粉末冶金法制备Nb-Si难熔合金及其组织演变与性能研究
发布时间：2019-01-03 21:27
【摘要】：Nb-Si难熔合金的显微组织通常包含铌基固溶体(Nbss)和铌硅化物(Nb_5Si_3/Nb_3Si),由于其高熔点、低密度和良好的高温强度等优点,成为极具潜力的满足新一代航空发动机需求的高温结构材料。但目前广泛应用真空电弧熔炼等铸造方法制备的Nb-Si难熔合金因组织粗大和成分偏析等缺陷影响其性能,并且金属间化合物的本征脆性也阻碍了Nb-Si难熔合金作为高温结构材料的实际应用。本文采用机械合金化+真空热压烧结相结合的粉末冶金方法制备了Nb-Si二元难熔合金以及不同Ti、Fe含量的Nb-Si多元难熔合金(Si含量16at.%),并通过粉末锻造短流程技术成形了发动机推力室模拟件,研究了机械合金化过程中不同混合粉末系统的组织形貌变化以及在不同状态球磨粉末和热压烧结参数下Nb-Si难熔合金的显微组织演变和力学性能,分析了Nb-Si二元合金以及含合金化元素Ti、Fe合金的强韧化机制,考察了材料的高温压缩变形行为以及变形后的显微组织。 对Nb-16Si二元和Nb-16Si-18Ti三元粉末系统机械合金化的研究结果表明无水乙醇用量、初始Nb粉末粒度以及Ti粉末的加入均影响球磨进程。球磨过程中,Nb颗粒经塑性变形成片状而后在加工硬化作用下逐渐细化成絮状,Si逐渐固溶到Nb的晶格中形成过饱和固溶体。过量的无水乙醇推迟了球磨进程,而过长时间的球磨导致介质污染的引入而形成富Fe的另一种铌基固溶体。Ti的低密度使得同质量的粉末体积较大,在相同的球磨参数下三元粉末系统的球磨进程明显慢于二元粉末。 采用真空热压烧结法制备了Nb-16Si二元难熔合金,分析了烧结温度、烧结时间和球磨粉末状态对烧结材料的显微组织演变及力学性能的影响。在1500°C下保温60min得到了致密度超过99.2%的烧结材料,合金由Nbss、Nb3Si和Nb5Si3三相组成,大量孔隙导致低温烧结材料的力学性能较差。随球磨时间的延长热压烧结材料的显微组织逐渐细化为平均颗粒尺寸仅2μm左右的近等轴状,Nbss体积分数减少,大尺寸和高含量的韧性相能够有效改善材料的室温脆性,由此室温断裂韧性降低而弯曲强度增加。在1600°C下采用粉末锻造技术一次成形了Nb-Si难熔合金推力室模拟件,零件具有良好的力学性能和与烧结材料相似的等轴状组织,材料利用率高且成本低。 研究了合金化元素Ti、Fe对热压烧结Nb-Si难熔合金的显微组织演变及力学性能的影响,探讨了组织对性能的影响规律和材料的强韧化机制,考察了高温压缩行为及其变形后的组织。Fe的加入因合成Nb_4FeSi新相而使材料强度提高,但没有改变组织形貌。含Ti的片状复合粉末经烧结后材料的显微组织和性能呈各向异性,在垂直于和平行于热压方向的截面上Nbss分别为平行的条状流线和杂乱的片状。裂纹扩展路径垂直于条状Nbss时塑性变形以及裂纹桥联和偏转等有效提高了材料的断裂韧性,其最高值超过16MPa·m~(1/2),弯曲断口为撕裂棱和韧窝韧性断裂特征,而Ti固溶到Nb中引起的强化使材料获得较好的综合力学性能。垂直于流线方向的高温压缩变形中,Nbss发生塑性压缩且变形后条状Nbss变细,韧性相尺寸影响压缩塑性,而沿流线方向压缩时,变形通过颗粒转动和界面滑移带动片状Nbss向垂直于加载方向偏转。
[Abstract]:The microstructure of the Nb-Si refractory alloy usually contains the base solid solution (Nbss) and the metal silicide (Nb _ 5Si _ 3/ Nb _ 3Si), and has the advantages of high melting point, low density and good high-temperature strength and the like, thus being a high-temperature structural material with great potential to meet the requirements of a new generation of aviation engine. However, the properties of the Nb-Si refractory alloy, such as the coarse and the component segregation of the Nb-Si refractory alloy, are influenced by the defects such as the coarse structure and the component segregation, and the intrinsic brittleness of the intermetallic compound also prevents the practical application of the Nb-Si refractory alloy as the high-temperature structural material. The Nb-Si binary refractory alloy and the Nb-Si multi-element refractory alloy (Si content 16at) with different Ti and Fe content were prepared by mechanical alloying and vacuum hot-press sintering.%) and the engine thrust chamber simulator is formed by a powder forging short flow technique, The microstructure evolution and mechanical properties of different mixed powder systems in mechanical alloying were studied. The microstructure and mechanical properties of Nb-Si refractory alloys under different conditions of ball milling and hot-pressing sintering were studied. The binary alloy of Nb-Si and the alloying elements Ti were analyzed. The toughening mechanism of Fe alloy is studied, and the high temperature compressive deformation behavior of the material and the microstructure after deformation are investigated. The results of the mechanical alloying of the Nb-16Si binary and Nb-16Si-18Ti ternary powder system show that the amount of absolute ethyl alcohol, the particle size of the initial Nb powder and the addition of the Ti powder influence the ball milling. in the process of ball milling, the Nb particles are plastically deformed into a sheet and then gradually refined into a flocculent under the action of the work hardening, and the Si is gradually dissolved into the crystal lattice of the Nb to form a supersaturated solid solution The excess amount of absolute ethyl alcohol has delayed the ball milling process, while over-time ball milling results in the introduction of media contamination to form a rich Fe-rich, one-based solid solution The bulk. Ti low density makes the powder volume of the same mass larger, and the ball milling process of the three-way powder system is obviously slower than that of the binary powder under the same ball milling parameters. In the end, Nb-16Si binary refractory alloy was prepared by vacuum hot-pressing and sintering, and the microstructure and mechanical properties of the sintered materials were analyzed. The sintering material with density of more than 99.2% is obtained at 1500 掳 C for 60min. The alloy is composed of three phases of