Effect of Periods on Plastic Deformation of Al/Ti Self-propagation Welds by Molecular Dynamics Study

A molecular dynamics approach was used to simulate the self-propagation exothermic reaction of Al/Ti nano-multilayers to achieve Al/Ti dissimilar metal connection, and the tensile properties of Al-Ti post-weld components were investigated at different periods, tensile temperatures and strain rates. The results show that the yield strength of the post-welded components decreases from 6.23 GPa to 4.07 GPa with the increase of the periods from 3 to 7, and the Young's modulus also show decreasing trend. In uniaxial tensile loading deformation, Shockley imperfect dislocations dominate the system. When the period is 3, the high dislocation line density is favorable to obtain the best mechanical properties of the post-weld components, and the Young's modulus of the Al/Ti post-weld components is 27.3% higher than that of single-crystal aluminum of the same size. With the increase of tensile temperature, the yield strength of the post-welded components decreases from 6.23 GPa to 2.25 GPa and Young's modulus decreases from 87.41 GPa to 53.98 GPa, both of which show a decreasing linear trend. When the tensile temperature is 100 K, a large number of dislocation entanglements act as a barrier to dislocation slip in the system, effectively improving the mechanical properties of the material. With the decrease of strain rate, the yield strength of welded members decreases from 7.84 GPa to 3.87 GPa, and the mechanisms of endowment layer dislocations, external layer dislocations, and twin crystal formation are found and revealed in plastic deformation. The sensitivity of the yield strength to the internal dislocation response of the post-welded component is high at high strain rates, and the yield strength of the material reaches a maximum value of 7.84 GPa, where the slip and deformation of dislocations are the main deformation mechanisms.