Mechanism of twin-detwinning activity and influence on mechanical properties

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Influence of second phase on activity of twinning in magnesium alloys were investigated by experimental observation and numerical calculations. Experimentally, tension after compression and compression after tension were compared for magnesium alloys with different volume fractions of second phase. Numerically, a crystal plasticity finite element method considering twinning and de-twinning were developed and applied to the two different loading histories to interpret the experimental results. The results showed that stress-strain curves were different depending on tensile or compressive preloading because the activity of twinning was different in tension and compression due to frequency of favorably oriented grains for twinning even in cast alloy with random texture. Furthermore, it was suggested that the difference of stress-strain curves was dependent on frequency of twinning for each material with different volume fraction of secondary phase.