(西北工業(yè)大學(xué) 凝固技術(shù)國家重點(diǎn)實(shí)驗(yàn)室，西安 710072)
摘 要: 采用機(jī)械球磨方法制備了Fe-1%C(摩爾分?jǐn)?shù))單相固溶體納米晶粉體材料，通過掃描電鏡(SEM)及X射線衍射儀(XRD)分析球磨時(shí)間對(duì)粉末形貌和晶粒尺寸的影響，應(yīng)用Scherrer公式得出平均晶粒尺寸與球磨時(shí)間的關(guān)系。結(jié)果表明：在球磨機(jī)主轉(zhuǎn)速為155 r/min條件下，球磨10 h時(shí)，得到Fe-C單相固溶體；球磨時(shí)間達(dá)到85 h以上時(shí)，合金粉末形貌及尺寸趨于穩(wěn)定，晶粒尺寸穩(wěn)定在8 nm左右。由于大量晶界以及微觀應(yīng)變的存在，獲得的Fe-C納米晶具有自發(fā)長大趨勢。采用差熱分析(DSC)手段研究不同等溫條件下Fe-C納米晶的熱穩(wěn)定性，結(jié)合晶粒長大熱力學(xué)和動(dòng)力學(xué)理論，求得晶界擴(kuò)散激活能及穩(wěn)定晶粒尺寸等參數(shù)，并分析討論Fe-C納米晶的晶粒穩(wěn)定機(jī)制。
關(guān)鍵字: Fe-C合金；納米晶；穩(wěn)定性；機(jī)械球磨
mechanical milling and its thermal stability
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:The particles of Fe-1%C (mole fraction) alloy with the single phase solid solution nanocrystalline were produced by mechanical milling. The influences of milling time on the particles morphologies and the grain size were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Applying Scherrer formula, the average grain size, furthermore, the grain size evolution with the milling time, was obtained. The results show that the single phase solid solution has already been achieved after 10 h milling. Both the particles morphologies and the grain size become stable after milling over 85 h, and the final grain size is about 8 nm. The Fe-C nanocrystallines have the tendency of growing up resulting in the large amount of grain boundaries and micro-strain among them. The thermal stability of Fe-C nanocrystalline at different temperatures was investigated by isothermal differential scanning calorimetry (DSC) technology. Combining with the thermodynamics and kinetics of grain growth, the active energy of grain boundary diffusion and the stable grain size were calculated, and the stable mechanism of Fe-C nanocrystalline was discussed.
Key words: Fe-C alloy; nanocrystalline; thermal stability; mechanical milling
