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Mg在室温下的强度和塑性较差,其根源之一在于Mg的{10■2}形变孪晶在极低的应力下即可形核和扩展,而且研究表明目前应用于镁合金的时效强化法通常无法显著抑制{10■2}形变孪晶.尽管对Mg及其合金的力学性能至关重要,迄今为止,对{10■2}形变孪晶的形核和扩展的机制仍存在很大争议.本文首先回顾了有关形变孪晶的定义以及{10■2}孪晶机制的研究历史,然后着重介绍了最新的基于原位TEM的研究结果:即Mg的{10■2}形变孪晶迥异于孪晶的经典定义,它事实上是一种新的室温变形机制,即塑性的产生可以通过局部的晶胞重构来完成,而不需要孪晶位错的参与;由晶胞重构机制所产生的界面为{0002}/{10■0}界面(BP界面),而且该界面在三维空间呈现梯田状的不规则形貌.晶胞重构机制迥异于基于位错的孪晶变形机制,因此基于对该机制进行抑制的设计思路可能是开发未来高强韧镁合金的关键.
Mg is poor in strength and ductility at room temperature. One of the reasons for this is that the {10 ■ 2} deformation twin of Mg can nucleate and expand under extremely low stress. Studies have shown that the aging strengthening applied to magnesium alloys Method generally can not significantly inhibit the {10 ■ 2} deformation twins. Although the mechanical properties of Mg and its alloys are of crucial importance, the mechanism of nucleation and propagation of {10 ■ 2} deformation twins has so far been very large This dissertation first reviews the definition of twins and the research history of {10 ■ 2} twins, and then highlights the latest research results based on in-situ TEM: the {10 ■ 2} deformation twin of Mg Different from the classic definition of twins, it is actually a new room-temperature deformation mechanism, that is, the plasticity can be achieved by local unit cell reconstruction without the involvement of twin dislocation; The interface generated by the mechanism is the {0002} / {10 ■ 0} interface (BP interface), and the interface presents a terraced irregular appearance in the three-dimensional space.The mechanism of unit cell reconstruction is very different from that based on dislocation Mechanism, the design idea based on the suppression of this mechanism may be to develop the future high tough The key to magnesium alloy.