FeCrNiAl系高熵合金高温氧化行为及组织演变研究

Oxidation Behaviors of FeCrNiAl High Entropy Alloy and Its Microstructure Evolution

研究了FeCrNiAl系高熵合金的高温氧化行为,建立了合金的氧化动力学模型,同时借助XRD、SEM和能谱分析,对合金氧化物相结构及形貌和成分进行表征,分析了合金的氧化机理。结果表明合金在800~1000℃都是完全抗氧化的,随着氧化温度的提高,合金氧化速率先增加后减小,1000℃的平均氧化速率小于800℃的平均氧化速率;各个温度下试样单位面积的氧化增重与氧化时间的关系满足抛物线规律,计算得到合金的氧化激活能为167.507 kJ/mol;800℃下枝晶内的氧化产物全部是棒状的金红石结构TiO_2,而枝晶间氧化产物则主要是片层状、紧密相连的Cr_2O_3和TiO_2;900和950℃下形成的氧化膜中主要氧化物均为TiO_2,900℃还含有Cr_2O_3和Fe2O3,950℃氧化膜中还含有α-Al_2O_3。在1000℃合金表面仅形成致密的α-Al_2O_3薄膜,使合金表现出更为优异的抗氧化性能。

The oxidation behaviors of FeCrNiAl high entropy alloy at high temperature were investigated,and the oxidation kinetics model was constructed.The phase structure,morphology and composition of the alloy were characterized by XRD,SEM and EDS,and the oxidation mechanisms were analyzed.The results show that the alloy is fully oxidation-resistant at 800~1000 ℃.The average oxidation rate in 100 h increases with increasing temperature at first and then decreases;it at 1000 ℃ is smaller than the one at 800 ℃.The relationship between mass increment and oxidation time for all temperatures meets the parabola function,and the oxidation active energy is calculated to be 167.507 kJ/mol.The oxidation products in dendrite at 800 ℃ are bar-shaped TiO2 with rutile structure,while the interdendritic products are Cr2O3 and TiO2 which is plate shaped.The oxidation products at 900 ℃ are TiO2,Cr2O3 and Fe2O3,while TiO2 and α-Al2O3 at 950 ℃ are observed.Only tight α-Al2O3 film is obtained on the surface at 1000 ℃,which results in excellent oxidation resistance.