Molecular Dynamics Simulation On Mechanical Behavior Of AlSi10Mg Alloy Prepared By Selective Laser Melting

Aluminum and aluminum alloys have the advantages of low density,good corrosion resistance and easy forming,and have been widely used in the manufacture of complex and special-shaped parts in aerospace,transportation,medical equipment and other industrial fields.Due to the advantages of additive manufacturing technology such as freedom of design and rapid prototyping,the application of selective laser melting(SLM)technology for manufacturing aluminum and aluminum alloy components has been increasingly studied,but the microstructure evolution mechanism of SLMAlSi10 Mg is not yet understood.In this paper,the mechanical properties of SLMAlSi10 Mg are investigated by molecular dynamics(MD).The details of this paper are as follows.(1)The EAM multi body potential is used to simulate the mechanical properties of SLM aluminium.The effects of different crystalline states,temperatures and grain orientation of columnar grains on the mechanical properties of SLM aluminium are mainly investigated.The results show that the tensile strength of SLM aluminium columnar crystals at different temperatures is lower than that of single-crystal aluminium,but greater than that of equiaxed grains aluminium.The tensile strength and Young’s modulus both decrease approximately linearly with increasing temperature.The main deformation mechanisms for single crystals are stacking fault formation and amorphisation,whereas the main deformation mechanisms for equiaxed and columnar grains are dislocation slip,grain boundary migration and torsion.Finally,the effect of grain orientation on the mechanical properties of columnar crystals is investigated,and it is found that Young’s modulus is almost independent of grain orientation.The tensile strength is greatly influenced by the grain orientation of columnar grains.The tensile strength of SLM aluminium can be improved by rational control of grain orientation.(2)The effect of nano-twin and Fe doping on the mechanical properties of SLM aluminium is simulated MD simulations with the EAM multibody potential.The results show that the insertion of nano-twins in different crystalline aluminum can increase the tensile strength of single crystal aluminum,but reduce the tensile strength of equiaxed grains and columnar grains aluminum.Among them,the mechanical properties of columnar grains are the most sensitive to twins,especially the tensile strength.There is a critical value of 2.8 nm for the effect of twin boundary distance λ on the tensile strength of the columnar crystal aluminum.Whenλ is less than this value,the tensile strength of columnar twin aluminum decreases with the increase of λ,while when λ is greater than this value,the tensile strength of columnar grains aluminum gradually increases with the increase of λ,until it is close to that of columnar grains aluminum with twin-free.Compared with the tensile strength of different crystalline twin Al,the tensile strength of different crystalline twin Al doped with 5 at.% Fe is greater,and the strengthening effect of columnar twin Al-5%Fe is the best,indicating that reasonable control of the content of Fe and nanotwinned crystalline,which are expected to improve the mechanical properties of SLM aluminum.(3)The effect of nanocrack on the tensile mechanical properties of single-crystal/columnar grains SLMAlSi10 Mg is investigated using MD simulations with a mixture of EAM potential,ADP potential and LJ potential.The results show that when the crack width is smaller,the strength of the material has little effect compared to the free-crack model.It is also found that the mechanical properties of different nanocrack growth locations are quite different,and the reasonable control of crack growth locations can improve the mechanical properties of the material.At the same time,the effect of temperature on the mechanical properties of single crystal/columnar crystal of prefabricated nanocrack is also investigated.It is also found that as the temperature increased,the decreasing rate of tensile strength and Young’s modulus increase gradually,and the decrease of tensile strength is the largest.