dissertation global and local fracture properties of metal matrix ...

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(1.) aging at 175°C for 15min; (2.) aging at 175°C for 8h; (3.) aging at 175°C for24h; (4.) aging at 175°C for 200h. Section 4 Fig. 4.6. The microstructure of the Al6061-10%SiC. Analogously to the cast MMCs, the investigated specimens of the PM MMC are referred to by the volume percentage and the heat treatment, e.g., Specimen SiC-10-15min., Specimen SiC-10-8h, etc. 4.1.2.2. Compression tests Because of the low ductility of these materials, the compression tests are used to determine the mechanical properties. The difficulty is the prevention of buckling, which is avoided by the use of small gauge length / gauge diameter ratios (2 - 3) [2]. The compression test specimens have a standard cylindrical shape with a diameter of 8 mm and a length of 20 mm. The compression tests are conducted on the mechanical testing machine “ZWICK” at a loading rate 5.6·10 -4 s -1 . No buckling of the tested specimens is observed. The strain hardening coefficient, N, and the coefficient, α, are determined as in the case of the cast MMCs. The results of the compression tests are collected in Table 4.3. 35 200 µm
Section 4 Table 4.3. Mechanical properties of the PM-MMC Al6061-10%SiC determined by compression tests. It should be noted that tensile tests were performed, as well. In Figure 4.7, the true stress- strain curves for Specimen SiC-10-15min determined by compression and tensile tests are given. It is seen that these curves coincides. But since the tensile specimen fails at very low fracture strain, the N- and α-values cannot be determined from the tensile true stress-strain curve. Material Stress [MPa] 500 400 300 200 100 0 E [Gpa] σy [MPa] σUTS [MPa] 0 5 10 15 20 25 Strain [%] N α SiC-0-15min 71 197 380 0.27 5.22 7.1 SiC-0-8h 71 340 474 0.09 0.99 2.9 SiC-0-24h 71 315 434 0.08 0.95 1.2 SiC-0-200h 71 232 333 0.09 1.07 1.9 36 compression tension power-law Fig. 4.7. The true stress-strain curves for Specimen SiC-10-15min. Ji [kN/m] Jic (HR) [kN/m] SiC-10-15min 88 210 420 0.21 2.94 5.5 11.9 3.4 SiC-10-8h 88 360 470 0.09 1.43 3.6 20.4 4.0 SiC-10-24h 88 348 440 0.08 2.04 2.9 19.8 3.8 SiC-10-200h 88 295 375 0.09 2.02 3.9 16.8 3.4 Jic (P) [kN/m]
Page 1 and 2: MONTANUNIVERSITÄT MONTANUNIVERSIT
Page 3 and 4: TABLE OF CONTENTS 1. Introduction 5
Page 5 and 6: 7.4.4. The effect of ECAP on the lo
Page 7 and 8: Section 1 The main results of this
Page 9 and 10: Section 2 2.2. The influence of the
Page 11 and 12: Section 2 high strength, fine reinf
Page 13 and 14: Section 2 etched to mark the inclus
Page 15 and 16: Section 2 (4.) The specimen prepara
Page 17 and 18: Section 3 Fig. 3.1. The digital ele
Page 19 and 20: height [µm] height [µm] 10 0 -10
Page 21 and 22: Section 3 Fig. 3.5. The observation
Page 23 and 24: Section 3 3.3.2. The determination
Page 25 and 26: Section 3 The Eshelby tensor does n
Page 27 and 28: equivalent stress Section 3 Fig. 3.
Page 29 and 30: Assume σ m eq Calculate matrix sec
Page 31 and 32: Section 4 Table 4.1. Chemical compo
Page 33 and 34: 4.1.1.3. Fracture mechanics tests S
Page 35: Section 4 Fig. 4.4. A view of a com
Page 39 and 40: εfr [%] εfr [%] N 16 12 8 4 0 150
Page 41 and 42: Section 4 4.2. The effect of the he
Page 43 and 44: Section 4 It should be noted that n
Page 45 and 46: CODi [µm] 40 30 20 10 0 Section 4
Page 47 and 48: Section 4 Table 4.4. Results of the
Page 49 and 50: CODi [µm] COD i [µm] CODi [µm] 2
Page 51 and 52: Cast MMCs 10%-RT 10%-8h 10%-24h 10%
Page 53 and 54: COD vi [µm] COD vi [µm] CODvi [µ
Page 55 and 56: CODvi [µm] CODvi [µm] 80 60 40 20
Page 57 and 58: Section 4 Table 4.6. The values of
Page 59 and 60: σ p max [MPa] σ p max [MPa] σ p
Page 61 and 62: σ p max [MPa] σ p max [MPa] 1200
Page 63 and 64: σ interf max [MPa] σ interf max [
Page 65 and 66: Section 4 4.5. The relation between
Page 67 and 68: Section 4 Table 4.9. Conditions for
Page 69 and 70: Ln(Ln(1/(1-F σ))) Ln(Ln(1/(1-F σ)
Page 71 and 72: Section 5 diameter of 2…8 µm and
Page 73 and 74: MnS-inclusion r θ MnS-inclusion Se
Page 75 and 76: σ interf [MPa] σ interf [MPa] σ
Page 77 and 78: Section 6 where n is the number of
Page 79 and 80: Ji [kN/m] J i [kN/m] 25 20 15 10 5
Page 81 and 82: Section 7 7.2. A model by Tan and Z
Page 83 and 84: Section 7 its initial length, li. O
Page 85 and 86: 1 µm Section 7 5 µm Fig. 7.3. A s
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Section 7 a) b) c) Fig. 7.4. Micros
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Section 7 It is important that no p
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Section 7 between the Rtot and the
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Section 7 Fig. 7.8. The fracture su
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10 z [mm] 5 -10 -15 Section 7 0 -20
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Section 7 Table 7.3. Data on measur
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8. Summary Section 8 This work deal
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Section 8 The effect of the homogen
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Table 9.1. Data on stress for Speci
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Table 9.11. Data on stress for Spec
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Table 9.17. Results of the stereoph
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1 2 1 2 3 3 4 5 6 5 9 119 7 7 8 9 6
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8 9 10 6 10 122 11 12 13 14 11 12 1
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9 10 11 12 13 124 50 µm Fig. 9.6.
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1 2 1 2 3 3 4 4 126 5 5 6 9 7 50 µ
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1 1 2 2 3 4 3 4 5 5 128 6 7 6 7 50
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Fig. 9.12. Fracture surface with ma
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1 2 3 1 2 3 4 5 6 7 8 9 10 4 5 132
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Fig. 12.36. Fracture surface of the
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[14] Lewandowski JJ, Liu C, Hunt WH
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[42] Rice JR, Rosengren GF. Plane s
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[70] ASTM E1820-01, “Standard Tes
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