Deformation-Induced Crystal Growth or Redissolution, and Crystal-Induced Strengthening or Ductilization in Metallic Glasses Containing Nanocrystals

It is generally known that the incorporation of crystals in the glass matrix can enhance the ductility of metallic glasses (MGs), at the expense of reduced strength, and that the deformation of MGs, particularly during shear banding, can induce crystal formation/growth. Here, we show that these known trends for the interplay between crystals and deformation of MGs may hold true or become inverted depending on the size of the crystals relative to the shear bands. We performed molecular dynamics simulations of tensile tests on nanocrystal-bearing MGs. When the crystals are relatively small, they bolster the strength rather than the ductility of MGs, and the crystals within a shear band undergo redissolution as the shear band propagates. In contrast, larger crystals tend to enhance ductility at the cost of strength, and the crystal volume fraction increases during deformation. These insights offer a more comprehensive understanding of the intricate relationship between deformation and crystals/crystallization in MGs, useful for fine-tuning the structure and mechanical properties of both MGs and MG-crystal composites.