热压致密化块体纳米晶Ag50Ni50合金的显微组织

Microstructure of bulk nanocrystalline Ag50Ni50 alloy prepared by hot pressing of mechanically alloyed powders

采用机械合金化 ,随后在 6 2 0℃ ,5 8MPa下热压制备了致密的块体亚稳态纳米晶Ag5 0Ni5 0合金 ,用X射线衍射仪、扫描电镜和透射电镜研究了其组织结构。晶格常数的精确测定结果表明 ,球磨 2 0 0h后Ag在Ni中固溶度为 4.96 %± 0 .2 1%(摩尔分数 ) ,Ni在Ag中固溶度为 0 .84%± 0 .30 %(摩尔分数 ) ,热压以后仍具有过饱和固溶度 ,Ag在Ni中为0 .45 %± 0 .11%(摩尔分数 ) ,在相近温度下稳定化处理后进一步脱溶。6 0 0～ 70 0℃时Ag在Ni中固溶度为 (0 .2 1～ 0 .2 4) %± 0 .11%(摩尔分数 ) ,Ni在Ag中固溶度小于 0 .1%(摩尔分数 )。机械合金化粉末的晶粒度约为 6nm ,热压后长大至 40～ 6 0nm ,退火后又长大至 10 0～ 110nm。

A bulk nanocrystalline Ag50Ni50 alloy has been prepared by hot pressing of mechanically alloyed powder at 620?℃ under a pressure of 58?MPa. The microstructural characteristics of the alloy were studied by X ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that after mechanical alloying for 200?h, a solid solubility of Ag in Ni reached 4.96%±0.21%(mole fraction) and Ni in Ag reached 0.84%±0.30%(mole fraction). After hot pressing, the Ag and Ni rich phases in the alloy were still in a state with certain degree of supersaturation, such as a solid solubility of Ag in Ni being 0.45%±0.11%(mole fraction). The results also reveal that the solubility of Ag in Ni is (0.21～0.24)%±0.11%(mole fraction) and that of Ni in Ag is less than 0.1%(mole fraction) at 600～700?℃. The grain size of the mechanically alloyed powders was about 6?nm. After hot pressing, it grew to 40～60 nm and then after annealing treatment it grew further to 100～110?nm. Furthermore, the influence of the variation of the grain size and the internal stress on the broadening of the X ray diffraction peaks was evaluated in detail and the role of the nanocrystalline structure in the fast densification process of the powders was also discussed.