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Examination of mechanical behaviour of aged duplex steel using X-ray and neutron diffraction methods

Baczmański A., Dakhlaoui R., Braham C., Wierzbanowski K.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 1

89-96

EN

The parameters characterizing the elastoplastic mechanical behaviour of each phase in austeno-ferritic duplex stainless steels were determined using X-ray and neutron diffraction during a uniaxial tensile test. The elastoplastic self-consistent model was used to predict the evolution of the lattice elastic strains during loading and to identify the critical resolved shear stresses and work hardening parameters of the material. The effect of ageing treatment on the elastoplastic behaviour of both phases was also studied. It was found that thermal ageing of austeno-ferritic steel caused microstructural transformations and consequently a significant increase of the hardness of ferrite, while the mechanical properties of austenite remained practically unchanged.

PL

Parametry opisujące własności sprężysto-plastyczne każdej z faz w nierdzewnej stali austeno-ferrytycznej zostaly wyznaczone przy użyciu dyfrakcji rentgenowskiej i neutronowej podczas testu rozciągania in situ. Zastosowano sprężysto-plastyczny model samo-uzgodniony do przewidywania sprężystych odkształceń sieci podczas próby rozciągania oraz do wyznaczenia krytycznych naprężeń ścinających na płaszczyznach poślizgu i parametrów umocnienia materiału. Zbadano również efekt wplyw starzenia na własności sprężysto-plastyczne obu faz. Stwierdzono, że proces termicznego starzenia stali austeno-ferrytycznej spowodowal transformacje mikrostrukturalne i w konsekwencji wyrainy wzrost twardoki ferrytu, podczas gdy własności mechaniczne austenitu pozostaly praktycznie niezmienione.

2

Magnetic ordering schemes in R3T4X4 compounds

Wawrzyńska E., Szytuła A.

Materials Science Poland

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2006

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Vol. 24, No. 3

543--549

EN

This work is an attempt of a systematization of the magnetic structures of the R3T4X4 (R - a rare earth atom, T - a transition metal, X - a p-electron element) compounds investigated by means of neutron diffraction in the course of a broader research programme . The experiments were performed for twenty samples containing Pr, Nd, Tb, Dy, Ho and Er. Although the determined structures display a huge variety, some regularities were found for them. The authors try to use different approaches in order to elucidate the observed behaviors and come to some conclusions concerning the factors responsible for the found magnetic ordering schemes.

3

The effect of heat input on residual stress distribution of steel welds measured by neutron diffraction

Paradowska A. M., Price J. W. H., Ibrahim R., Finlayson T. R.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

385--388

EN

Purpose: of this paper is to investigate the effect of increase in the value of heat input due to change in the welding speed and its influence on residual stress distribution in steel weldments. Design/methodology/approach: The use of the neutron diffraction (ND) technique for residual stress measurements is described. Fully restrained, single-bead-on-plate specimens have been examined. Detailed measurements within a small gauge volume were taken 1.5 mm below the surface, across the sample. In addition, studies of macrostructure and hardness were conducted. Findings: Residual stresses in restrained welds and weld repairs are very complex. The heat input affects the value and distribution of residual stress in the specimen. This peak stress in all three samples occurred not at the toe, but in the middle of the weld bead, where the yield stress is higher. The transverse residual stresses of around half the maximum value of longitudinal stress have been observed. Research limitations/implications: Measurements of residual stress can be very expensive and time consuming. The ND technique is capable of non-destructive investigation in a relatively small gauge volume in depth of the material. However, a number of important issues still remain puzzling, including the uncertainties in the measurement, reliability and interpretation of the results, particularly in regards to the sampling volume and generally in the lack of an engineering standard procedure. The results may be used to calibrate finite element modelling of the welding process. Practical implications: The findings have important consequences with respect to design of welding procedures and fitness-for-purpose assessments. Originality/value: The authors have used ND assessment of residual stresses to follow in detail the changes due to heat input in a small gauge volume. This paper could be an interesting source of information for engineers and researchers who work with welded structures

4

Evaluation of residual stresses induced by fatigue cycling in AA359+20% SiCp brake drums using neutron diffraction

Albertini G., Fiori F., Giuliani A., Rustichelli F.

Kompozyty

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2003

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R. 3, nr 7

260-264

EN

Neutron diffraction experiments for the evaluation of residual stresses induced by fatigue cycling in metal-matrix composite (MMC) automotive components are presented. The studied components are three brake drums, manufactured by Teksid a/Centro Ricerche FIAT. One of them was used to study the residual stress state in the as-cast condition. The other two brake drums were submitted to fatigue cycling (,,bench tests"), respectively not-leading and leading to failure. The macro- and micro-stress components are evaluated and compared for the three studied components.

PL

Przedstawiono próby wykorzystania dyfrakcji neutronowej do oszacowania naprężeń wewnętrznych wywołanych cyklicznym obciążeniem zmęczeniowym w elementach dla przemysłu motoryzacyjnego wykonanych z kompozytu o osnowie metalowej (MMC). Badanymi elementami są trzy bębny hamulcowe, wyprodukowane przez Teksid/Centro Ricerche FIAT. Jeden z nich był wykorzystany do zbadania stanu naprężeń wewnętrznych w stanie lanym. Pozostałe dwa bębny hamulcowe zostały poddane laboratoryjnej próbie zmęczeniowej pod cyklicznym obciążeniem, w jednym przypadku prowadzącym, a w drugim nieprowadzącym do zniszczenia. Oszacowano i porównano składowe makro- i mikronapreżeń dla tych trzech badanych elementów.

5

Single-crystal neutron study on cobalt iodate tetrahydrate, a compound with H...|I(V)O3- hydrogen bonds?

Nagel R., Kümmerle E., Lutz H. D.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 1

51-66

EN

The crystal structure of cobalt iodate tetrahydrate Co(IO(3)(2)-4H(2)O (space group P21/c, Z=2, a=836.8(5) pm, b=656.2(3) pm, c=850.2(5) pm, and Beta=100.12°, final Rl = 0.0349 (I>i mniejszości 2 sigma(I) for 1031 unique reflections) was redetermined by single-crystal neutron diffraction studies. The structure is built up by layers parallel (100) connected by interionic O(3)I(-..'OIO(-)(2) bonds. Unequivocal interpretation of the four differently strong OH(...) OIO(-3) hydrogen bonds of the two crystallographic different hydrate H(2)O molecules of the isostructural series M(IO3)(2)-4H(2)O (M = Mg, Co, Ni) on the basis of the observed hydrogen-bond distances and assignment to the uncoupled OD stretching modes of matrix isolated HDO molecules is only possible if weak hydrogen bonds to the iodine lone-pairs of adjacent IO-(3) ions are additionally considered. The potential strength of H(...)I(V)O-(3) hydrogen bonds with respect to H(...) I distances and H(...)IO(-)(3) angles is discussed. A bond-valence concept for estimating the strength of H(...I)I(V)O(-)(3) hydrogen bonds is given.