3-D granular modeling and in situ X-ray tomographic imaging: A comparative study of hot tearing formation and semi-solid deformation in Al–Cu alloys

Abstract

The mechanical behavior of partially solidified Al-Cu alloys is investigated to assess the influence of mushy zone deformation on hot tearing. For this purpose, the results of a semi-solid tensile test conducted in situ using X-ray microtomography are compared with the predictions of a coupled hydromechanical granular model in order to both validate the predictions of the model and explain the experimental observations. It is shown that hot tears initiate in the widest liquid channels connected to the free (oxidized) surfaces as long as there is contact between the intergranular liquid and the ambient air. The necking behavior is associated with the deformation-induced liquid pressure drop. Overall, the stresses predicted by the granular model under tensile and shear deformations agree well with the experimental data. Thus, the granular model achieves an important step in predicting hot tearing formation.

Determination of Coherency and Rigidity Temperatures in Al-Cu Alloys Using In Situ Neutron Diffraction During Casting

“…Terzi et al 5 and Sistaninia et al 15 reported that the mechanical instabilities of micropores at the surface of the sample lead to the formation of hot tears. Hot tearing at the hot spot in Sample 1 is explained by a delayed coalescence that starts at a lower coherency temperature and ends with the eutectic formation.…”

Prediction of Hot Tear Formation in Vertical DC Casting of Aluminum Billets Using a Granular Approach

“…During semisolid deformation tests, cracks form on the cast surface because ambient air can fill the growing cavity of the crack. In this situation, the criterion for crack formation is based on the overpressure required to overcome the capillary forces at the liquid-gas interface, 5,6 and thus, a hot tear will form once the liquid pressure in a channel is such that…”

Modeling and characterization of grain structures and defects in solidification

“…The same situation has been simulated with the granular model [68], as shown on the right of Fig. 6.…”

“…The 3D granular simulation result at the same time is shown on the right. The small insert shows the intergranular liquid pressure and the cavitation pressure in the widest liquid channel connected to air, as a function of displacement [67,68]. Fig.…”