【作者】 王超；

【导师】 袁守谦；

【作者基本信息】 西安建筑科技大学 ， 材料学， 2013， 博士

【摘要】 高强度低膨胀合金(High Strength Low Thermal Expansion, HSLTE)克服了传统Fe-Ni低膨胀合金强度较低的问题而具有较高的强度和低的膨胀系数，使其应用得到扩展。如何兼顾这两种性能，把功能材料作为特殊结构材料使用，成为研究者所关注的研究方向。本课题研究以金属膨胀相关理论和细晶强化为主的综合强化方法为基础，选择具有细化晶粒作用的顺磁性合金元素，结合Factsage热力学软件计算的Fe-Ni-X相图，研究控制Fe-Ni因瓦合金线膨胀系数、合金的强度和组织稳定性相匹配的关键环节，提高合金性能。实验研究是通过全程气氛保护熔炼、锻打成型以及热处理等工艺制备试样，在对试样膨胀性能、显微硬度以及组织检测、XRD衍射物相分析的基础上，研究对因瓦合金性能影响的因素，为制定合理的熔炼工艺和强化处理路线提供基础支持。(1)对基体平均线膨胀系数的影响，单元素的次序为W、Nb和Mo，合金化后试样的平均线膨胀系数相对于未合金化试样分别提高的幅度约50%、50%和110%左右；二元合金W+Mo和W+Nb合金化后试样的平均线膨胀系数相对于未合金化试样提高了62.5%，而Mo+Nb对基体的平均线膨胀系数的影响就相对较大，增加了125%。除Mo和Mo+Nb合金化的平均线膨胀系数超出标准外，其余均符合要求，并根据合金化元素的质量磁化系数，依据磁致伸缩理论对基体膨胀性能的影响因素进行了定性的分析。(2)对基体晶粒尺寸的影响，合金化后基体金属的晶粒尺寸相对于未合金化试样16.7μm的晶粒尺寸均有较大的减小。其中单元素W、Mo、Nb合金化，高含量的W和Nb对晶粒大小的影响相当，分别为5.0μm、5.3μm，其次是高含量的Mo和低含量的Nb，分别为6.3μm、6.7μm，最次的是低含量的W，为10.0μm；二元W+Mo、W+Nb、Mo+Nb合金化，其中W+Nb和Mo+Nb对晶粒大小的影响相当，分别为4.8μm、4.5μm，其次是W+Mo，为7.69μm。(3)对基体显微硬度的影响，Nb和Mo合金化对显微硬度HV0.2的影响较大，其中高含量Nb的HV0.2显微硬度值为172.6，相对与未合金化试样128.4的显微硬度值提高了36.0%，低含量的Nb和Mo的显微硬度相当，HV0.2在163左右，最次是W元素，其显微硬度值HV0.2在150左右，但也有提高了12.7%；对二元合金化，W+Nb二元合金化对HV0.2显微硬度的影响最大，其显微硬度HV0.2值为170.3，与未合金化试样相比提高了32.6%，其次为Mo+Nb，其显微硬度HV0.2值为162.0，提高了21.2%，最次是W+Mo，其显微硬度HV0.2值为151，提高了17.6%。(4)从改善合金性能的角度，单元素W、Mo、Nb合金化影响的次序为：高含量Nb最大、其次低含量的Nb、最后为W元素合金化；二元合金W+Mo、W+Nb、Mo+Nb合金化的次序为：W+Nb、W+Mo、Mo+Nb。微观组织以退火孪晶为特点。试验研究表明，选用具有晶粒细化作用的顺铁磁性W、Mo、Nb作为合金化元素，通过细晶强化、形变强化以及二次强化相、退火孪晶亚结构强化等共同作用，提高Fe-Ni因瓦合金的力学性能，并且使合金膨胀性能符合要求。在试验条件下，Nb的作用最为显著，使膨胀合金的强度明显提高并且能保持较低的平均膨胀系数。更多还原

【Abstract】 Lower strength is the characteristic of Fe-Ni low expansion alloy. In recent year,the high strength low thermal expansion (HSLTE) alloy with low coefficient of thermalexpansion (CTE) and high strength has been concerned because of the alloy extendedapplication fields. More and more researchers pay attention to study how to balance thelow coefficient of thermal expansion and high strength and to apply the functionalmaterial as special structural materials.The author chooses the alloying elements with paramagnetic property and grainrefinement ability, based on the metal thermal expansion theory and the comprehensivestrengthening theory of primarily to fine-grain strengthening and the result of Fe-Ni-Xphase diagram by the Factsage software. The key point of influencing the CTE, strengthand stability of Fe-Ni invar alloy was investigated. Then, through the experiment ofmelting under gas shielded, forging process, heat treatment, the key factors ofinfluencing on the invar alloy performance are found out. This provides fundamentalsupport to formulate reasonable process route.(1) The rusults of alloying CTE are obtained. The influence order of single-elementalloying on CTE is W, Nb and Mo, which value has increased about50%,50%and110%, compared with the unalloyed sample. The matrix CTE on binary elemen W+Moand W+Nb is similar and improved62.5%, however that of Mo+Nb improved125%,compared with the unalloyed sample. The CET of alloyed with W, Nb, and W+Nb iscorrespondence with standard requirements, except of alloyed with Mo and Mo+Nb.This influence factors on CTE are analysis according to the theory of magnetostric andthe quality magnetization coefficient.(2) The effects of alloying grain size are analyzed. For single-element W, Mo andNb alloying, the grain size of the matrix has greatly decreased that compared with theunalloyed sample. The results show that the high content W and Nb have similarinfluence on the grain size which is5.0μm and5.3μm respectively. The grain size is 6.3μm and6.7μm after adding high content Mo and low content Nb. The grain size is10.0μm when adding low content W. For binary-element W+Mo, W+Nb and Mo+Nb,the grain size is4.8μm,4.5μm and7.69μm respectively.(3) The effects of alloying microhardness HV0.2are analyzed. The single-elementNb and Mo have great influence on microhardness. The HV0.2of high content Nb is172.6, that has improved36.0%compared with the unalloyed sample. The HV0.2oflow content Nb and Mo is nearly163. The HV0.2of the content W is150, it hasimproved12.7%compared with the unalloyed sample. The influence order ofbinary-element alloying on HV0.2is W+Nb, Mo+Nb and W+Mo, which value is170.3,162.0and151.(4) The impact of single element alloying on improving matrix performance is highcontent Nb, low content Nb, W. That of binary-element is W+Nb, W+Mo and Mo+Nb.The microstructure characteristic is annealing twins.The experimental results show that alloying with ferromagnetic W, Mo and Nb cangreatly fine the grain size of the Fe-Ni invar alloy. The increased strengthening andlower CTE mainly owe to fine grain strengthening, annealing twins sub-structurestrengthening. The effect of Nb alloying on the grain size is the most significant, whichmakes the strength of matrix increase and maintain a low CTE.更多还原