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利用θ θ液态金属X射线衍射仪 ,研究了 6 75℃时Al_1 1 %Fe(质量分数 ,下同 )合金的熔体结构及其与熔体热历史的关系 ,并用纯铝作对比研究 .结果表明 ,未过热铝铁合金熔体的结构因子的小角部分出现预峰 ,高温过热后预峰消失 ;而纯铝熔体的结构因子在过热前后基本不变 ,也未出现预峰 .预峰的出现是液体中存在中程序的标志 ,预峰直接对应于Fe_Fe原子在中程序尺度上的关联 .以晶体结构作为一级近似 ,就可以构造一个液体结构模型 .基本的单元是一个体心立方 ,8个Al原子位于它的顶点上 ,一个Fe原子占据它的中心 .这样的单元沿着体对角线方向平移一个对角线的距离 ,能够满足预峰对Fe_Fe原子间距的要求 ,并给出一个类DO3 结构 .再将单元之间的空隙用铝的类fcc晶胞填充 ,那么整个实体的成分约为Al7Fe ,与由快速凝固所得的亚稳相Al6Fe的成分相近 .可以推测在液体亚共晶铝铁合金中存在成分近似Al6Fe的原子团簇
The relationship between melt structure and melt thermal history of Al 1 1% Fe (mass fraction) at 6 75 ℃ was studied by using θ θ liquid metal X-ray diffractometer. The results were compared with pure aluminum It is indicated that the pre-peak appears at the small corner of the structure factor of unheated Al-Fe alloy and disappears after overheating at high temperature, while the structure factor of Al-melt does not change or appears pre-peak before and after overheating. Is a sign of the existence of a medium in the liquid and the pre-peak corresponds directly to the association of the Fe-Fe atoms in the middle scale. A liquid structure model can be constructed using the crystal structure as a first approximation. The basic unit is a body-centered cubic One Al atom is located on its apex and one Fe atom occupies its center. Such a unit translates a diagonal distance along the body diagonal to meet the pre-peak requirement for Fe-Fe atomic spacing and gives a Type DO3 structure. And then the gap between the cells filled with aluminum fcc unit cell, then the composition of the entire entity is about Al7Fe, and by the fast solidification of the composition of the metastable phase Al6Fe similar to presumably in the liquid Component is present in approximately Al6Fe eutectic aluminum-iron the Clusters