Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
2 Table of contents
II.2.3 Strain partitioning ..............................................................................................33
II.2.4 Influence of the deformation mode ....................................................................35
II.2.5 Influence of the phase morphology ...................................................................36
II.3 Damage during hot working .................................................................... 37
II.3.1 Influence of the chemical composition ...............................................................37
II.3.1.1 Influence of the major elements .............................................................................. 38
II.3.1.2 Influence of the minor elements .............................................................................. 39
II.3.2 As-cast microstructures .....................................................................................40
II.3.3 Influence of temperature and strain rate ............................................................41
II.3.4 Origin of damage...............................................................................................42
II.4 Conclusions .............................................................................................. 43
Chapter III. Hot cracking resistance .................................................. 45
III.1 Literature review about the Essential Work of Fracture concept ......... 45
III.2 Experimental procedure .......................................................................... 49
III.2.1 High temperature testing ...............................................................................49
III.2.2 Dimensions of the DENT specimens .............................................................50
III.2.3 Characterization tools ....................................................................................51
III.2.3.1 Observation of the fracture surfaces ....................................................................... 51
III.2.3.2 Microstructural characterizations ............................................................................ 52
III.2.3.3 Damage characterization ........................................................................................ 52
III.2.3.4 Inclusion content ..................................................................................................... 53
III.2.3.5 Micro-hardness ....................................................................................................... 54
III.3 Comparison between as-cast D1 and D2 ............................................... 54
III.3.1 Results ..........................................................................................................54
III.3.1.1 EWF results ............................................................................................................. 55
III.3.1.2 Fracture observations ............................................................................................. 56
III.3.1.3 Damage ................................................................................................................... 58
III.3.2 Discussion .....................................................................................................60
III.3.2.1 Origin of the differences between D1 and D2 in the as-cast conditions ................. 60
III.3.2.2 Origin of the dispersion of the results ..................................................................... 63
III.3.3 Conclusions...................................................................................................65
III.4 Generation of model microstructures .................................................... 65
III.4.1 Materials and characterizations .....................................................................66
III.4.2 γ-Widmanstätten microstructure ....................................................................66
III.4.2.1 Understanding of the as-cast slab microstructure .................................................. 66
III.4.2.2 Generation of a γ-Widmanstätten microstructure ................................................... 68
III.4.3 γ-Equiaxed microstructure .............................................................................69
III.4.4 Conclusions...................................................................................................71
III.5 Comparison between D1 and D2 γ-Widmanstätten microstructures ... 72
III.5.1 Results ..........................................................................................................72
III.5.1.1 EWF results ............................................................................................................. 72
III.5.1.2 Fracture and damage observations ........................................................................ 74
III.5.2 Discussion .....................................................................................................76