LAUSR

ABSTRACT A novel one-step approach named large-load and low-speed friction stir processing was developed to produce an ultrafine-grain structure in 70/30 brass. The material so processed was characterised by a mean grain size of 0.5 µm and high angle boundaries of 91%. Abundant twin boundaries and stacking fault were produced in the grains as well. The grain refinement mechanism is attributed to the combination of discontinuous dynamic recrystallisation (DRX), microshear bands assisted DRX and twinning-induced DRX. A good combination of yield strength and uniform strain was achieved. This study provides a simple and effective method to improve the microstructure and mechanical properties in metals and alloys with low stacking fault energy.