Extension twinning is not only a key plastic deformation mode of Mg and its alloys at room temperature (RT), but also introduces high density of dislocations and changes crystal orientation (texture) which exert considerable influence on precipitation strengthening and mechanical properties. Using tensile test, quasi-in-situ hardness test, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), the effects of extension twinning on age-hardening, precipitation behavior and mechanical properties of an extruded AZ80 bar were investigated. Extension twins were introduced into the bar by cold compressed (H1) along extrusion direction (ED), and two kinds of aging treatments, i.e. ‘on-line quenching + aging’ (T5) and ‘on-line quenching + H1 + aging’ (T10), were conducted at 150 °C. We clarified that extension twinning can significantly accelerate precipitation kinetics. For T5 aging, there is an incubation stage in the first 15 h, and then the hardness increases continually and slowly in the following 35 h. By contrast, for T10 aging, softening is caused in the first 2.5 h, and then the hardness increases linearly until 20 h and remains stable in the next 30 h. Discontinuous precipitation is predominant in T5 aging; however, discontinuous precipitation is mostly inhibited in T10 aging and at the same time nano-sized continuous precipitates with high number density are formed in both extension twins and matrixes. Extension twins contains higher dislocation density and thus denser continuous precipitates than matrixes. Both <a> and <a+c> dislocations can be seen in extension twins and matrixes. Mechanical properties have been largely improved by extension twins. Particularly, after T10 the ED tensile yield strength (R_p0.2) remarkably increases from 144 MPa (H1) to 206 MPa, indicating that dense nano-sized continuous precipitates can effectively hinder twin-boundary migration during the detwinning. Moreover, T10 can obviously diminish the machinal property anisotropy as compared with T5.

延伸孪晶不仅是Mg及其合金在室温（RT）下的关键塑性变形模式，而且还引入了高位错密度并改变了晶体取向（质地），这对析出强化和机械性能产生了重大影响。使用拉伸试验，准原位硬度试验，光学显微镜（OM），扫描电子显微镜（SEM）和透射电子显微镜（TEM），延伸孪晶对挤压件的时效，析出行为和力学性能的影响对AZ80棒进行了调查。通过沿挤压方向（ED）的冷压缩（H1）将拉伸孪晶引入钢筋，并进行两种时效处理，即“在线淬火+时效”（T5）和“在线淬火+ H1 +时效” （T10）在150℃下进行。我们阐明了延伸孪生可以显着加速沉淀动力学。对于T5老化，在开始的15小时内有一个孵化阶段，然后在接下来的35小时内硬度持续缓慢地增加。相反，对于T10时效，在最初的2.5小时内引起软化，然后硬度线性增加直至20小时，并在接下来的30小时内保持稳定。T5老化主要是不连续的降水。然而，不连续的沉淀在T10时效中被大部分抑制，同时在延伸孪晶和基体中都形成了具有高数密度的纳米级连续沉淀。延伸孪晶具有更高的位错密度，因此比基质具有更高的连续析出物密度。<a>和<a + c>位错都可以在延伸孪晶和矩阵中看到。延伸双胞胎大大改善了机械性能。特别是在T10之后，ED拉伸屈服强度（R_p0.2）从144 MPa（H1）显着增加到206 MPa，表明致密的纳米级连续沉淀物可以有效地阻止脱孪过程中的双边界迁移。此外，与T5相比，T10可以明显减小其机械特性各向异性。