“Influence of Si, Sb and Sr Additions on the Microstructure ...

More documents

Recommendations

Info

Chapter 4: Results <strong>and</strong> Discussion <strong>and</strong> Mg17Al12 as explained earlier. The SEM photograph <strong>of</strong> cross section near the fracture surface <strong>of</strong> creep ruptured AZ9l+0.5<strong>Si</strong> alloy is shown in Figure 4.67, it could be seen that many cracks are initiated from the massive as well as discontinuous precipitate <strong>of</strong> Mg|7Al|2 <strong>and</strong> spreads throughout the matrix. These cracks are obstructed by the Mg2<strong>Si</strong> precipitates at the grain boundary. However, cavity formation <strong>and</strong> cracking at these intermetallics (Mg2<strong>Si</strong> <strong>and</strong> Mg3<strong>Sb</strong>;) is the s<strong>of</strong>tening mechanism, which leads to the final fracture at last. Cracks <strong>and</strong> cavities at both Mg;<strong>Si</strong> <strong>and</strong> Mg3<strong>Sb</strong>; intermetallics are also seen in the crept microstructure <strong>of</strong> <strong>Si</strong> <strong>and</strong> <strong>Sb</strong> added alloys (see Figures 4.66 & 4.67). However, the interrupted microstructure <strong>of</strong> AZ9l+0.5% <strong>Sb</strong> added alloy creep tested up to 6000 h at 150°C shown in Figure 4.68, indicate that the Mg;<strong>Sb</strong>; intermetallic is intact. This gives rise to an extended secondary creep region. Hence, the final failure is decided by the intermetallics as how long it prevents the crack propagation. ln the present study, it is also found that both the morphologies (Chinese script <strong>and</strong> polygonal) <strong>of</strong> Mg;<strong>Si</strong> intermetallic exhibits similar creep properties, despite the tensile properties are sensitive with the morphology, which indicates that the Chinese script does not affect the creep properties. Recently, Dargush et al. [318] also reported that the morphology <strong>of</strong> the Chinese script Mg;;<strong>Si</strong> is effective to hold the grain boundary against sliding during creep. As shown in Figure 2c, it has multiple arms extended into neighboring grains thereby restrict the grain boundary movement effectively. Another possible explanation is the difference in type <strong>of</strong> load applied during tensile <strong>and</strong> creep testing. The normal strain rate used for tensile testing is much higher (103 to 104 S4) than the strain rate encountered during creep testing (in the range <strong>of</strong> 10'? S"). At higher strain rate, accumulation <strong>of</strong> dislocations at the interface <strong>of</strong> matrix <strong>and</strong> hard intermetallic is at a faster rate, which increases the local stress level <strong>and</strong> leads to cracking. On the other h<strong>and</strong>, dislocation pile up is at slower rate during creep <strong>and</strong> hence strengthening effect due to its multiple arm morphology, as it restricts the grain boundary movement, dominates. Due to this, the creep behavior <strong>of</strong> AZ91 improves by the presence <strong>of</strong> massive size Mg2<strong>Si</strong> with Chinese script morphology even though it reduces tensile properties. 158
Chapter 4: Results <strong>and</strong> Discussion Figure 4.66: Continuous precipitates occurred around the intermetallics during creep at 150°C (a) AZ9l (b) AZ91+0.5% <strong>Si</strong> (c) AZ91+0.5% <strong>Sb</strong> 159 i
Page 1 and 2:
iié»a'5 INFLUENCE OF Si</
Page 3 and 4:
DECLARATION I hereby declare that t
Page 5 and 6:
_ _ Acknowledgements I am very much
Page 7 and 8:
ABSTRACT _ Abstract The use <strong
Page 9 and 10:
A Abstract The microstructure <stro
Page 11 and 12:
_ _ 1 Abstract intermetallic are al
Page 13 and 14:
2.7.2 Page No Zirconium Free Alloys
Page 15 and 16:
Page No 3.4.4 Hardness ------------
Page 17 and 18:
J 1 1 J N0 No LIST OF TABLES Table
Page 19 and 20:
LIST OF FIGURES Figure . Page l N0.
Page 21 and 22:
5 3.7 it . — 7 ‘ 7 ———
Page 23 and 24:
; Intermetallic ‘ 4.23 Microstruc
Page 25 and 26:
at 200°C 4.59 Creep curves <strong
Page 27 and 28:
1.1 MAGNESIUM lllllI"l'IlI 1: IIITI
