Publication
The recent introduction of high entropy alloys presents an exciting opportunity for novel material performance, offering extensive possibilities for tailoring material properties. Dislocation mechanisms in these alloys must be fully understood since they play an important role in defining mechanical properties, such as plasticity and strength. Analytical models based on solute strengthening theory are utilized to investigate dislocation motion in both body-centered (BCC) and face-centered cubic (FCC) high entropy alloys. The analyses reveal that the magnitude and spacing of energy barriers associated with edge dislocations in BCC high entropy alloys are consistent with the models. For FCC metals, a framework is provided for understanding solute strengthening contributions to twinning mechanisms.
Beyond the selection of materials, the choice of fabrication methods also significantly influences the mechanical properties of components. Additive manufacturing of metals stands out as a promising fabrication method, yet several technical challenges persist, including residual stresses, which are particularly problematic as they can potentially lead to critical failures. A considerable number of efforts are underway to develop computational models for the formation of residual stresses, with objectives mostly focused on optimizing parameters to mitigate residual stresses. Most of these models employ various material constitutive laws without assessing the broader impacts of each parameter.
A computational model capturing the thermomechanics of residual stress formation during the additive manufacturing process is developed to run a parametric study. The model calculates and compares the deflection caused by residual stresses in a cantilever beam during the building process. The analysis tests the sensitivity of the parameters of the constitutive law describing the temperature- and strain-rate-dependent mechanical response of high entropy alloys. The study demonstrates the critical influence of the solute strengthening parameter and the rate-dependence of hardening. The sensitivity of the solute strengthening parameter is high at larger values, with up to a 10% change in post-release deflection observed for a 20% increase in this parameter. On the other hand, the rate-dependence of forest hardening exhibits the greatest sensitivity at low values of the solute strengthening parameter, with around a 4% change in deflection observed for a 20% decrease. This assessment will help researchers focus on the critical parameters within their constitutive models and embrace a more comprehensive modeling approach, with results transferable to a broader range of additive manufacturing alloys.