Hydrogen embrittlement in a Mg-Al alloy

Characterisation of stress corrosion cracking (SCC) of Mg–Al alloys

“…DHC has been proposed as the mechanism for TGSCC of Mg alloys, although evidence for this is limited [11][12][13][14]. Our numerical model for DHC in Mg predicted crack propagation velocities in the lower range of those reported by previous workers; however, the results were based on speculative values for the H diffusion coefficient and solvus concentration [15].…”

“…The HE models that may be applicable for Mg alloys are: hydrogen enhanced decohesion (HEDE); hydrogen enhanced localised plasticity (HELP); adsorption-induced dislocation emission (AIDE); and delayed hydride cracking (DHC). AIDE [10] and DHC [11][12][13][14][15] have been proposed for TGSCC of Mg alloys; however, the evidence for both mechanisms is limited. HEDE and HELP also remain possible mechanisms.…”

Stress Corrosion Cracking of Magnesium Alloys

“…A DHC model was formulated with the following components: (i) transient H diffusion towards the crack tip driven by stress and H concentration gradients; (ii) hydride precipitation as the H solvus is exceeded; and (iii) crack propagation through the hydride when it reaches a critical size of ~0.8 µm (the distance between crack arrest markings from [42] ). The stress corrosion crack velocity, V c , was calculated from the time, t, for the hydride to reach the critical size as V c = (0.8 µm)/t.…”

Stress Corrosion Cracking Behavior of Fine-Grained AZ61 Magnesium Alloys Processed by Equal-Channel Angular Pressing

“…The fracture surfaces of the as-cast sample that failed in air and in distilled water are shown in Figure 6a,b, respectively. Figure 6a reveals mixed mode with transgranular cleavage and dimpled features, as well as intergranular fracture, mainly initiated by preferential anodic dissolution of the matrix adjacent to β-Mg17Al12 [1], whereas the same sample tested in distilled water showed a predominantly transgranular feature with parallel facets, attributed to hydrogen-assisted embrittlement for the AZ series alloys [5,19,20]. The primary conclusion is that the as-cast AZ61 Mg alloy behaved fairly susceptible to SCC in distilled water.…”