晶粒尺寸对含Zr的Ni_3Al合金氧化行为的影响

EFFECT OF GRAIN SIZE ON OXIDATION BEHAVIOUR OF Ni_3Al-Zr BASE ALLOY AT ELEVATED TEMPERATURE

研究了Ｎｉ－１１，８２Ａｌ－１．０３Ｚｒ－０．１Ｂ（ｗｔ－％）合金晶粒尺寸为３０和１８０μｍ两种组织结构试样，在９００和１１００℃静态空气中的等温氧化行为．发现，当氧化温度为９００℃时，氧化速率随晶粒尺寸减小而减小，而在１１００℃，二者氧化速率几乎没有区别．利用ＥＰＭＡ，ＸＲＤ分析了氧化产物，证明两种试样的氧化膜相成分与结构，均由ＮｉＯ外层和Ａｌ_２Ｏ_３，ＮｉＡｌ_２Ｏ_４内层组成．但氧化膜／合金界面形貌显著不同．９００℃氧化膜与合金界面呈平滑的波浪型，而１１００℃界面出现树根状突出氧化物伸入到合金表层内部．对上述实验结果作了理论分析，认为前一结果为合金晶界快速短路扩散传质所致、而后一现象与合金晶粒尺寸关系较小，起决定作用的为活性元素Ｚｒ的“反应元素效应（ＲＥＥ）”．

The oxidation behaviour of Ni-11.82Al-1.03Zr-0.1B(wt-%) alloy with grain sizes of 30 μm and 180 μm was investigated at 900, 1100℃ in air. The short-circuit path for rapid diffusion along grain boundary is responsible for the change in the oxidation rate. At 900℃.with decreasing grain size.the oxidation rate of Ni-11.82Al-1.03Zr-0.1B alloy lowered; at 1100℃, grain size did not affect it. The structure and composition of the oxide scale were examined by EPMA and XRD analyses. which confirmed that the oxide layers formed on the two specimens are the same, containing NiO(outer), Al_2O_3, NiAl_2O_4(inner). The reactive element effect of Zr caused that the scale-alloy interface distinctly showed a different shape. a wavy interface(900℃) and a tree-like interface(1100℃).