Simulation of Stresses during Casting of Binary Magnesium-Aluminum Alloys

Abstract

A viscoplastic stress model is used to predict contraction forces measured during casting of two binary Mg-Al alloys. Force measurements from castings that did not hot tear, together with estimates from data found in the literature, are used to obtain the high-temperature mechanical properties needed in the stress model. In the absence of hot tearing, the simulation results show reasonably good agreement with the measurements. It is found that coherency of the semisolid mush starts at a solid fraction of about 0.5 and that the maximum tensile strength for the Mg-1 and 9 wt pct Al alloys at their final solidification temperatures is 1.5 and 4 MPa, respectively. In the presence of hot tearing, the measured stresses are generally overpredicted, which is attributed to the lack of a fracture model for the mush. Based on the comparison of measured and predicted stresses, it is also shown that coupling of the stress model to feeding flow and macrosegregation calculations is needed in order to accurately predict stresses in the presence of hot tearing.

Effect of Start‐Up Levels on the Stress–Strain Field and Cracking Tendency during Direct‐Chill Casting of Magnesium Alloy AZ80

“…Hamdi et al [3] studied the casting process of AA6060 alloy using a finite element model ALSIM, and found the viscoplastic strain rate played an important role for the center cracks. Pokorny et al [4] used a viscoplastic stress model to simulate the stresses during the casting of binary magnesiumaluminum alloys, and the simulation results were reasonably good agreement with the measurements. Hao et al [5] developed a thermomechanical finite element model to simulate the casting of magnesium alloy AZ31, and studied the hot tearing tendency using a pressure-based criterion called Rappaz-Drezet-Gremaud (RDG).…”

“…The values for Q and s 0 are 215.82 kJ mol À1 , [8] 4 MPa, [4] respectively. The strain-rate-sensitivity coefficient m is shown in Figure 2d, drawn from the results of some researches on AZ91 alloy.…”

Effect of Temperature Field and Mechanical Properties of Casting on Prediction of Hot Tearing Tendency Using FEM Thermal Stress Analysis

“…The experimental device developed for this study can obtain the thermal load during solidification under the condition that the contraction was prevented for the two purposes: one is validating the thermal stress analysis through comparison of the analytical value of the load with the experimental one; 1,16,17) the other is determining the crack initiation temperature. 1,1820) For the latter, earlier studies 1820) have revealed that the thermal load increased with the progress in freezing under the condition that the solidification contraction was prevented.…”

Phase-field simulation of dendritic growth under externally applied deformation

“…Moreover, the mechanical response of the solid itself shows strain rate dependency (i.e. [8]). In-situ observations of the deformation behavior of a semi-solid Al-Cu alloy with the X-ray microtomography employed by Terzi et al [9] show that the deformation in the semi-solid is highly inhomogeneous.…”

“…The value is used for simulations in the main chapter. As also mentioned in[58], Poisson's ratio is almost independent of temperature, so a typical value 0.33 is used in this thesis. A static (reference) yield stress ζ 0 varies with temperature.…”