Molecular Dynamics Simulations of the Tensile Mechanical Responses of Selective Laser-Melted Aluminum with Different Crystalline Forms

Abstract

The mechanical deformation of cellular structures in the selective laser melting (SLM) of aluminum was investigated by performing a series of molecular dynamics (MD) simulations of uniaxial tension tests. The effects of crystalline form, temperature, and grain orientation of columnar grains on the mechanical properties of SLM aluminum were examined. The MD results showed that the tensile strength of SLM aluminum with columnar grains at different temperatures was lower than that of single-crystal aluminum, but greater than that of aluminum with equiaxed grains. The tensile strength and Young’s modulus both decreased approximately linearly upon increasing the temperature. The deformation mechanisms of equiaxed and columnar grains included dislocation slip, grain boundary migration, and torsion, while the deformation mechanisms of single crystals included stacking fault formation and amorphization. Finally, the influence of the columnar grain orientation on the mechanical properties was studied, and it was found that the Young’s modulus was almost independent of the grain orientation. The tensile strength was greatly affected by the columnar grain orientation. Reasonable control of the grain orientation can improve the tensile strength of SLM aluminum.

A Molecular Dynamics Simulation to Shed Light on the Mechanical Alloying of an Al-Zr Alloy Induced by Severe Plastic Deformation

“…The stress-strain curves for the samples with GB segregations do not show negative shear stress values because segregations allow a less catastrophic release of the elastic strain energy. Note that negative stress values after critical events associated with sudden structure rearrangement have been observed in many other molecular dynamics simulations [45][46][47].…”

“…The results for pure Al shown in Figure 3 can be compared with the results of previous molecular dynamics studies. Single-crystal Al shows an ultimate strength from 6 to 8 GPa [46][47][48], depending on the loading scheme and simulation conditions, while polycrystalline samples show much lower strength of about 1 GPa [47,49,50]. In our simulations, parallel GBs are considered, and the ultimate shear stress is about 0.2 GPa.…”

“…As a test, the stress-strain curves under uniaxial tensile loading at T = 300 K, with a strain rate of 10 8 s −1 , were calculated and compared with the results presented in [46,47,49]. The ultimate stress between 7.5 and 8 GPa and the critical strain of about 15% were obtained.…”

A Unified Empirical Equation for Determining the Mechanical Properties of Porous NiTi Alloy: From Nanoporosity to Microporosity

“…The resulting porous samples were subjected to uniaxial tensile stress along the OX axis at the constant rate 1.0 × 10 10 s −1 . It is important to note that such ultra-high strain rates are typical for the molecular dynamics simulation method used to study the process of material destruction under high dynamic loading [66,67]. This rate differs from the experimental strain rate, which can lead to overestimation of mechanical properties in the case of molecular dynamics simulation, for example, as shown in Refs.…”

A Review of the Latest Developments in the Field of Additive Manufacturing Techniques for Nuclear Reactors

“…With the development of digital data and machine learning, data-driven modeling has emerged as an effective approach and as a key building block of various AM design and management frameworks, such as design for AM [65], digital twin for AM [66], smart AM [67,68] and cloud AM [69]. Moreover, the molecular dynamic method was used to investigate the effects of crystalline form, temperature, and grain orientation of columnar grains on the mechanical properties of SLM aluminum, which showed that reasonable control of the grain orientation can improve the tensile strength of the AM materials [70]. The Green's function of stresses was used to present the thermal stresses and the Johnson-Cook flow stress model was used to predict the yield surface of the part under repeated heating and cooling [71].…”