摘要
结合Thermo-Calc热模拟程序计算和实验(电子显微镜、微探针分析和X射线衍射)研究四元系Al-(24)Ca-Ni-La(质量分数,%)合金在铝角附近的结构。根据得到的相平衡数据,提出Al-Ca-Ni-La体系液相面和固相相场分布的实验投影。显微组织研究表明,含2%4%Ca、2%4%Ni和1%3%La(质量分数)的合金具有超细的亚共晶组织,共晶金属间化合物的体积分数为30%,因此,可以将这些合金归类为天然Al基复合材料。超细共晶结构产生显著的强化作用,其机制可以很好地用修订的Orowan循环模型描述。在350400℃退火过程中,由于L12型相(Al3(Zr,Sc))纳米颗粒的形成,添加少量的Zr和Sc(分别为0.2%和0.1%,质量分数)具有显著的强化作用(提高约25%)。由于共晶金属间化合物的体积分数高,该新合金具有低的热膨胀系数、高的结构热稳定性和力学性能。
The structure of the quaternary Al?(2?4)wt.%Ca?Ni?La system near the aluminum corner has been studied using computational analysis in the Thermo-Calc program and experimental studies(electron microscopy,microprobe analysis and X-ray diffraction).Based on the phase equilibria data obtained,the experimental projection of the liquidus surface and solid state phase-field distribution of the Al?Ca?Ni?La system have been proposed.Microstructure studies reveal that the alloys with the 2?4 wt.%Ca,2?4 wt.%Ni and 1?3 wt.%La ranges have an ultra-fine hypoeutectic structure with 30%volume fraction of eutectic intermetallics,which allows one to classify these alloys as natural Al-matrix composites.The ultra-fine eutectic structure produces significant strengthening,the magnitude of which can be well described using the modified Orowan looping mechanism model.Small additives of Zr and Sc(0.2 and 0.1 wt.%,respectively)lead to significant strengthening(by^25%)due to the formation of L12 type phase(Al3(Zr,Sc))nanoparticles during annealing of the alloy at 350?400℃.Due to the high volume fraction of eutectic intermetallics,the new alloys have low coefficients of thermal expansion and high thermal stability of the structure and mechanical properties.
基金
financial support of the grant of the Russian Science Foundation(Project No.18-79-00345)(preparation of alloys,electron microscopy(SEM,EMPA,TEM),tensile tests)
Ministry of Science and Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of MISiS(No.P02-2017-2-10)(thermodynamic calculations,dilatometry,DSC and XRD).
