| Magnesium is considered potential "green materials" in the 21st century forexcellent properties and facility in recycling. The poor plasticity at room temperature anddifficuilty for cold working restrain the development and application of magnesium. ThePresent studies on the mechanism of twinning are macroscopical and qualitative, andstudies on the microcosmic nature of twinning are much less. The main goal for thispaper is to investigate the effects of twinning on the deformation in a microcosmic andquantitative way.In order to obtain textured samples with various grain sizes, magnesium alloy barsare extruded in different extruded ratio. To further investigate the relationship betweengrain size and twinning, the samples are annealled at 420℃for different time. Tensileand compression tests are carried out to reveal the mechanical properties of differentsamples. Optical microscopy (OM) is used for the observation and calculation oftwinning in a quantitative way, the style of twinning is detected by transmission electronmicroscopy (TEM), X-ray diffraction(XRD) is used for exactly measurement of texture.The results show that twinning could make great contribution to the deformation atroom temperature. Mechanical twinning is strongly grain size and texture dependance.Twinning ratio and twinning area fraction is increasing with the growing grain size. Inbasal fiber texture condition, compression along the extruding direction is easier for theactivation of twinning than tensile. The contribution of twinning to strain has reached to50％when the grain size reaches to about 18μm. Twinning makes more contributions tocompression deformation than tensile deformation.
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