr alloy cast in QIC and
CIC process………...…..37
3.5 Schematic diagram of the tensile specimen.……….…..42 4.1 Samples cast in (a) investment shell mould showing defects during oil
quenching and (b) surface shrinkage in a component. Hot crack surface of the sample cast in (c) oil quenching investment casting and (d) Cu-
die casting……….…..47
4.2 Optical micrograph of the as-cast (a) Al-0.05Sc (b) Al-0.1Sc and (c) Al0.5 Sc alloys cast in RSM……….…..49
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4.3 Optical micrograph etched with Keller’s agent of the as-cast (a) Al- 0.05Sc (b) Al-0.1Sc and (c) Al-0.5Sc alloys cast in RSM showing the grain boundary precipitates……….. …..51 4.4 SEM micrographs of the samples cast in RSM. The as-cast (a)
Al0.05Sc alloy showing the coarse Si particles precipitates at the interdendritic region, Al 0.1Sc alloy (b) low magnification, (c) enlarged micrograph (a) of the region marked 1 and Al 0.5Sc alloy showing the pure (d) Al3Sc precipitates marked D and Fe rich phase marked by
arrow..………...…..53
4.5 TEM micrograph of as-cast (a) Al0.5Sc alloy cast in RSM showing many dispersive precipitates in the matrix………..54 4.6 Annealed (at 4700C for 24 hours) microstructure of Al0.05Sc alloy cast
in RSM (a) showing Al3Sc precipitates and dislocation line interaction and (b) dislocation density. (c) Dense dislocation line and (d) at a higher magnification non-coherent particle in Al-0.1Sc alloy cast in
RSM………..…..57
4.7 Optical micrograph of the as-cast (a) Al-0.05Sc-0.15Zr (b) Al-0.1Sc- 0.15Zr and (c) Al-0.5Sc-0.15Zr alloys cast in RSM……….…..61 4.8 SEM micrograph of as-cast (a) Al-0.05Sc-0.15Zr alloy cast in RSM
showing typical precipitates at the interdendritic region, (b) enlarged micrograph (a) of the region marked 1, (c) Al-0.5Sc0.15Zr alloy cast in RSM low magnification micrograph and (d) high magnification of the primary particles ……… …...…..63 4.9 TEM micrographs of the alloys cast in RSM and annealed at 4700C for
24 hours. Annealed microstructure of (a) Al-0.05Sc-0.15Zr alloy is showing dense dislocation line interaction, semi coherent particle in (b) Al-0.1Sc-0.15Zr and (c) Al-0.5Sc-0.15Zr alloys and (d) precipitates density in Al-0.5Sc-0.15Zr alloy...…..65 4.10 Optical micrograph showing the grain structure of the sample cast in (a)
Cu Die and (b) alumina insulated mould. SEM micrograph of the as- cast precipitates in Cu-die (c) low magnification and (d) enlarge micrograph (c) of the region marked by A... …..69 4.11 SEM micrographs of the Al-0.3Sc-0.15Zr cast in AIM showing the (a)
faceted Al3 (Sc, Zr) particle, (b) a typical fan shaped precipitate, (c) low magnification of the grain boundary and (d) enlarge micrograph (c) of the region marked by B...
