论文部分内容阅读
为了揭示14H相的形成机理,制备并研究了18R LPSO单相Mg-Y-Zn(简称S18)合金经773 K退火100 h的显微组织演变。结果表明:铸态S18合金主要由18R相组成(其体积分数高于93%),并含有少量的W相和α-Mg相。退火时,S18合金中的18R相保持稳定,未转变成14H LPSO结构。然而,在α-Mg相内部形成了14H层片相,其尺寸和体积分数随着退火时间的延长不断增大。TEM分析表明,14H相在α-Mg内基面堆垛层错区域独立形核。14H层片的增厚生长是界面控制过程,与基面台阶的形成密切联系。而14H层片的伸长生长属于扩散控制,与溶质元素的扩散有关。该18R单相合金中14H相的形成机理可通过反应式α-Mg’→α-Mg+14H表示。
In order to reveal the formation mechanism of 14H phase, the microstructure evolution of 18R LPSO single phase Mg-Y-Zn alloy (S18) annealed at 773 K for 100 h was prepared and studied. The results show that as-cast S18 alloy mainly consists of 18R phase (volume fraction higher than 93%), and contains a small amount of W phase and α-Mg phase. During annealing, the 18R phase in the S18 alloy remained stable and did not change to the 14H LPSO structure. However, the 14H lamellar phase was formed inside the α-Mg phase, and its size and volume fraction increased with annealing time. TEM analysis shows that phase 14H nucleates independently in the stacking region of α-Mg inner basal planes. The thickened growth of 14H plies is the process of interface control, which is closely related to the formation of basement steps. However, the elongation growth of 14H sheet belongs to diffusion control, which is related to the diffusion of solute elements. The formation mechanism of the 14H phase in the 18R single phase alloy can be represented by the reaction formula α-Mg ’→ α-Mg + 14H.