Wyniki wyszukiwania - BazTech

1

Optymalizacja charakterystyk wytrzymałościowych żeliwa sferoidalnego ADI na podstawie analizy numerycznej

Dzioba I., Lipiec S.

Autobusy : technika, eksploatacja, systemy transportowe

|

2016

|

R. 17, nr 4

58--63

PL

W artykule przedstawiono wyniki badań numerycznych, przeprowadzonych celem optymalizacji wytrzymałości żeliwa sferoidalnego ADI. Badano wpływ rozmiarów i udziału względnego cząstek grafitu na wytrzymałość osnowy żeliwa. Obliczenia numeryczne przeprowadzono w programie ABAQUS dla płaskiego stanu naprężeń. Na podstawie analizy numerycznej ustalono, że względny udział cząstek ρ = 8% oraz rozmiar średnicy cząstki 8 µm można przyjąć za optymalne.

EN

The paper presents the results of numerical investigation carried out to optimize the strength of austoferritic ductile iron ADI. The influence of size and density of the graphite particles on ductile iron strength were tested. Numerical calculation was performed using program ABAQUS for plain stress state. On the numerical analysis basis it was determined that relative share of particles ρ = 8% and particle diameter equal 8% µm are as optimal.

2

Decarburisation Of Ferrite Laths During Bainite Reaction In Adi

Ławrynowicz Z., Dymski S.

Journal of Polish CIMAC

|

2009

|

Vol. 4, no 3

65-72

EN

The paper presents an investigation of the time required for the diffusion of carbon out of supersaturated laths of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to a larger extent and that the resulting microstructure is not an ausferrite, but is a mixture of bainitic ferrite, retained austenite and carbides. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

3

Carbon diffusion during bainite reaction in austempered ductile iron

Ławrynowicz Z., Dymski S.

Advances in Materials Science

|

2008

|

Vol. 8, nr 1(15)

75-87

EN

The paper presents an investigation of the carbon concentration in the residual austenite and the time required for the diffusion of carbon out of supersaturated subunits of ferrite into the retained austenite. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransforrned austenite indicate that there is a necessity of carbides precipitation from austenite. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austenite and a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison of experimental data with the T0, T0' and Ae3' phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

4

Analysis of carbon diffusion during bainite transformation in ADI

Ławrynowicz Z., Dymski S.

Archives of Foundry Engineering

|

2007

|

Vol. 7, iss. 3

87-92

EN

The paper presents an investigation of the time required for the diffusion of carbon out of supersaturated sub-units of ferrite into the retained austenite. The analytical model estimates the decarburisation time of the sub-units of supersaturated bainitic ferrite. The purpose of the present paper is to demonstrate how a thermodynamic method can be used for solving a problem of the decarburisation of bainite subunits and carbon diffusion distances in the matrix of ADI. This should in principle enable to examine the partitioning of carbon from supersaturated ferrite plates into adjacent austenite and the carbon content in retained austenite using analytical method. The diffusion coefficient of carbon in austenite is very sensitive to the carbon concentration and this has to be taken into account in treating the large concentration gradients that develop in the austenite. The results are discussed in the context of displacive mechanism of bainite transformation. Experimental measurements of volume fraction of bainitic ferrite and volume of the untransformed austenite indicate that there is a necessity of carbides precipitation from austenite. The necessary carbon diffusion distance in austenite also illustrates that the estimated time is not capable of decarburising the ferrite subunits during the period of austempering. A consequence of the precipitation of cementite from austenite during austempering is that the growth of bainitic ferrite can continue to larger extent and that the resulting microstructure is not an ausferrite but is a mixture of bainitic ferrite, retained austenite and carbides.