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4.12 TEM micrographs of the Al-0.3Sc-0.15Zr alloy cast in AIM showing the precipitates (a) originated from the grain boundary, (b) dense and (c) less precipitate...…..73 4.13 TEM micrograph of Al-0.3Sc-0.15Zr alloy cast in CD showing the
precipitates in (a) as-cast (b) aged at 300 0C for 2h and (c) 400 0C for 2h sample...…..75 4.14 TEM micrograph of copper die cast sample aged at 4000C for 2 hours
showing the (a) coherent and coexisting of coherent and semi coherent precipitates in (b) copper die and (c) AIM cast sample...…..77 4.15 Optical micrograph of Al-6Mg-0.3Sc-0.15Zr as-cast alloy cast in QIC
and etched with Keller’s reagent (a) showing the refined grain structure with duplex grain size distribution, electrolytic polished and without etched sample cast in CIC at (b) lower magnification. Optical micrograph of as-cast CIC showing (c) coarse precipitates inside the grain and (d) enlarge micrograph of the coarse precipitate...…..83 4.16 SEM micrograph of Al-6Mg-0.3Sc-0.15Zr as-cast QIC alloy (a) star
like Al3(Sc, Zr) primary particle with very small precipitates of Al3Sc at and around the primary particle, (b) small different round size precipitates of Al3Sc inside the grain and (c) line scan of the primary precipitates along the line BB of (a)...…..85 4.17 Optical micrographs of Al-6Mg-0.3Sc-0.15Zr alloy electrolytic
polished and without etch QIC sample (a) as-cast- aged at 3000C for 5 hours and (b) 4000C for 1 hour...…..86 4.18 TEM micrograph of Al-6Mg-0.3Sc-0.15Zr alloy aged at 3000C for 4
hours of (a) CIC and (b) QIC processed alloy and (c) EDP of the fine precipitate corresponding (b)……… …...…..89 4.19 Optical micrographs of as-cast composites etched with Keller’s reagent
of (a) 0Mg, (b) 1.5 Mg, (c) 3.5Mg and (d) 6 Mg cast in QIC...…..95 4.20 Variation in grain size of the samples cast in QIC with increase in Mg
content...…..96 4.21 As-cast unetched SEM micrograph of the (a) & (b) 0 Mg, (c) & (d)
1.5Mg, (e) & (f) 3.5Mg, (g) & (h) 6Mg composites cast in QIC and (i)
EDX line scan analysis along AA of (c)...…..100
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4.22 Bright field image TEM micrograph of the composite with 3.5% Mg composite cast in QIC showing (a) a cell structure precipitation of TiB2, (b) the dense and uniform distribution of the TiB2 particles and (c) the fine precipitates of Al3Sc, Al3(Sc, Zr) in the corresponding dark field image of (b) aged at 3000C for 5 hrs...…..103 4.23 As-cast SEM micrograph of 3.5Mg composite cast in QIC showing
primary particles inside the grain by arrows……….…..105 4.24 As-cast (a) optical micrograph and (b) SEM micrograph of 3.5Mg
composite cast in AIM showing primary coarse grain structure and
coarse TiB2 particles………. …..106 4.25 XRD of the as-cast binary Al-2Sc, Al-0.5Sc and ternary Al-0.5Sc-
0.15Zr alloys cast in RSM……….…..107 4.26 X-ray diffraction taken from the as-cast Al-6Mg-0.3Sc-0.15Zr alloy
cast in QIC and NIC and as-cast Al-0.3Sc-0.15Zr sample cast in QIC....…..109 4.27 X-ray diffraction taken from the as-cast 0, 1.5, 3.5 and 6 Mg composite
samples cast in QIC...…..110 4.28 Density variation (a) along the height and (b) transverse direction of the
Al-6Mg-0.3Sc-0.15Zr alloy cast in QIC and CIC………. …..112 4.29 Microstructure at the (a) highest density and (b) lowest density region
of the QIC sample, (c) and (d) frequently observed pores in CIC
sample………...…..114
4.30 Simulation result of the aluminium alloy showing the temperature
profile of (a) CIC and (b) QIC………..…..116 4.31 Density variation with the % increase in rolling of (a) Al-6.0Mg-0.3Sc-
0.15Zr alloy (b) 3.5 Mg composite………... …..117 4.32 DTA curves of (a) Al-0.3Sc-0.15Zr, (b) Al-6Mg-0.3Sc-0.15Zr, (c) Al-
4.5Mg alloys and (d) Al-3.5Mg-0.3Sc-0.15Zr / (TiB2) composite cast in
