【作者】 陈冰；

【导师】 王翠萍；

【作者基本信息】 厦门大学 ， 材料工程， 2017， 硕士

【摘要】 目前,铁基高温合金已经成为国防、能源、航空以及核工业等领域广泛应用的主要高温材料之一。相图是材料设计的基础,对新材料的研发具有十分重要的指导意义。本研究采用实验研究与热力学计算相结合的方法对部分铁基高温合金三元系相图进行了研究,主要研究结果如下:（1）本研究采用合金法、电子探针显微分析仪（EPMA）和X射线衍射（XRD）技术,测定了 Fe-Mo-Nb三元系在1000℃、1200℃以及1300℃的等温截面相图。实验结果表明,具有相同D85晶体结构的μFe₇Nb₆和μFe₇Mo₆相并未形成连续的固溶体化合物相,出现了 BCC（Mo,Nb）+μFe₇Nb₆+εFe₂Nb,BCC（Fe）+εFe₂Nb+μFe₇Mo₆ 和 BCC（Mo,Nb）+εFe₂Nb+μFe₇Mo₆ 三相平衡。结合文献报道,以本研究的实验结果为依据,采用CALPHAD方法计算了该三元系的相图,计算结果与实验结果取得较好的一致性。（2）采用合金法、电子探针显微分析仪（EPMA）和X射线衍射（XRD）技术,对Fe-Ta-Nb三元系在1100℃、1200℃和1300℃时的等温截面相图进行了实验测定。实验结果表明,具有相同C14晶体结构的εFe₂Nb和εFe₂Ta相形成了连续的εFe₂（Nb,Ta）化合物相;同时具有相同D85晶体结构的μFe₇Nb₆和μFe₇Ta₆相形成了连续的μFe₇（Nb,Ta）6固溶体化合物相。基于本研究的实验结果,通过CALPHAD方法计算了 Fe-Ta-Nb三元系相图,获得了自洽性良好的热力学参数。（3）采用合金法、电子探针显微分析仪（EPMA）和X射线衍射（XRD）技术,测定了 Cr-Mo-Nb三元系在1000℃和1200℃时的等温截面相图。在1000℃和1200℃的实验结果中均出现BCC₁+BCC₂的两相分离区。结合本研究的实验结果和相关的实验报道,利用CALPHAD方法优化与计算了该三元系的相图,同时计算了 Nb元素的添加对Cr-Mo二元系中BCC相的两相分离的影响,结果表明Nb元素使Cr-Mo二元系中BCC相的两相分离温度明显提高。更多还原

【Abstract】 Iron-based superalloys are widely used in the field of high-temperature applications like components for jet engines and gas turbines,including blades,disks,rotors,and combustor/burner cans,as well as compressor and turbine cases.Phase diagram is the basis of material design,which has a significance guide to the research and development of the new material.In this work,phase equilibria of part Iron-based superalloys ternary systems were studied using a combined method of experimentally determined and thermodynamic assessment.Major contents are listed below:（1）the phase equilibria of the Fe-Mo-Nb ternary system at 1000℃,1200 ℃ and 1300℃ were experimentally determined using a combined method of electron probe microanalysis and X-ray diffraction on the equilibrated alloys.The obtained experimental results show that the existences of several three-phase equilibria（i.e.,BCC（Mo,Nb）+μFe₇Nb₆+εFe₂Nb,BCC（Fe）+εFe₂Nb+μFe₇Mo₆ and BCC（Mo,Nb）+εFe₂Nb+μFe₇Mo₆）are identified in all studied isothermal sections.Based on the experimental data,the phase equilibria of Fe-Mo-Nb ternary system were also thermodynamically optimized using CALPHAD method.And the calculated results are in good agreement with the experimental investigations in the Fe-Mo-Nb ternary system.（2）the phase equilibria of the Fe-Ta-Nb ternary system at 1100 ℃,1200 ℃ and 1300℃ were experimentally determined.The investigations lead to following conclusions:（1）the μFe₇Ta₆ andμFe₇Nb₆ phases form a μFe₇（Ta,Nb）6 monophase;（2）the laves εFe₂Ta and εFe₂Nb phases also form a εFe₂（Ta,Nb）monophase in the current work.A consistent thermodynamic data set for Fe-Ta-Nb ternary system was obtained using CALPHAD method.And the calculated phase diagrams are in satisfactory agreement with the experimental investigations of the Fe-Ta-Nb ternary system in this work.（3）In the present work,the phase equilibria of the Cr-Mo-Nb ternary system at 1000 ℃ and 1200 ℃ were experimentally determined using a combined method of electron probe microanalysis and X-ray diffraction on the equilibrated alloys.The existence of three-phase equilibria BCC₁+BCC₂+Cr₂Nb is identified in all studied isothermal sections.Based on the experimental data of phase equilibria,the Cr-Mo-Nb ternary system was also thermodynamically optimized using the CALPHAD method.The BCC phase separation of the Cr-Mo system with different Nb additions also was calculted,which is in good agreement with the experimental investigations in the Cr-Mo-Nb ternary system.更多还原