Page 29 and 30:
H Chapter 1: Introduction AZ9l allo
Page 31 and 32:
_ Chapter 1: Introduction In summar
Page 33 and 34:
Chapter 1: Introduction choice for
Page 35 and 36:
60 -. 50 _..z I 1' %1 ' Passen
Page 37 and 38:
qChapter 2: Literature Review Table
Page 39 and 40:
Chapter 2: Literature Review 5¢l¢
Page 41 and 42:
M Chapter 2: Literature Review to s
Page 43 and 44:
T Chapter 2: Literature Review effi
Page 45 and 46:
_ g _ Chapter 2:Literature Review V
Page 47 and 48:
_ Chapter 2: Literature Review pres
Page 49 and 50:
Chapter 2: Literature Review solidi
Page 51 and 52:
; l It L .r . _ 1 Chapter L2: Liter
Page 53 and 54:
-- ChaPt°l-2LLil°'3t"'° Review m
Page 55 and 56:
H _ g Chapter2: Literature Review p
Page 57 and 58:
2.8.4 Heat Treatment 2.8.4.1 Genera
Page 59 and 60:
Chapter 2: Literature Review report
Page 61 and 62:
_ _ _ Chapter 2: Literature Review
Page 63 and 64:
Chapter 2: Literature Review *1" m
Page 65 and 66:
_p g Chapter 2: Literature Review w
Page 67 and 68:
Chapter 2: Literature Review fractu
Page 69 and 70:
_ Chapter 2: Literature Review On t
Page 71 and 72:
Ii | ‘I I Chapter U 2: Literature
Page 73 and 74:
_ _ W pp Chapter 2: LiteratureRevie
Page 75 and 76:
_ _WChapter 2: Literature Review Th
Page 77 and 78:
1 _ Chapter 2W:Litegrature Review R
Page 79 and 80:
_ Chapter 2: Literature Review, to
Page 81 and 82:
Chapter 2: Literature Review increa
Page 83 and 84:
_ H Chapter 2: Literature Review bi
Page 85 and 86:
2.9.5 Strontium _- ChaPl°F..2.?_i:
Page 87 and 88:
2.11 SCOPE OF THE WORK Chapter 2: L
Page 89 and 90:
l}llll"l'IlI 3: lll'l'IlIl|llS llll
Page 91 and 92:
Chapter 3: Materials and</s
Page 93:
Chapter 3: Materials and</s
Page 96 and 97:
f W _ _ Chapter 3g:lVlaterials <str
Page 98 and 99:
3.6 X-RAY DIFFRACTION (XRD) Chapter
Page 100 and 101:
_ Chapter 3: Materials and<
Page 102 and 103:
_ _ Chapter 3: Materials an
Page 104 and 105:
BIIIFIEII ll: IISBITS llll IIISIBII
Page 106 and 107:
Chapter 4: Results and</str
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
L Chapter 4; Results and</s
Page 114 and 115:
ll Ii l I A Chapter 4: Results <s
Page 116 and 117:
_ pg Chapter 4: Results and
Page 118 and 119:
Page 120 and 121:
_ _ _ _ _ Chapter 4: Results <stron
Page 122 and 123:
T 1 H Cghapter4: Results an
Page 124 and 125:
I. Chapter 4: Results and</
Page 128 and 129:
i. i l _ _ g Chapter 4: Results <st
Page 130 and 131:
_ H Chapter 4: Results and<
Page 132 and 133: Chapter 4: Results and</str
Page 134 and 135: g Chapter 4; Results and</s
Page 138 and 139: _ _g Chapter 4:Results and<
Page 140 and 141: ii A r I {I i L 1 x Chapter 4: Resu
Page 144 and 145: _ Chapter 4: Results and</s
Page 146 and 147: _ pg Chapter 4: Results and
Page 148 and 149: 250 Chapter J4: Results and
Page 154 and 155: 250 ZN 0 Chapter 4: Results <
Page 158 and 159: H Kg Chapter 4: Results and
Page 162 and 163: 4.5 CREEP BEHAIVOR i g Chapter 4: R
Page 168 and 169: 0.9 - ‘_ g o.a - ' AZ91 i - I AZ9
Page 170 and 171: 1.0- e 4| 1 - AZ91 I 08- * - AZ91+0
Page 172: _ _ u Chapter 4; Results an
Page 177 and 178: 4.5.7 Post Creep Microstructural An
Page 181: g Chapter 4: Results and</s
Page 185 and 186: W Chapter 4: Results and</s
Page 191 and 192: _ _ K Chapter 4; Results an
Page 195 and 196: K Chapter 4: Results and</s
Page 197 and 198: IBIIIFIEII 5: IBIIIIBIISIIIIS In th
Page 199 and 200: Chapter 5: Conclusions However, the
Page 201 and 202: 3. 4. Chapter 5: Conclusions found
Page 203 and 204: l. 2. 3. 4. 5. 6. 7. 8. 9. l0 ll 12
Page 205 and 206: E References W. Blum, B. Watzinger
Page 207 and 208: __ _ References M. O. Pekguleyuz: M
Page 209 and 210: References 97.0. Lunder, T. Kr. Aun
Page 211 and 212: References l32.M.T. Perez-Prado, J
Page 213 and 214: _ _ _ References l70.A. Alahelisten
Page 215 and 216: References 204.M. R. Bothwell, H. P
Page 217 and 218: _ References 240.Smithells Light Me
Page 219 and 220: References 278. P. Zhang, B. Watzin
Page 221 and 222: References 31 l.Metal Hand<
Page 223 and 224: Nat1on_al/International Conference
Page 225: Page 125: Para 1 7 Explained to the
show all

“Influence of Si, Sb and Sr Additions on the Microstructure ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?