Nbss, Nb3Si and Nb5Si3, and a large number of pores lead to the mechanical property of low-temperature sintered materials. the microstructure of the hot-pressed sintered material with the ball grinding time is gradually refined into a near equiaxed form with the average particle size of only about 2. m u.m, the volume fraction of the Nbss is reduced, the large-size and the high-content toughness phase can effectively improve the chamber of the material, the temperature is brittle, thus the fracture toughness of the room temperature is reduced and the bending strength is strong. Nb-Si refractory alloy thrust chamber simulation part is formed at a time of 1600 DEG C by a powder forging technology, the part has good mechanical property and the equiaxed structure similar to that of the sintered material, and the material utilization rate is high; The effects of alloying elements Ti and Fe on microstructure evolution and mechanical properties of hot-pressed sintered Nb-Si refractory alloys have been studied. The influence of the microstructure on the properties and the mechanism of strengthening and toughening of the materials are discussed. The high-temperature compression behavior and its change are also investigated. The addition of Fe increases the strength of the material due to the new phase of the synthesis of Nb _ 4FeSi, but has not changed. the microstructure and the property of the flaky composite powder containing Ti are anisotropic, and the Nbss in the cross-section perpendicular to and parallel to the hot-pressing direction is a parallel strip-shaped streamline and The crack propagation path is perpendicular to the strip-shaped Nbss, the plastic deformation and the crack bridge and the deflection can effectively improve the fracture toughness of the material, the maximum value of which is more than 16MPa 路 m ~ (1/ 2), and the bending fracture is the tearing edge and the tough-and-socket. The characteristics of the fracture characteristics, and the strengthening of Ti to the Nb causes the material to obtain a better harness. in the high-temperature compressive deformation perpendicular to the flow direction, the Nbss is plastically compressed and the deformed bar-shaped Nbss is thin, the size of the toughness phase influences the compression plasticity, and when compressed in the direction of the flow line, the deformation passes through the particle rotation and the interface slip to drive the flaky Nbss to be perpendicular to the addition
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：TG132.32;TF124.3
本文编号：2399892
[Abstract]:The microstructure of the Nb-Si refractory alloy usually contains the base solid solution (Nbss) and the metal silicide (Nb _ 5Si _ 3/ Nb _ 3Si), and has the advantages of high melting point, low density and good high-temperature strength and the like, thus being a high-temperature structural material with great potential to meet the requirements of a new generation of aviation engine. However, the properties of the Nb-Si refractory alloy, such as the coarse and the component segregation of the Nb-Si refractory alloy, are influenced by the defects such as the coarse structure and the component segregation, and the intrinsic brittleness of the intermetallic compound also prevents the practical application of the Nb-Si refractory alloy as the high-temperature structural material. The Nb-Si binary refractory alloy and the Nb-Si multi-element refractory alloy (Si content 16at) with different Ti and Fe content were prepared by mechanical alloying and vacuum hot-press sintering.%) and the engine thrust chamber simulator is formed by a powder forging short flow technique, The microstructure evolution and mechanical properties of different mixed powder systems in mechanical alloying were studied. The microstructure and mechanical properties of Nb-Si refractory alloys under different conditions of ball milling and hot-pressing sintering were studied. The binary alloy of Nb-Si and the alloying elements Ti were analyzed. The toughening mechanism of Fe alloy is studied, and the high temperature compressive deformation behavior of the material and the microstructure after deformation are investigated. The results of the mechanical alloying of the Nb-16Si binary and Nb-16Si-18Ti ternary powder system show that the amount