(西北工業(yè)大學 凝固技術(shù)國家重點實驗室，西安 710072)
摘 要: 采用三元微觀相場動力學模型研究Ni75MnxAl25−x合金早期沉淀相的形成過程。對合金微觀組織演化圖像、有序相體積分數(shù)曲線、序參數(shù)曲線及占位幾率的分析表明：該合金首先析出L10結(jié)構(gòu)，隨后L10結(jié)構(gòu)向L12結(jié)構(gòu)轉(zhuǎn)變，L12結(jié)構(gòu)在L10結(jié)構(gòu)的內(nèi)部析出。隨著Al濃度的增大，等成分有序化階段縮短；且L10結(jié)構(gòu)體積分數(shù)增大，發(fā)生結(jié)構(gòu)轉(zhuǎn)變的時間提前。Al和Mn原子在(001)和(002)面幾乎同時有序排列，但是一定時間后(002)面原子開始貧化，發(fā)生結(jié)構(gòu)轉(zhuǎn)變，Al原子主要占據(jù)b 位，Mn原子主要占據(jù)aⅡ位。合金最終析出單一的L12偽二元結(jié)構(gòu)。
關(guān)鍵字: Ni75MnxAl25−x合金；微觀相場；序參數(shù)；L10早期沉淀相
pre-precipitation phase in Ni75Al25−xMnx alloy
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:The microscopic phase-field model was used to simulate the formation of pre-precipitation phase in Ni75Al25−xMnx alloy. The results of the microscopic morphology evolution of alloys, the volume fraction curves, order parameter curves and occupation probability show that L10 phase precipitates from the Ni75Al25−xMnx alloy first and then transforms into L12 phase inside of L10 phase in the following time. With the increase of Al concentration, the nucleation incubation periods of L10 and L12 phases and structure transformation time obviously become shorter. The ordering of Al and Mn atoms takes place in (001) and (002) planes simultaneously. As followed, the atom order degree begins to decrease in (002) planes and the structure is changed. Al atoms preferentially occupy the β site and Mn atoms preferentially occupy the aⅡ site. Finally, the L10 pseudobinary structure precipitates in the alloy system.
Key words: Ni75MnxAl25−x alloy; microscopic phase-field; order parameter; L10 pre-precipitation phase