QIC……… ………...…..121
4.33 Hardness variation with increase in Sc of the binary and ternary samples cast in RSM……….…..122
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4.34 Hardness variation of the ternary alloy cast in different mould during ageing at (a) 300 0C with time and (b) at 150, 300, 400, 500 and 600 0C for 2 hours...…..125 4.35 Percentage increase in hardness on ageing compared to as-cast hardness
of Al-6Mg-0.3Sc-0.15Zr alloy cast in CIC and QIC (a) at 3000C and (b) softening curve at 4000C with time……….. .... …..129 4.36 Sketch of the (a) wedge shape cast sample is showing the variation in
hardness (b) along the length and (c) transverse section of the Al-6Mg-
0.3Sc-0.15Zr alloy cast in QIC……….…..129 4.37 Hardness variation of the composite samples with different Mg
concentration cast in QIC during isothermal ageing at the temperature of (a) 3000C (b) 4000C and (c) as-cast, peak age and retained hardness
at 4000C……….…..133
4.38 Sketch of the (a) wedge shaped cast sample is showing the variation in hardness (b) along the length and (c) transverse section of Al-3.5Mg-
0.3Sc-0.15Zr/ (TiB2)p composite cast in QIC………..…….…..133 4.39 The variation in hardness in lateral direction at 10, 20, 30 and 40%
reduction in cold rolling of (a) as-rolled and ageing at 3000C of Al-
6.0Mg- 0.3Sc 0.15Zr alloy cast in (b) CIC and (c) QIC……….….. …..135 4.40 The hardness variation in lateral direction on ageing at 3000C of the Al-
6Mg-0.3Sc-0.15Zr alloy rolled at room temperature (RT), 150 and
2500C. The samples cast in (a) CIC and (b) QIC……….…..137 4.41 The variation in hardness at the lateral direction of 10, 20, 30 and 40%
reduction in cold rolling of (a) as-rolled and ageing at 3000C of Al-
3.5Mg- 0.3Sc 0.15Zr / (TiB2)pcomposite cast in (b) CIC and (c) QIC… …..139 4.42 The hardness variation in lateral direction on ageing at 3000C of the Al-
3.5Mg-0.3Sc-0.15Zr / (TiB2)p composite rolled at room temperature (RT), 150 and 2500C. The samples cast in (a) CIC and (b) QIC……….…..140 4.43 Fractograph of the peak aged Al-6Mg-0.3Sc-0.15Zr alloy cast in (a)
CIC (b) QIC... ....…..144 4.44 Fractograph of the peak aged (a) 0 Mg, (b) 1.5 Mg, (c) and (d) 3.5Mg
and (e) & (f) 6 Mg composite cast in QIC...…..147
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4.45 The changes in (a) and (d) wear rate and (b) and (c) with distance of travel and increase in load respectively of Al-6Mg-0.3-Sc-0.15Zr alloy.
The variation in (e) Co-efficient of friction is shown with increase in sliding distance of Al-6Mg-0.3-Sc-0.15Zr alloy...…..151 4.46 Worn out surface of peak aged Al-6Mg-0.3-Sc-0.15Zr alloy cast in (a)
CIC (b) QIC...…..152 4.47 With the increase in travel distance the variation in the (a) wear rate
and (c) the cumulative volume loss (e) coefficient of friction of the composites cast in QIC. Increase in load the variation in the (b) wear
rate and (d) the cumulative volume loss of the composites cast in QIC...…..155 4.48 Worn out surface of peak aged sample of (a) 0Mg (b) 1.5 Mg, (c) and
(d) 3.5Mg and (d) and (e) 6.0 Mg composites cast in QIC...…..159 4.49 Influence of Mg on the polarization behavior of Al-0.3Sc-0.15Zr alloy
in 3.5 wt% NaCl solution………. …..161 4.50 SEM micrograph of corroded surface of (a) 4.5Mg (b) 4.5Mg-0.3Sc-
0.15Zr and (c) 6.0Mg-0.3Sc-0.15Zr alloy cast in QIC after immersion in 3.5 wt% NaCl solution for 6 hours………...…. …..163 4.51 Influence of Mg on the polarization behavior of TiB2 reinforced
composite in 3.5 wt% NaCl solution cast in QIC………... …..165 4.52 SEM micrograph of corroded surface of Al-3.5Mg-0.3Sc-0.15Zr
/(TiB2)p composite cast in QIC after immersion in 3.5 wt% NaCl
solution for (a) 6 (b) 24 and (c) 840 hours……….. .…..167
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