of absolute ethyl alcohol, the particle size of the initial Nb powder and the addition of the Ti powder influence the ball milling. in the process of ball milling, the Nb particles are plastically deformed into a sheet and then gradually refined into a flocculent under the action of the work hardening, and the Si is gradually dissolved into the crystal lattice of the Nb to form a supersaturated solid solution The excess amount of absolute ethyl alcohol has delayed the ball milling process, while over-time ball milling results in the introduction of media contamination to form a rich Fe-rich, one-based solid solution The bulk. Ti low density makes the powder volume of the same mass larger, and the ball milling process of the three-way powder system is obviously slower than that of the binary powder under the same ball milling parameters. In the end, Nb-16Si binary refractory alloy was prepared by vacuum hot-pressing and sintering, and the microstructure and mechanical properties of the sintered materials were analyzed. The sintering material with density of more than 99.2% is obtained at 1500 掳 C for 60min. The alloy is composed of three phases of Nbss, Nb3Si and Nb5Si3, and a large number of pores lead to the mechanical property of low-temperature sintered materials. the microstructure of the hot-pressed sintered material with the ball grinding time is gradually refined into a near equiaxed form with the average particle size of only about 2. m u.m, the volume fraction of the Nbss is reduced, the large-size and the high-content toughness phase can effectively improve the chamber of the material, the temperature is brittle, thus the fracture toughness of the room temperature is reduced and the bending strength is strong. Nb-Si refractory alloy thrust chamber simulation part is formed at a time of 1600 DEG C by a powder forging technology, the part has good mechanical property and the equiaxed structure similar to that of the sintered material, and the material utilization rate is high; The effects of alloying elements Ti and Fe on microstructure evolution and mechanical properties of hot-pressed sintered Nb-Si refractory alloys have been studied. The influence of the microstructure on the properties and the mechanism of strengthening and toughening of the materials are discussed. The high-temperature compression behavior and its change are also investigated. The addition of Fe increases the strength of the material due to the new phase of the synthesis of Nb _ 4FeSi, but has not changed. the microstructure and the property of the flaky composite powder containing Ti are anisotropic, and the Nbss in the cross-section perpendicular to and parallel to the hot-pressing direction is a parallel strip-shaped streamline and The crack propagation path is perpendicular to the strip-shaped Nbss, the plastic deformation and the crack bridge and the deflection can effectively improve the fracture toughness of the material, the maximum value of which is more than 16MPa 路 m ~ (1/ 2), and the bending fracture is the tearing edge and the tough-and-socket. The characteristics of the fracture characteristics, and the strengthening of Ti to the Nb causes the material to obtain a better harness. in the high-temperature compressive deformation perpendicular to the flow direction, the Nbss is plastically compressed and the deformed bar-shaped Nbss is thin, the size of the toughness phase influences the compression plasticity, and when compressed in the direction of the flow line, the deformation passes through the particle rotation and the interface slip to drive the flaky Nbss to be perpendicular to the addition
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：TG132.32;TF124.3
【参考文献】
中国期刊全文数据库 前10条
1 丁旭,郭喜平;新型铌-硅基共晶自生复合材料的研究进展[J];材料导报;2003年11期
2 马勤,康沫狂;高温结构硅化物研究的新进展[J];材料工程;1997年07期
3 李伟,杨海波,单爱党,吴建生;Mo对于Nb/Nb_5Si_3原位复合材料室温韧性的影响[J];材料工程;2004年04期
4 宋立国;曲士昱;宋尽霞;李树索;宫声凯;韩雅芳;;1250℃热处理对Nb-16Si-24Ti-6Cr-6Al-2Hf合金的组织影响[J];材料工程;2005年12期
5 李宗霞;机械合金化─研制生产金属材料的一种新工艺[J];材料工程;1995年11期
6 张德尧,肖联贞;C—103铌合金环件工艺研究[J];稀有金属材料与工程;1985年05期
7 张德尧,肖联贞;C-103铌合金推力室模锻工艺研究[J];稀有金属材料与工程;1986年01期
8 朱心昆,林秋实,陈铁力,程抱昌,曹建春;机械合金化的研究及进展[J];粉末冶金技术;1999年04期
9 王尔德,胡连喜;机械合金化纳米晶材料研究进展[J];粉末冶金技术;2002年03期
10 杨君友，张同俊，李星国，，崔];机械合金化研究的新进展[J];功能材料;1995年05期
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