Initiation of Intergranular Fatigue Cracks in Annealed Pure Aluminum

Initiation of fatigue cracks in AZ91 Mg alloy processed by ECAP

Mechanism of fatigue crack initiation was investigated in ultrafine-grained (UFG) magnesium alloy AZ91 processed by equal channel angular pressing (ECAP). Fatigue behaviour of UFG material was compared to the behaviour of material in an initial as-cast state. Focused ion beam technique (FIB) was applied to reveal the surface relief and early fatigue cracks. Two substantially different mechanism...

Initiation of cracks in dental amalgam.

The force required to initiate cracks in dental amalgam beams was measured and related to the microstructure. The force measured was dependent on age and on the distribution of phases on the tension side of the beam. The Ag-Cu phase is most resistant to failure in Dispersalloy and an experimental alloy.

Onset Frequency of Fatigue Effects in Pure Aluminum and 7075 (AlZnMg) and 2024 (AlCuMg) Alloys

The viscoelastic response of pure Al and 7075 (AlZnMg) and 2024 (AlCuMg) alloys, obtained with a dynamic-mechanical analyzer (DMA), is studied. The purpose is to identify relationships between the viscoelasticity and fatigue response of these materials, of great interest for structural applications, in view of their mutual dependence on intrinsic microstructural effects associated with internal...

Reversible twinning in pure aluminum.

Twinning in metals is normally a permanent plastic deformation mechanism. Here we report reversible twinning in high stacking fault energy (SFE) aluminum. Twinning and spontaneous detwinning at the crack tip have been captured in situ during tensile straining under a transmission electron microscope. Both the in situ observation and the molecular dynamics simulations reveal a two-stage detwinni...

Sonic Infrared Imaging of Fatigue Cracks