论文部分内容阅读
通过高温Ｘ射线衍射仪研究了 Ｃｕ－１２％Ａｌ（质量分数，下同）合金熔体结构，并用纯铜作对比实验．在１２５０℃时，发现 Ｃｕ－１２％Ａｌ合金熔体结构因子曲线上１８．５ｎｍ－１位置有预峰出现．随着温度的下降，预峰变得更加明锐．预峰的出现是液体中存在中程有序的标志．通过熔态旋淬法获得该合金的快速凝固条带，对条带进行固态Ｘ射线衍射分析，其结构是具有有序体心立方晶格的Ｃｕ３Ａｌ．熔体内的中程有序结构单元尺寸与快凝Ｃｕ３Ａｌ（１１１）晶面面间距ｄ１１１数值一致．由双体分布函数得到的最近邻原子距离、配位数 结合原子团簇结构单元的几何模型，计算得出该体心立方的棱边长（ａ＝３．００ × １０－１０ｍ）与文献中所提供的固态晶格常数（ａ＝２．９５ × １０－１０ｍ）基本吻合．可证明该合金熔体中存在以ＤＯ３结构为基本单元的中程有序原子团簇，在液相线以上２００℃温度范围内这种中程有序都能稳定存在，并随着温度的下降，中程有序的相关尺寸逐渐增大．
The melt structure of Cu-12% Al (mass fraction, the same below) alloy was studied by high-temperature X-ray diffractometer and compared with pure copper. At 1250 ℃, it was found that the Cu-12% Al alloy melt structure factor curve at 18.5nm-1 pre-peak position appears. As the temperature drops, the pre-peak becomes more sharp. The appearance of pre-peak is a medium-range order in the liquid. The rapidly solidified ribbons of the alloy were obtained by the melt-spinning method. The ribbons were analyzed by solid-state X-ray diffraction and the structure was Cu3Al with ordered body-centered cubic lattice. Melt in the mid-range orderly structure unit size and rapid solidification Cu3Al (111) crystal surface spacing d111 consistent. According to the nearest neighbor distance and coordination number obtained from the bilayer distribution function, the edge length (a = 3.00 × 10 -10 m) of the body-centered cubic is calculated according to the geometric model of the atomic cluster. The solid state lattice constant provided (a = 2.95 × 10-10m) basically coincide. It can be proved that there exists a mesophase ordered atomic cluster with DO3 structure as the basic unit in this alloy melt. This mid-range order exists stably in the temperature range of 200 ℃ above the liquidus, and as the temperature decreases, Mid-range orderly related size gradually increased.