机械合金化对热压合成Laves相NbCr_2合金1100℃氧化行为的影响

Effect of Mechanical Alloying on Oxidation Behavior at 1100 ℃ of Laves Phase NbCr_2 Alloys by Hot Pressing Synthesis

采用机械合金化+热压烧结工艺制备Laves相NbCr2合金,研究球磨时间对热压合金晶粒尺寸及致密度的影响,探讨了晶粒细化对其1100℃氧化行为影响的作用机制。结果表明,随着Cr-Nb粉末球磨时间的延长,热压合金组织越来越致密,晶粒尺寸越来越小。当球磨时间达到100h时,NbCr2合金的相对致密度及晶粒尺寸分别达到98.7%和35nm。晶粒的细化有利于Cr原子扩散能力的提高,促进了Cr2O3膜的形成;但晶粒过细时,导致氧化膜内生长应力的增加,引起氧化膜的开裂、脱落,从而加剧了氧化。

Laves phase NbCr2 alloys were prepared by mechanical alloying and hot pressing sintering technology. Influences of the milling time on the grain size and density of the hot-pressed alloys were studied. The effect mechanism of grain refinement on 1100 ℃ oxidation behavior was also discussed. Results show that the relative density of the hot-pressed alloys increased and the grain size decreased when the milling time of Cr-Nb powders was prolonged. When the milling time was 100 h, the relative density and the grain size reached 98.7% and 35 nm, respectively. The grain refinement was beneficial to the improvement of Cr atom dispersion to form Cr2O3 film. However, the excessive refinement of grains resulted in the growth stress increase of the oxides film and then the oxide films cracked and shed; as a result, the oxidation was exacerbated.