Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
4 Table of contents
IV.4.3.1 Procedure .............................................................................................................. 114
IV.4.3.2 Calculation of the local strain components ........................................................... 115
IV.4.3.3 Computation of the in-plane components of the logarithmic strain tensor ............ 117
IV.4.3.4 Per-phase average strains .................................................................................... 118
IV.4.3.5 Errors on the computation of the strains ............................................................... 118
IV.5 Comparison between D1 and D2 Widmanstätten microstructures .... 119
IV.5.1 Results ........................................................................................................ 119
IV.5.1.1 Macroscopic stress-strain curves .......................................................................... 119
IV.5.1.2 Micro-scale strain analysis .................................................................................... 120
IV.5.2 Discussion ................................................................................................... 129
IV.5.2.1 What is the origin of the difference between D2_W and D1_W in terms of strain
partitioning? ............................................................................................................................ 129
IV.5.2.2 Why is the overall strain different from the macroscopic strain? .......................... 132
IV.5.3 Conclusions................................................................................................. 135
IV.6 Factors potentially impacting strain localization ................................ 135
IV.6.1 Influence of the temperature ........................................................................ 135
IV.6.1.1 Equiaxed morphology ........................................................................................... 135
IV.6.1.2 Widmanstätten morphology .................................................................................. 140
IV.6.1.3 Conclusion ............................................................................................................ 143
IV.6.2 Influence of the phase morphology .............................................................. 143
IV.6.3 Conclusions................................................................................................. 145
IV.7 Limits of the technique .......................................................................... 146
IV.7.1 A time consuming technique ....................................................................... 146
IV.7.2 Effect of sliding at the δ/γ boundaries and consequence on the strain
calculation .................................................................................................................. 147
IV.7.3 A 2-dimensional measurement .................................................................... 147
IV.7.4 Limitations due to experimental conditions .................................................. 150
IV.8 Perspective: derivation of per-phase flow properties ......................... 151
IV.8.1 Introduction ................................................................................................. 151
IV.8.2 Microstructure modelling ............................................................................. 151
IV.8.2.1 Image processing of the SEM micrograph ............................................................ 152
IV.8.2.2 Discretization of the microstructure ....................................................................... 153
IV.8.2.3 Optimization of flow properties .............................................................................. 153
IV.9 Conclusions ............................................................................................ 160
Chapter V. Conclusions and perspectives ...................................... 161
V.1 Summary of the chapters III and IV ....................................................... 162
V.1.1 Chapter III ................................................................................................... 162
V.1.2 Chapter IV ................................................................................................... 163
V.2 Recommendations for an optimized microstructure .......................... 164
V.3 Perspectives ........................................................................................... 164
V.3.1 Essential work of fracture concept ............................................................... 164
V.3.2 Modified microgrid technique ....................................................................... 165
Bibliography ...................................................................................... 167