As the lightest structural metal, magnesium (Mg) has broad application prospects in 3C electronics, transportation, aerospace and other fields. However, traditional magnesium alloys have problems of low absolute strength and poor room - temperature formability, which limit their wider application. An important reason is that during the deformation process of magnesium alloys, basal <a> dislocations are extremely easy to slide, while the supply of movable <c + a> dislocations is insufficient. As the key carrier for coordinating the plastic deformation of magnesium alloys along the <c> axis, the critical resolved shear stress (CRSS) of <c + a> dislocations is very high, and it is difficult to be activated in large quantities during the deformation process.
Traditional solutions have drawbacks. For example, although alloying with rare - earth elements can promote the activation of <c + a> dislocations, it is costly; severe plastic deformation (SPD) can introduce high - density dislocations, but often seriously damages plasticity due to too many defects.
In this context, the Light Alloy Center team at Shanghai Jiao Tong University proposed an alloy design strategy based on dislocation engineering regulation. Through the combined process of rotary swaging (RS) and flash annealing (FA), this team has successfully improved the strength and ductility of rare - earth - free Mg - Al - Ca alloys. During the rotary swaging process, the alloy undergoes severe plastic deformation. The second - phase and solute in the alloy inhibit twinning during the high - frequency short - range deformation of rotary swaging, so that the deformation is mainly dominated by a large number of <a> and <c + a> dislocations. Since the climb energy barrier of <c + a> dislocations is higher than that of <a> dislocations, in the subsequent flash annealing process, most of the <a> dislocations are annihilated, while a large number of <c + a> dislocations are retained. These retained <c + a> dislocations can continue to slide to coordinate plastic deformation during the subsequent tensile deformation process, thereby improving the ductility of the alloy. At the same time, a large number of crystal defects introduced into the alloy structure by rotary swaging make nano - scale Al - Ca precipitates and atomic clusters extremely easy to form during the flash annealing process.
The formation of these precipitates and atomic clusters further improves the strength of the alloy. Through this "rotary swaging + induction annealing" process, the synergistic improvement of the strength and ductility of Mg - Al - Ca alloys has been achieved, providing new ideas for the microstructure regulation and performance optimization of magnesium alloys. The relevant research results were published in the internationally renowned journal Communications Materials under the title "High strength and ductility in a rare - earth free magnesium alloy processed by rotary swaging and flash annealing". Doctoral student Fan Yunhao is the first author of the paper, Professor Liu Boyu from Xi'an Jiaotong University, Researcher Wang Hao from the Institute of Metal Research, Chinese Academy of Sciences, and Researcher Wang Leyun from Shanghai Jiao Tong University are the co - corresponding authors of the paper, and Shanghai Jiao Tong University is the first unit. The collaborating units also include the Helmholtz - Zentrum Hereon Institute in Germany, Jiangxi University of Science and Technology, Liaoning Materials Laboratory, and Baomake (Hefei) Technology Co., Ltd.
With the continuous improvement of the performance requirements for magnesium alloys, the "rotary swaging + induction annealing" process will be continuously optimized and improved, providing a more solid foundation for the application expansion of magnesium alloys, and allowing magnesium alloys to show their unique advantages and values in more fields.