杂质对铜晶界结合力的影响
Impurity effects on the grain boundary cohesion in copper
摘要：
晶界偏聚的杂质能显著改变金属的力学行为，但其机制在某些情况下仍不清楚。在这里，我们提出了一个统一的方法来调查偏析及其对多晶合金的机械性能的影响，使用的例子3 $sp$杂质（镁，铝，硅，磷，或S）在一个特殊类型的$Σ5(310)[001]$倾斜晶界铜。我们发现，对于这些杂质偏析到晶界的应变贡献的晶界脱粘的工作是小的，化学贡献与铜和杂质之间的电负性差异。应变对位错发射功的贡献为负值，而化学贡献为正值。从Mg到S，随着电负性的增加，应变和化学对位错发射功的贡献一般都变小。通过将这些贡献结合在一起，我们发现，与实验观察一致，S的强偏析可以减少晶界分离的工作低于位错发射的工作，从而脆化Cu，而这种脆化不能由P偏析产生，因为它降低了位错发射的能垒相对大于工作分离。
英文摘要：
Segregated impurities at grain boundaries can dramatically change the mechanical behavior of metals, while the mechanism is still obscure in some cases. Here, we suggest an unified approach to investigate segregation and its effects on the mechanical properties of polycrystalline alloys using the example of 3$sp$ impurities (Mg, Al, Si, P, or S) at a special type $Σ5(310)[001]$ tilt grain boundary in Cu. We show that for these impurities segregating to the grain boundary the strain contribution to the work of grain boundary decohesion is small and that the chemical contribution correlates with the electronegativity difference between Cu and the impurity. The strain contribution to the work of dislocation emission is calculated to be negative, while the chemical contribution to be always positive. Both the strain and chemical contributions to the work of dislocation emission generally become weaker with the increasing electronegativity from Mg to S. By combining these contributions together we find, in agreement with experimental observations, that a strong segregation of S can reduce the work of grain boundary separation below the work of dislocation emission, thus embrittling Cu, while such an embrittlement cannot be produced by a P segregation because it lowers the energy barrier for dislocation emission relatively more than for work separation.
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