Grisignano di Zocco, Italy
Grisignano di Zocco, Italy

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Santuliana E.,University of Trento | Cristofolini I.,University of Trento | Molinari A.,University of Trento | Libardi S.,TFM Group | Marconi P.,2Effe Engineering
Advances in Powder Metallurgy and Particulate Materials - 2010, Proceedings of the 2010 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2010 | Year: 2010

The effect of shot peening on the plane bending fatigue of a 7.2 g/cm 3 0.5%C Cr-Mo sintered steel was investigated. Shot peening experiments were first carried out with different parameters (shot diameter and hardness, coverage) and surface densification, work hardening and residual stresses were monitored. The dimensional and geometrical characteristics of the shot peened specimens were measured, as well. The improvement in the fatigue resistance is noticeable, up to 30% with respect to the as sintered material. © 2010 Metal Powder Industries Federation.


Molinari A.,University of Trento | Santuliana E.,University of Trento | Cristofolini I.,University of Trento | Rao A.,University of Trento | And 2 more authors.
Materials Science and Engineering A | Year: 2011

The effect of shot peening on the plane bending fatigue strength of a 7.1g/cm3 sintered Cr-Mo steel was investigated. Shot peening provides surface densification, strain hardening, compressive residual stresses up to -700MPa, without impairing the dimensional and geometrical precision of specimens. Plane bending fatigue strength increases of 30%, irrespective to the different residual stress profiles obtained by changing the shot peening parameters. The improvement is mainly due to the surface densification and strain hardening. © 2010 Elsevier B.V.


Cristofolini I.,University of Trento | Pilla M.,University of Trento | Rao A.,R and D Key RK S.r.l. | Libardi S.,TFM Group | Molinari A.,University of Trento
International Journal of Precision Engineering and Manufacturing | Year: 2013

The effect of the sintering and sinter-hardening temperature on the dimensional and geometrical precision of ring-shaped parts was investigated. The parts were produced with a 3%Cr-0.5%Mo-0.5%C steel, compacted to 6.8 g/cm3 and sinter/sinter-hardened at 1250°C, 1300°C and 1350°C. The increase in the sintering temperature enhances the fraction of load bearing section and leads to an expected significant improvement of mechanical properties. Dimensional shrinkage increases with the sintering temperature, however, the dimensional and geometrical precision obtained in all the cases is very good even at very high sintering temperature. Dimensional variations are anisotropic, and the effect of anisotropy was estimated by evaluating the lack of precision attained when green parts are designed assuming an isotropic behavior. © 2013 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.


Cristofolini I.,University of Trento | Cristofolini I.,TFM Group | Pilla M.,University of Trento | Pilla M.,TFM Group | And 6 more authors.
Advances in Powder Metallurgy and Particulate Materials - 2010, Proceedings of the 2010 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2010 | Year: 2010

The effect of the sintering temperature on the dimensional and geometrical precision of a 3%Cr-0.5%Mo- 0.5%C ring-shaped part produced in an industrial plant was studied. The part was compacted to 6.8 g/cm3 green density and sinter-hardened at 1120°C, 1250°C, 1300°C and 1350°C. Despite the large shrinkages (up to 1.24% at the highest temperature), dimensional and geometrical characteristics do not worsen noticeably on sintering, except for the dimensional tolerances on the diameter, which anyway keep a good precision level, from IT3 to IT4-IT5 (internal diameter) and from IT5 to IT6-IT7 (external diameter). According to the results, sintering at high temperature up to 1350°C does not seem to impair the most important characteristic of sintered parts, i.e. the precision. © 2010 Metal Powder Industries Federation.


Edgcombe C.J.,TFM Group | Ionescu A.,TFM Group | Loudon J.C.,Electronic Microscopy Group | Blackburn A.M.,Hitachi Cambridge Laboratory | And 2 more authors.
Ultramicroscopy | Year: 2012

Holographic measurements on magnetised thin-film cobalt rings have demonstrated both onion and vortex states of magnetisation. For a ring in the vortex state, the difference between phases of electron paths that pass through the ring and those that travel outside it was found to agree very well with Aharonov-Bohm theory within measurement error. Thus the magnetic flux in thin-film rings of ferromagnetic material can provide the phase shift required for phase plates in transmission electron microscopy. When a ring of this type is used as a phase plate, scattered electrons will be intercepted over a radial range similar to the ring width. A cobalt ring of thickness 20. nm can produce a phase difference of π/2 from a width of just under 30. nm, suggesting that the range of radial interception for this type of phase plate can be correspondingly small. © 2012 Elsevier B.V.


Edgcombe C.J.,TFM Group
Journal of Physics: Conference Series | Year: 2010

The Aharonov-Bohm effect provides a way to change the phase difference between scattered and direct electron waves in the transmission electron microscope by 90 degrees, and so to convert phase variation into amplitude information. In a thin ring of magnetic material a continuous loop of azimuthal flux provides the state of lowest magnetic energy (the vortex state). Permanently-magnetized rings can maintain this flux pattern in the presence of a strong axial field such as that of a microscope objective lens. The radial width required for such a ring is of the order of 50 nm and so the radial fraction of the scattered electrons that is intercepted can be very small. © 2010 IOP Publishing Ltd.

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