A. Ravindra et al., INFLUENCE OF HYDROGEN CHARGING ON MECHANICAL-PROPERTIES OF GAS TUNGSTEN ARC WELDMENTS OF ALUMINUM-LITHIUM ALLOY-8090, Journal of Materials Science, 29(5), 1994, pp. 1203-1212
The effect of hydrogen charging on the mechanical properties of gas tu
ngsten arc welds (GTAW) of aluminium-lithium alloy 8090 (2 mm thick ro
lled sheets) was studied using cathodic hydrogen charging. To stimulat
e an increased amount of hydrogen into welds, the charging current den
sity was increased through a galvanostatic circuit. The deleterious ef
fect of hydrogen on ductility is documented in terms of degradation in
tensile ductility (reduction in area and elongation-to-failure). Micr
oscopic analysis was performed to characterize the microstructure and
grain morphology of the weldments. Hardness measurements revealed an i
ncrease in hardness of the charged welds over the uncharged counterpar
t. Scanning electron microscopy observations of uncharged welds reveal
ed a mixed mode failure with predominantly ductile rupture. Although,
the charged welds exhibited a near similar mode of failure to that of
the uncharged welds, extensive planar slip deformation was observed ne
ar the outer surface of the uncharged welds. The change in fracture mo
de from the outer surface to the central portion of the charged welds
is attributed to intrinsic differences in hydrogen densities. An attem
pt has been made to rationalize the role of hydrogen on tensile proper
ties and quasi-static fracture behaviour of the GTAW welds.