【作者】 王建华；

【导师】 易丹青；

【作者基本信息】 中南大学 ， 材料学， 2003， 博士

【摘要】 本文采用不同熔铸工艺制备了12炉次的各种成分的2618合金；使用光学显微镜（OM）、扫描电镜（SEM）和透射电镜（TEM）观察了各种合金在不同状态下的显微组织；运用布氏硬度计、INSTRON拉伸试验仪和Gleeble-1500热模拟实验机等实验手段对这些合金的室温和高温力学性能及压缩蠕变性能进行了系统的研究。主要内容及结果如下： 形变热处理可使2618合金在时效处理后得到均匀、弥散的时效相，并使无沉淀析出带（PFZ）的宽度明显变窄；经过变形量为11～16％的形变热处理后，可使2618合金的室温抗拉强度提高10～17％，但塑性明显下降；采用形变热处理可以提高2618合金的耐热性能。 高铁、镍2618合金（2#）的铸态组织中出现粗大的针片状和块状的Al₉FeNi相，经热挤压后该相被破碎为较粗大的尖角状颗粒；增加铁、镍含量对合金的时效特性及时效后的硬度没有影响；将2618合金在较低的变形温度下，进行较大变形量的多向快速变形可以使粗大的Al₉FeNi相得到较好的破碎。 Al-Fe中间合金中粗大的Al₃Fe相和2618合金中粗大的Al₉FeNi相在该合金熔炼过程中具有组织遗传现象，当对高铁、镍2618合金熔体在960℃进行30min的高温过热处理后（3#），可基本消除这种组织遗传，并使该合金的高温和室温强度同时得到明显提高。 含锆的高铁、镍2618合金经熔体高温过热处理后（4#），在合金铸态组织中获得均匀细小的针片状Al₉FeNi相，热挤压后获得均匀细小的颗粒Al₉FeNi相；弥散Al₃Zr粒子的存在可使2618合金得到细小的再结晶晶粒组织，该合金既可获得较高的高温强度，还可获得较高的延伸率。含锆和锰的高铁、镍2618合金经熔体高温过热处理后（5#），也可使合金在热挤压后获得较细小的颗粒Al₉FeNi相，锰元素的存在使合金中的时效析出相（S’）细化，晶间无沉淀析出带宽度明显减小，使2618合金的室温和高温强度显著提高。 采用经过严重挤压变形的Al-5Wt％Ti中间合金，向2618合金中加入小于0.5Wt％的钛元素时（9#），能使2618合金的铸态晶粒组织明显细化，大量弥散的Al₃Ti颗粒强烈阻碍合金的再结晶及晶粒长大，使合金经热轧与淬火时效后的晶粒组织明显细化；钛元素的合金化明中南大学博士学位论文摘要显提高2618合金在250℃的高温瞬时强度和该合金在250℃经100小时高温热暴露后的高温瞬时强度。 采用经过高能球磨的复合溶剂与亚微米AIN颗粒的均匀混合物，经过搅拌铸造后，使得超细的AIN颗粒能均匀分布于2618合金中，使该合金合金（12#）热轧与淬火时效后的晶粒组织明显细化;超细AIN颗粒的引入明显提高2618合金在250℃的高温瞬时强度和该合金在250℃经100小时高温热暴露后的高温瞬时强度。 少量锡元素均匀分布于2618合金的铸态组织中，并细化2618合金的铸态晶粒组织和冷轧后的晶粒组织;锡元素降低2618合金在250℃的高温瞬时强度，但提高2618合金的室温抗拉强度，且对2618合金在250℃经100小时高温热暴露后的高温瞬时强度没有影响。 微量忆元素减少了2618合金中时效析出相的数量，使2618合金的室温强度、塑性和250℃的高温瞬时强度降低;忆元素使时效强化相S’相在高温热暴露时的长大速度减慢，而2618合金中难溶的含铭金属间化合物也有利于合金高温强度的提高，因此忆可提高2618合金在250℃经100h高温热暴露后的高温瞬时抗拉强度。 随着温度的升高，1#、3#和5#2618合金的蠕变应力指数都有明显的降低，而4#合金的蠕变应力指数变化不大。在引入门槛应力后，1#、3#、4#和5#2618合金的蠕变行为均可用微观结构不变模型得到满意解释，门槛应力可以用外推洲8一。曲线得到。 与l#合金相比、由于3#合金中增加了细小A19FeNi相的数量，使该合金在200℃和250℃时的门槛应力值分别增加了n MPa和12MPa，且蠕变速率降低，但其显态蠕变应力指数并不明显增加;对于4#合金，由于细小A19FeNi相和弥散A13Zr的强化作用及合金晶粒组织细化的影响，使其200℃时的门槛应力值降低了ZOMPa，250℃时的门槛应力值增加了53MPa，由于合金晶粒组织的细化，使该合金的蠕变速率与1#合金基本相当甚至更高;对于5#合金，由于时效相的细化、PFZ宽度的减小、合金中的细小A19FeNi相和弥散A13zr的共同强化作用，使其蠕变速率比l#合金低大约1个数量级，200’C和250℃时门槛应力值分别增加了26MPa和29MPa，但蠕变应力指数没有显著变化。更多还原

