Microstructural Effect on Cold Strengthening Mechanism of MP159 Alloys

Previous investigations on MP159 alloys have largely reported the striking reinforcement performance after cold deformation, which the deformation mechanism was attributed to HCP phases and deformed twins and so on. To data, the microstructural effect on cold strengthening mechanism of MP159 alloy was still controversial. In this work, the processes of microstructural evolution were elaborated through multi-scale structural characterizations. In the initial MP159, the recrystallized grains and Σ3 twins (<111> 60°) play a dominant role in the microstructures. After cold drawing, the microcosmic dislocations were significantly increased in the deformed grains. The mesoscopic Σ3 twins were seriously deformed to become the deformed twins, inducing that the grains were refined. Meanwhile, the grain boundaries were broken and the HAGBs were subsequently transformed to the LAGBs. The microstructural transition of dislocations → LAGBs ← HAGBs was confirmed. The high stacking fault energy in the deformed twins promoted a high strain energy stored in the MP159, forming the macroscopical <111> //RD texture. The series of microstructural changes induced the significant enhancement of the strength and hardness. The microstructural effect on cold strengthening mechanism of MP159 alloys was clarified, which would be a great significance to strengthening metallic materials in the current investigations. Graphical Abstract