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研究了铸态和挤压态Mg_(97)Y_2Zn_1合金中长周期堆垛有序结构在高温退火时的组织演化.结果表明,铸态合金由网状的18R-LPSO相、堆垛层错、α-Mg和少量的Mg_(24)Y_5颗粒组成.经过挤压后,第二相沿挤压方向呈带状分布,同时在基体内析出大量尺寸细小的14H层片.铸态合金退火初期,14H结构在18R周围的层错区内大量形核,随后18R沿着层错向14H层片转变,14H层片不断增厚和增长,并在退火30 h时体积达到最大.此后继续退火时,18R向14H的转变和14H的溶解同时进行,在退火200 h的样品基体内部几乎不存在14H层片,只在18R相周围有少量残余14H结构.对于挤压态合金,由于挤压时大量形核位置的引入,14H晶核在合金中已大量存在.退火时,18R结构不断溶解于基体中直至全部消失,14H层片则随退火时间的延长连续增长和增厚.当14H层片覆盖基体后,继续延长退火时间,14H层片的增长受到α-Mg晶界阻碍,只发生粗化以及溶解过程.在退火200 h的挤压态样品中,只剩下粗化的14H结构.
The microstructure evolution of long-period stacking ordered structures in as-cast and extruded Mg_ (97) Y_2Zn_1 alloys at high temperature annealing was investigated. The results show that the as-cast alloys consist of 18R-LPSO reticulate, stacking faults, α-Mg and a small amount of Mg_ (24) Y_5 particles.After extrusion, the second phase along the extrusion direction of the belt-like distribution, while a large number of small-size precipitation in the matrix 14H layer cast alloy early annealing, 14H The structure was largely nucleated in the fault zone around 18R, and then the 18R transitioned along the fault to the 14H lamellae. The 14H lamellae continuously thickened and grew, reaching the maximum at 30 h after annealing, and 18R The transition to 14H and the simultaneous dissolution of 14H showed that there was almost no 14H layer inside the sample matrix annealed for 200 h and only a small amount of residual 14H structure around the phase 18 R. For the as-extruded alloy, The introduction of 14H nuclei in the alloy has a large number of existence.At annealing, 18R structure continuously dissolved in the matrix until all disappeared, 14H layer with annealing time prolonging growth and thickening.When the 14H layer covers the substrate , Continue to extend the annealing time, the growth of the 14H ply is obstructed by the α-Mg grain boundaries, Coarsening and dissolution process occurs. In the as-extruded samples 200 h annealing, only 14H roughened structure.