【Abstract】 Twelve kinds of alloy 2618 containing different percents of elements were prepared using different melt-treatment processes. The microstructures of these alloys at various states were evaluated using optical microscopy, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The room and elevated temperature mechanical properties as well as the compress creep properties of these alloys were studied systematically using Brinell hardness and INSRON tensile test apparatus as well as Gleeble-1500 heat simulating apparatus. The main contents and results are as follows:The precipitating phases with the characteristics of uniformity and dispersion could be obtained in alloy 2618 through thermo-mechanical aging treatment. The width of precipitate free zone in the alloy was decreased apparently. The room temperature tensile properties of the alloy increased by 10~17% and elongation decreased remarkably after thermo-mechanical aging treatment with 11-16% compress deformation. The heat-resistant properties of alloy 2618 could be improved using thermo-mechanical aging treatment.The coarse needle-like or nubby Al9FeNi phase existed in the cast microstructure of high content Fe and Ni alloy 2618(2#). After hot extrusion, it was broken into coarse multi-angle Al9FeNi particles. The contents of Fe and Ni have no effect on aging characteristic and the hardness of the alloy after aging. The coarse Al9FeNi phase in alloy 2618 could be broken better after the alloy was suffered larger quantity and high rate as well as multi-direction deformation at lower temperature.In the cast of alloy 2618, there existed structure inherits phenomena of coarse A^Fe and AlgFeNi phases, which were in Al-Fe master alloy and alloy 2618 respectively. The structure inherits could be eliminated when the alloy was over-heated at 960 癈 for about 30min. The elevated temperature and room temperature tensile properties of the alloy could be enhanced remarkably at the same time.After melt over-heat treatment, the uniformly and little needle-like Al9FeNi phase was obtained in the ingot of high content Fe and Ni alloy 2618 alloyed with zirconium (4#). The Al9FeNi phase was in the form of little particles after heat extrusion. Due to the retard effect of little Al3Zr particles to the recrystallization, the grain structure of alloy 2618 wasvery small. The elevated temperature tensile properties and elongation of the alloy could be enhanced apparently at one time. After melt over-heat treatment on high content Fe and Ni alloy 2618 alloyed with zirconium and manganese(5#), the small Al9FeNi particles were also obtained after it was heat extruded. The precipitate phases were smaller and the width of precipitate free zones(PFZ) in the alloy was narrower due to the effect of manganese. The room and elevated temperature tensile properties of the alloy were enhanced obviously at the same time.The Al3Ti particles in Al-5 Wt %Ti master alloy were small and uniformity after severely extrusion deformation. When the addition amount of titanium in the form of this master alloy was smaller than 0.5wt%, titanium made the grain structure of cast alloy 2618 very smaller. A large amount of dispersive Al3Ti particles retarded intensively the recrystallization and the grain growth of the alloy, so the grain size of the alloy after hot-extrusion and quench were smaller evidently. The alloying effect of titanium could increase remarkably the elevated temperature instantaneous tensile properties of the alloy at 250 C and that of the alloy which was exposed at 250C for 100 hours.The very little A1N particles were distributed evenly in alloy 2618 after stirring casting using intermixture of sub-micrometer A1N particles and complex solvent, which were mixed with high-energy ball mill. The grain sizes of the alloy (12#) after hot extrusion and quench aging were remarkably decreased due to the existence of these A1N particles. The addition A1N particles could increase remarkably the elevated temperature instantaneous tensile properties of the alloy at 250C更多还原