周期层数对Al/Ti自蔓延焊接构件拉伸性能影响的分子动力学模拟研究

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

    • 摘要: 采用分子动力学方法对通过Al/Ti纳米多层膜自蔓延放热反应实现铝钛异种金属的连接进行模拟,研究了不同周期层数、拉伸温度以及应变速率下铝钛焊后构件的拉伸性能。结果表明,随着周期层数从3增加至7,焊后构件的屈服强度从6.23 GPa降低到4.07 GPa,杨氏模量呈下降趋势。在单轴拉伸加载变形中,Shockley不全位错在体系中占主导地位。当周期层数为3时,较高的位错线密度有利于焊后构件获得最佳力学性能,且焊后构件杨氏模量比相同尺寸单晶铝高27.3%。随着拉伸温度的升高,焊后构件的屈服强度从6.23 GPa下降到2.25 GPa,杨氏模量从87.41 GPa下降至53.98 GPa,均呈线性下降趋势。当拉伸温度为100 K时,体系中大量的位错缠结起到了位错滑移的屏障作用,有效地提高了材料的力学性能。随着应变速率的降低,焊后构件的屈服强度从7.84 GPa下降到3.87 GPa,在塑性变形中发现并揭示了内禀层错、外禀层错以及孪晶的形成机制。在高应变速率下,屈服强度对焊后构件内部位错响应的灵敏度高,材料的屈服强度达到最大值7.84 GPa,位错的滑移和变形是主要的变形机制。

       

      Abstract: 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.

       

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