Fe2O3对氧化物弥散强化Fe12CrWTiY合金的显微组织和高温拉伸性能的影响

采用气体雾化Fe-12Cr-2.5W-0.4Ti-0.25Y合金粉末,添加1%(质量分数)的Fe2O3作为携氧剂,制备氧化物弥散强化Fe-12Cr-2.5W-0.4Ti-0.25Y高温合金。测定该合金在室温以及550~850℃的高温抗拉强度,采用X射线衍射仪分析合金的物相组成,通过扫描电镜和透射电镜观察合金的组织和拉伸断口形貌。结果表明,添加Fe2O3后,合金晶粒细化,平均晶粒尺寸由8.6μm减小到7.3μm。基体中第二相除纳米尺寸的Ti2Y2O7外,还形成20~200nm和1~10μm两种尺度的Y3Fe5O12、Cr1.3Fe0.7O3和(Cr0.88Ti0.12)2O3等多种复合氧化物,以及宽度分别为200~300nm和5~30 nm的板条组织,室温、550℃和850℃下的抗拉强度分别为1 257、1 108、和128 MPa,比未添加Fe2O3的合金分别提高50.7%,39%和30.6%。添加Fe2O3增加了氧化物的数量,提高了弥散强化效果,但微米尺度氧化物第二相的膨胀系数与基体不同,在高温下与基体的界面产生分离,优先形成裂纹源,降低高温强化效果。

Effect of Fe2O3 additive on microstructure and high temperature tensile properties of oxide dispersion-strengthened Fe12CrWTiY alloys

Oxide dispersion-strengthened(ODS) Fe-12Cr-2.5W-0.4Ti-0.25Y(mass fraction,%) alloys were fabricated by gas-atomized prealloy powders with 1% Fe2O3additive as the oxygen carrier.High temperature tensile properties,phase composition,microstructure and fracture morphology of the alloys with and without Fe2O3 additive were studied.Experimental results show that the addition of Fe2O3refines the average grain size of the prepared alloys from 8.6 μm to 7.3 μm.In addition to the nanoscale Ti2Y2O7second phase,there also exist several other kinds of complex oxide particles in the matrixes,including Y3Fe5O12,Cr1.3Fe0.7O3 and(Cr0.88Ti0.12)2O3 with sizes of 20~200 nm and 1~10 μm,along with lath-like structures with width of 200~300 nm and 5~30 nm.The tensile strength of the alloy was estimated to be 1257,1108 and 128 MPa at room temperature,550 and 850 ℃,respectively,increased by 50.7%,39% and 30.6% compared with the alloy without Fe2O3 additive.Addition of Fe2O3 can improve the dispersion strengthening effect by increasing the number of dispersive oxides in the alloys.However,upon high temperature,micro-scale oxide particles were observed to separate from the alloy matrix probably owing to their different expansion coefficients,leading to preferential crack formation and thus deteriorated high-temperature tensile properties.