双模态纳米孪晶金属材料的力学性能研究

Mechanical properties of nanotwinned metals with bimodal twin spacing distribution

针对双模态孪晶尺寸分布纳米孪晶多晶金属材料,结合双模态微结构尺寸分布的复合结构变形机制和纳米晶/纳米孪晶强化机理,在细观力学框架内考虑变形过程中微裂纹的产生极其对变形行为的影响,建立基于变形机理的塑性力学模型,探究此类纳米结构金属材料的应力-应变关系;分析屈服强度和延展性与相关参数的定量关系。计算结果表明:随着孪晶尺寸的减小,材料的强度和塑性性能均得到提高;同时,材料强度随着增强相的体积分数增大而增强,但塑性有所削弱,因此,可以通过优化不同孪晶尺寸组合以及选取合适体积分数得到强度和塑性良好的金属材料;该工作可为获得高强高韧纳米孪晶复合金属材料的制备提供理论指导。

For nanotwinned polycrystalline metals with a bimodal twin spacing distribution,a mechanism-based micromechanical model was developed through involving the strengthening mechanisms in the bimodal nanostructured metals and nanograined/nanotwinned,and considering the contribution of microcracks generated during deformation and the corresponding influence on the deformation behavior,to investigate the stress-strain response and to analyze the quality relationship between the yield strength,ductility and the related parameters.Numerical results demonstrated that the decrement of twin spacing leads to the improvement of strength and ductility simultaneously.The yield strength was enhanced with increasing volume fraction of strengthening phase,accompanied with a weak drop of ductility.Therefore,high yield strength and high ductility can be obtained through optimizing the twin spacing and the volume fraction of the constituents.The present results could be useful for the preparation of nanotwinned composite metals with super strength and toughness.