纳米晶Ni-Ag合金高温氧化行为研究

OXIDATION BEHAVIOR OF NANOCYSTALINE Ni-Ag ALLOYS

球磨 8 0～ 2 0 0h的Ni-Ag合金粉末经热压烧结后获得了晶粒尺寸小于 5 0nm的Ni- 5 0Ag纳米晶块体材料 ,经热处理后其晶粒长大约至 10 0nm .在 6 0 0℃的高温氧化时 ,合金呈现出不同的氧化膜结构及氧化增重速率 .MA 80hNi- 5 0Ag和MA 2 0 0hNi- 5 0Ag合金在 6 0 0℃空气氧化时均未形成选择性的外氧化膜 ,而形成了非平衡态复杂内氧化结构 .热处理前 ,合金的氧化行为受晶粒尺寸以及合金内部缺陷 ,内应力等诸多因素的影响 ,导致MA80h和 2 0 0h合金不同时间合金氧化速率常数相差较大 .而经热处理后 。

Two Ni-Ag alloys, containing Ni of 50 at %, denoted as MA 80hr Ni-50Ag and MA 200hr Ni-50Ag were consolidated with hot pressing (HP) process after mechanical alloying (MA) for 80 hr and 200 hr respectively. The grain size of the as-made alloys was less then 50 nm and that of the alloys after annealing treatment increased to near 100 nm. The nanocrystalline alloys were oxidized in air at 600℃ for 24 hr. The alloys undergo an internal oxidation of nickel associated with the formation of an outermost layer of silver metal.The oxidation rates of the two as-made alloys had a considerable disparity,but which became smaller after annealing treatment performed.