Weak Size-Dependent Strength and Extreme Plastic Deformation of Single Crystal Cu Microparticles

Single crystal Cu microparticles with varied sizes and good crystallinity were batch-fabricated by a flash arc synthesis (FAS) method. The size and extreme plastic deformation-dependent mechanical behaviors of Cu microparticles were investigated through in situ mechanical tests under scanning electron microscopy (SEM). It is noted that the Cu microparticles exhibit near theoretical strength at much larger sizes by comparison with reported values, accompanied by the weak size effect on strength, which we attribute to the high quality of the prepared Cu microparticles. Besides, the hardness of precompressed Cu microparticles increases sharply with the increase of the residual strain, which we attribute to the obstruction of dislocation movement by the drastically increased contact interfaces during extreme plastic deformation and the high hydrostatic pressure induced by friction at the contact interfaces. Then, an extended Taylor hardening model is developed to quantify the residual strain-dependent hardness.