利用铝热合成工艺结合快速凝固技术制备了铁基氧化物弥散强化(ODS)合金。经过优化铝热剂成分,合金熔体中不仅原位生成了α-Al2O3纳米颗粒,还发生了液相调幅分解,形成了富Fe、Cr与富Ni、Al的两相结构。因为α-Al2O3与富Ni、Al相之间的界面能较低,Al2O3纳米颗粒与富Ni、Al相结合,从而在基体中均匀分布。分析了反应熔体发生液相调幅分解的热力学可能性以及纳米颗粒在界面能和Brownian运动影响下的移动速率。实验结果表明,液相调幅分解得到的NiAl相呈球形,直径约50 nm,体积分数约50%;反应合成的α-Al2O3颗粒直径约5 nm,受界面能作用全部与NiAl相结合。计算表明,受界面能和Brownian运动影响,α-Al2O3颗粒移动速率极快,快速冷却过程中完全有时间在两相液体间完成移动和分布。测试表明,铁基ODS合金平均拉伸强度为602 MPa,延伸率为21%,大气环境中1000 ℃下氧化100 h后增重0.4 mg/cm2。
Fe-based oxide dispersion strengthened (ODS) alloys are conventionally manufactured through mechanical alloying. Such route even involves an expensive milling step but the oxide surface still could not avoid being contaminated. This work developed a new method by combination of thermite reaction and rapid solidification (RS) to prepare ODS alloys. Attributing to the optimization of thermite mixture composition, nanoparticle α-Al2O3 was synthetized in situ and the molten alloy was modulated by spinodal decomposition (SD) into Fe, Cr-rich and Ni, Al-rich regions. During the cooling of the melt, the low interfacial energy between α-Al2O3 and Ni, Al-rich region was also considered in the process for nanoparticles α-Al2O3 to assemble into NiAl, thus they could uniformly distribute in matrix. This work focuses on the thermodynamic analysis of SD in the melt alloy and the speed of the nanoparticles α-Al2O3 under the influence of interfacial energy and Brownian motion. Experiment results shows that the spherical NiAl segregated by SD has a mean diameter of about 50 nm, whose volume fraction reaches up to 50%; and nanoparticle α-Al2O3, formed during thermite reaction, has a diameter of 5 nm combined into NiAl under the influence of interfacial energy. Computation results indicate that, driven by interfacial energy and Brownian motion, nanoparticle α-Al2O3 could move fast enough into Ni, Al-rich region before solidification accomplishes during RS. Test results imply that the tensile strength of Fe-based ODS alloy is 602 MPa with ultimate elongation of 21% and its mass gain under 1000 ℃ in air for 100 h is 0.4 mg/cm2.
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