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(1)成功制备出了增强相Al_3Ti尺寸小于0.5μm、AlN的尺寸达到纳米的AlN.Al_3Ti/ZL101原位复合材料。增强相Al_3T_i的尺寸大小取决于制备工艺及合金液中T_1元素的扩散速度。Al_3Ti晶核形成后对其周围溶质的吸附作用满足Langmuir吸附理论。吸附的溶质阻碍了Ti元素的扩散,使Al_3Ti晶核形成后很难长大而能大量形核,并保持亚微米级尺寸。采用X射线衍射及TEM方法分析并确定了增强相Al_3Ti和AlN。(2)二水平七因素及三水平四因素正交实验确定了AlN.Al_3Ti/ZL101原位复合材料的最佳成分。该原位复位材料的最大拉伸强度为360MPa、布氏硬度为122、弹性模量达到92GPa、延伸率为3.8％。(3)原位复合材料晶粒尺寸较基体细小得多。Al_3Ti可显著细化α-Al晶粒,α-Al晶粒的细化使其周围的共晶硅细化;AlN相存在于共晶硅中,作为异质晶核可显著细化共晶硅。TEM分析表明,基体和增强相Al_3Ti之间存在一定的晶体学位向关系并出现共格现象。原位复合材料的主要强化机制为细化晶粒强化(细化α-Al晶粒、细化和粒化共晶硅晶粒、细化AlN晶粒和细化Al_3Ti晶粒)、弥散强化和复合强化。(4)首次研究了原位复合材料的铸造性能和重复使用性能。在铝合金铸件的正常浇注温度下,AlN.Al_3Ti/ZL101原位复合材料有较基体ZL101更好的流动性、更小的
(1) The AlN.Al_3Ti / ZL101 in-situ composites with Al_3Ti size less than 0.5μm and AlN size up to nanometer were prepared successfully. The size of Al_3T_i reinforced phase depends on the preparation process and the diffusion rate of T_1 in the alloy liquid. The adsorption of solutes around Al 3 Ti crystal nuclei satisfies the Langmuir adsorption theory. Adsorbed solutes impede the diffusion of Ti elements, Al 3 Ti after the formation of nuclei is very difficult to grow up to a large number of nucleation, and maintain sub-micron size. XRD and TEM methods were used to analyze the Al 3 Ti and AlN phases. (2) The best composition of AlN.Al_3Ti / ZL101 in-situ composites was determined by two-level seven-factor and three-level four-factor orthogonal experiment. The in situ reduction material has a maximum tensile strength of 360 MPa, a Brinell hardness of 122, an elastic modulus of 92 GPa and an elongation of 3.8%. (3) In-situ composite grain size much smaller than the matrix. Al_3Ti can significantly refine the α-Al grains. The refinement of α-Al grains refine the eutectic silicon around it. The AlN phase exists in the eutectic silicon, which can remarkably refine the eutectic silicon . TEM analysis shows that there is a certain crystal orientation relationship between Al 3 Ti and the matrix and the coherent phenomenon. The main strengthening mechanism of the in-situ composites is to refine the grain strengthening (refine the α-Al grains, refine and granulate the eutectic silicon grains, refine the AlN grains and refine the Al_3Ti grains), dispersion strengthening and Compound strengthening. (4) For the first time, the castability and reusability of in-situ composites were studied. AlN.Al_3Ti / ZL101 in-situ composites have better fluidity than matrix ZL101 at the normal pouring temperature of aluminum alloy castings, and smaller