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研究了锻态Ni60Ti形状记忆合金在750~850℃的空气中的高温循环氧化行为,采用OM、XRD、SEM和EDS对氧化层的组织和物相进行分析。结果表明,随着氧化温度升高,合金氧化速度加快,氧化增重增大。在循环氧化前期(0~30h),氧化速度较快,反应级数n值均小于2;在循环氧化中后期(30~102h),750℃和800℃的n值大于2,而850℃时由于氧化层开裂、剥落,导致其n值(1.927)小于2。随着氧化温度升高和时间延长,由表及里,形成了4层结构的氧化层,依次为:TiO_2、TiO_2+NiTiO_3、TiO_2+NiTiO_3+Ni、Ni3Ti。
The cyclic oxidation behavior of as-formed Ni60Ti shape memory alloy at 750 ~ 850 ℃ was studied. The microstructure and phase of the oxide layer were analyzed by OM, XRD, SEM and EDS. The results show that with the increase of oxidation temperature, the oxidation rate of the alloy increases and the oxidation weight gain increases. In the early stage of cyclic oxidation (0 ~ 30h), the oxidation rate is faster and the reaction order n values are less than 2. In the middle and late stages of cyclic oxidation (30 ~ 102h), the n values at 750 ℃ and 800 ℃ are more than 2, As the oxide layer cracking, peeling, resulting in its n value (1.927) is less than 2. With the increase of the oxidation temperature and the prolongation of time, four layers of oxide layers were formed, which are: TiO_2, TiO_2 + NiTiO_3, TiO_2 + NiTiO_3 + Ni and Ni_3Ti.