界面能調(diào)控納米顆粒在熔體中分布反應(yīng)合成制備鐵基ODS合金

界面能調(diào)控納米顆粒在熔體中分布反應(yīng)合成制備鐵基ODS合金EFFECT OF INTERFACIAL ENERGY ON DISRIBUTION OF NANOPARTICLE IN THE MELT DURING THE PREPARATION OF Fe-BASED ODS ALLOYS BY THERMITE REACTION

鐵基ODS合金(oxide dispersion strengthened, ODS)通常用機(jī)械合金化工藝制備，氧化物表面易污染且制造成本高是制約其發(fā)展的主要瓶頸。本課題利用鋁熱合成結(jié)合快速凝固技術(shù)制備了鐵基ODS合金。經(jīng)過優(yōu)化鋁熱劑成分，合金熔體中不僅原位生成了α-Al2O3納米顆粒，還發(fā)生了液相調(diào)幅分解形成了富Fe、Cr與富Ni、Al的兩相結(jié)構(gòu)。因為α-Al2O3與富Ni、Al相之間的界面能較低，Al2O3納米顆粒與富Ni、Al相結(jié)合從而在基體中均勻分布。本文分析了反應(yīng)熔體發(fā)生液相調(diào)幅分解的熱力學(xué)可能性以及納米顆粒在界面能和布朗運動影響下的移動速率。實驗結(jié)果表明，液相調(diào)幅分解得到的NiAl相呈球形，直徑約50nm，體積分?jǐn)?shù)約50%；反應(yīng)合成的α-Al2O3顆粒直徑約5nm，受界面能作用全部與NiAl相結(jié)合。計算表明，受界面能和布朗運動影響α-Al2O3顆粒移動速率極快，快速冷卻過程中完全有時間在兩相液體間完成移動和分布。測試表明，鐵基ODS合金平均拉伸強(qiáng)度為602 MPa，延伸率為21%，大氣環(huán)境下1000℃下氧化100h后增重0.4mg/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 paper 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 50nm, whose volume fraction reaches up to 50%; and nanoparticle α-Al2O3, formed during thermite reaction, has a diameter of 5nm 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 602MPa with ultimate elongation of 21% and its mass gain under 1000℃ in air for 100h is 0.4mg/cm2.

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