Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Advances in Materials Science

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Intergranular stress corrosion cracking of friction stir welded nugget on a 2050-T8 aluminum alloy

Dhondt M., Aubert I., Saintier N., Olive J.

Advances in Materials Science

2011

Vol. 11, nr 3(29)

43-50

Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum alloy 2050-T8. The weld nugget consists of fine equiaxed grains having average sizes from 4 to 20 ěm, the grain size increases with decreasing of the distance from the weld surface. The weld nugget contains a particular microstructure called “onion rings” due to crystallographic orientations. The effect of the “onion rings” on stress corrosion cracks initiation is studied for stress corrosion cracking tests at a strain rate of 2.10-6 s-1. EBSD cartographies allow showing that the initiation site of the biggest cracks is located at boundaries between the texture bands. Corrosion and stress corrosion tests in 1.0 M NaCl are performed in order to show stress effect on intergranular corrosion. Pitting corrosion is observed during corrosion tests, whereas intergranular cracks appear during stress corrosion tests. The medium crack length is 20 ěm and 168 cracks per mm2 can be located. In these severe laboratory conditions, the order of magnitude of long crack growth rate is 5.10-8 m.s-1.

Modification of plastic strain localization induced by hydrogen absorption

Aubert I., Plessier F., Saintier N., Olive J.-M.

Advances in Materials Science

2008

Vol. 8, nr 1(15)

5-13

In order to highlight hydrogen effects on the plasticity, the slip morphology after straining (under tension up to 4% of plastic strain in ambient air) of hydrogenated (at 135 wt.ppm) and non-hydrogenated 3161 stainless steel polycrystals was compared. A statistical analysis of both slip band spacings (SBS) and slip band heights (SBH) was performed using atomic force microscopy. Tensile tests were performed at low strain rate, specimens being previously charged at controlled hydrogen concentration. The plastic strain field heterogeneity in polycrystals was taken into account thanks to numerical simulation of crystalline plasticity. On each grain, the calculated plastic shear was correlated with the distribution of SBS and the average number of emerging dislocations per slip band. In comparison with uncharged specimen and for an equivalent cumulated plastic strain, the hydrogenated specimen shows an increase of the slip band spacing (SBS) and of emerging dislocations. This result confirms a plastic localization induced by absorbed hydrogen.