| 1. |
- Molnar, David, et al.
(författare)
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Deformation properties of austenitic stainless steels with different stacking fault energies
- 2018
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Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. ; 941, s. 190-197, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- In FCC metals a single parameter – stacking fault energy (SFE) – can help to predict the expectable way of deformation such as martensitic deformation, deformation twinning or pure dislocation glide. At low SFE one can expect the perfect dislocations to dissociate into partial dislocations, but at high SFE this separation is more restricted. The role of the magnitude of the stacking fault energy on the deformation microstructures and tensile behaviour of different austenitic steels have been investigated using uniaxial tensile testing and electron backscatter diffraction (EBSD). The SFE was determined by using quantum mechanical first-principles approach. By using plasticity models we make an attempt to explain and interpret the different strain hardening behaviour of stainless steels with different stacking fault energies.
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| 2. |
- Hansson, Per, et al.
(författare)
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Possibilities with use of electron beam welding of very high strength steel
- 2018
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Ingår i: Mater. Sci. Forum. - : Trans Tech Publications Ltd. - 9783035712087 ; , s. 443-452
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Konferensbidrag (refereegranskat)abstract
- Welding of very high strength steels quenched and tempered steel, Rp0.2 > 700 MPa, put high demands on choice of weld process, consumables and also the heat input used. Such steels commonly have a quite narrow tolerance box for a suitable weld heat input to control the cooling time t 8/5 pertaining to minimize risk for generating weld defects such as undercut, too soft weld heat affected zone, delayed crack risk etc. When welding very high strength steel the cold cracking risk of the weld metal not is negligible due to the high alloy content of such filler wires. Filler metal of equal strength of the parent plate hard to find and under-matching filler wires are commonly used. The interest was directed towards electron beam (EB) welding because of the many new developments in the process recent years. The focus on laser welding technology has in a way moved the research work from (EB) welding. The need of vacuum chambers and restrictions in the manipulation of the EB gun is also factors which give problems in the industrialization of the process. Recent developments in manipulation of EB gun and workpiece generate new possibilities. The Electron Beam Weld process (EBW) has been used to study its possibilities when welding very high strength steel with respect to the cold crack risk of such weldments. The results demonstrate possibilities to achieve strength properties of the weldments of equal properties as has the parent plate, which makes further development/fine-tuning of the EBW-process necessary.
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| 3. |
- Nordstrom, Joakim, et al.
(författare)
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Deformation Twinning Behavior in High Ni-Austenitic Materials
- 2018
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Ingår i: THERMEC 2018: 10TH INTERNATIONAL CONFERENCE ON PROCESSING AND MANUFACTURING OF ADVANCED MATERIALS. - : TRANS TECH PUBLICATIONS LTD. - 9783035712087 ; , s. 1591-1596
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Konferensbidrag (refereegranskat)abstract
- Deformation twinning behaviors have been studied in high Ni alloys, Alloy 28 or Sanicro 28 and Alloy 625 at RT and at cryogenic temperature. The microstructures were evaluated using SEM-EBSD. Some constitutive approach has also been used in the discussion on the deformation twinning in high Ni-alloys. The results show that deformation twinning can occur in high Ni alloys depending on the chemical composition, strain range and stress conditions. TWIP can occur in the Ni based superalloy Alloy 625 at cryogenic temperature, which increases both strength and ductility. This is the first report of this phenomena for this alloy. Deformation twinning in high Ni alloys occurs heterogeneously in the material, depending on crystallographic parameters such as grain orientation and Schmid factor. Formation of deformation twins can lead to high texture in the material, which will contribute to the increase of strength. The mechanisms for the formation of deformation twins in high Ni alloys have been discussed.
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| 4. |
- Saketi, Sara, et al.
(författare)
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Wear behaviour of two different cemented carbide grades in turning 316 L stainless steel
- 2018
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Ingår i: Materials Science Forum. - : TRANS TECH PUBLICATIONS LTD. - 0255-5476 .- 1662-9752. ; 941, s. 2367-2372, s. 2367-2372
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Tidskriftsartikel (refereegranskat)abstract
- Cemented carbides are the most common cutting tools for machining various grades of steels. In this study, wear behavior of two different cemented carbide grades with roughly the same fraction of binder phase and carbide phase but different grain size, in turning austenitic stainless steel is investigated. Wear tests were carried out against 316L stainless steel at 180 and 250 m/mincutting speeds. The worn surface of cutting tool is characterized using high resolution scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES) and 3D optical profiler.The wear of cemented carbide in turning stainless steel is controlled by both chemical and mechanical wear. Plastic deformation, grain fracture and chemical wear is observed on flank and rake face of the cutting insert. In the case of fine-grained, the WC grains has higher surface contact with the adhered material which promotes higher chemical reaction and degradation of WC grains, so chemical wear resistance of the composites is larger when WC grains are larger. The hardness of cemented carbide increase linearly by decreasing grain size, therefore mechanical wear resistance of the composites is larger when WC grains are smaller.
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