Microstructure evolution during heat treatment of Mg-Gd-Y-Zn-Zr alloy and its low-cycle fatigue behavior at 573K

In as-cast Mg?2.1Gd?1.1Y?0.82Zn?0.11Zr(mole fraction,%)alloy,lamellar microstructures that extend from grain boundaries to the interior ofα-Mg grains are identified as clusters ofγ′using a scanning transmission electron microscope equipped with a high-angle annular dark-field detector.Under a total strain-controlled low-cyclic loading at573K,the mechanical response and failure mechanism of Mg?2.1Gd?1.1Y?0.82Zn?0.11Zr alloy(T6peak-aging heat treatment)were investigated.Results show that the alloy exhibits cyclic softening response at diverse total strain amplitudes and573K.The experimental observations using scanning electron microscopy show that the micro-cracks initiate preferentially at the interface between long-period stacking order structures andα-Mg matrix and extend along the basal plane ofα-Mg.The massive long-period stacking order structures distributed at grain boundaries impede the transgranular propagation of cracks.

核心素养视域下若干关系的“思”与“辩”

核心素养的培养既需要专家、学者作更为扎实的基础性研究，也需要一线教师有捍卫常识的思考取向和遵循规律、敦行不怠的实践追求，更需要一线教师就培养过程中所遇真实问题的理性思考。基于此，笔者从实践、微观的层面，就核心素养培养过程中的一些“关系”或问题作思辨性的分析，以促进核心素养的落实。