FGH95镍基合金的电解萃取及相组成与分布特征

通过对热处理态FGH95合金进行电解萃取,组织形貌观察及XRD分析,研究了FGH95合金的相组成及γ′相的粒度分布.结果表明,经1140℃固溶和时效处理后,合金的组织结构由γ′,γ相,(Nb,Ti)C、( Nb,W)B2,Nb13B2和Cr23C6等碳、硼化物组成,其中合金中γ′,γ基体相的质量分数分别为47.8％和51.2％,其碳、硼化物的质量分数约为1％.合金中晶内为细小γ′相弥散分布,而粗大γ′相沿较宽的颗粒边界区域不连续析出;其中,在36～60nm之间的γ′相粒子质量分数为30.6％,在60～96nm之间的γ′相粒子质量分数为29.1％,γ′相的结构组成式为:(Ni0.896C00.055Cr0.017Fe0.031)3 (Ti0.224Nb0.134Al0.473Mo0.038W0.066 Cr0.064).     

超超临界电站用镍铁基高温合金TCP相和碳化物相析出的热力学计算

利用材料相图与性能模拟计算软件JMatPro,研究了难熔元素W,Mo,Nb和Fe含量的变化对一种新型镍铁基高温合金拓扑密排相(TCP)和碳化物相析出及高温性能的影响。结果表明:新型镍铁基高温合金晶内强化相为γ′相,晶界为M23C6碳化物;在合金中添加Mo,W,Nb均可提高合金的持久强度和屈服强度;增加合金中Mo,Nb,Fe的含量会提高Laves相和σ相的析出温度;为避免在长期服役过程中合金析出较多的TCP相,在合金中添加不超过0.6%(质量分数,下同)的Nb或不超过1%的Mo和W,以使TCP相的析出温度尽可能低于使役温度。     

长期时效对DZ951合金γ′相的影响

研究了定向凝固DZ951镍基高温合金在长期时效过程中的组织演化。结果表明：随着时效温度和时间的增加，γ′粗化形筏。形筏时间随时效温度的升高而减少。形筏驱动力为弹性应变能和界面能的降低。γ′长大受元素扩散控制，长大遵循LSW理论，长大激活能为294kJ／mol左右。由于DZ951合金γ′相中含有较多的高熔点元素W，Mo和Nb等，从而提高γ′相的稳定性，增加γ′长大激活能。合金在长期时效过程中未出现拓扑密排相（Topological Close-Packed Phase，TCP Phase）等有害相，表明DZ951合金具有较好的组织稳定性。     

新型钴基高温合金成分设计的研究进展

传统钴基高温合金的强化机制为固溶强化和碳化物强化,弱于有序γ′相沉淀强化的镍基高温合金的强化效果,日本学者发现了有序γ′相强化的Co-Al-W系新型钴基高温合金,其强化效果明显优于传统钴基高温合金。由于新型钴基高温合金具有较传统镍基高温合金更高的承温能力以及更加优异的高温抗蠕变性能和抗氧化性能,因此被认为是最具潜力的航空发动机热端材料之一,近年来得到迅速发展。基于国内外学者对新型钴基高温合金的研究成果,系统总结多种合金元素(如Ta, Ti, W和Nb等)对新型钴基高温合金组织和性能的影响。在组织方面,总结合金元素对合金相变温度、γ′相的体积分数及形态、γ′相的尺寸、γ/γ′两相晶格错配度和有害相的影响;在性能方面,总结合金元素对合金抗氧化性能、力学性能及抗蠕变性能的影响,以期为新型钴基高温合金的成分设计提供参考。最后对新型钴基高温合金成分的高效率设计进行展望。     

Nb对PREP法制备内燃机用IN718粉末合金组织和温拉伸性能的影响

采用等离子旋转电极法制备了包含γ′相的镍基粉末高温合金,并对合金中含有不同Nb比例时显微组织结构的改变进行分析,同时对其处于650℃下力学性能进行了测试。研究结果表明:经过热处理后,在γ相内形成了γ′相,当Nb比例从0%提高至3.0%时,γ′相的微观形貌始终保持方形的结构,添加Nb之后形成了更加粗大的γ′相。相对于未加Nb,当在合金内添加Nb之后,试样拉伸强度增大了120MPa以上。试样拉伸强度随Nb含量增加而逐渐增加。Nb能够显著提升合金高温强度,存在一个最优Nb含量使试样获得最佳高温塑性。含3.0%Nb的合金组织发生了塑性断裂,合金中形成了明显延伸的断口,存在众多小尺寸等轴韧窝。当Nb含量增大后,合金发生了塑性降低。含3.0%Nb的合金在拉伸过程中形成了孪晶并降低了滑移带的数量,增加Nb含量后有助于生成层错组织。     

GH169合金中的γ''''、γ"及δ相

一、前言 GH169合金(Inconel 718)是一种时效硬化Ni-Cr-Fe基变形高温合金,在650℃下该合金具有很高的强度、韧性、疲劳性能及良好的综合性能。合金中主要有γ’、γ”、δ相以及各种夹杂相。 γ”相为亚稳相,是GH169合金的主要强化相;γ’相也是亚稳相,强化效果次于γ”相;δ相的组成虽与γ”相相同,但无明显的强化作用。γ’和γ”相的稳定性直接影响到合金的热稳定性。Wachtel和Rack总结有关Inconel718合金的研究,认为该合金中存在如下相反应: γ相→γ’相→γ”相→δ相 为提高合金的热稳定性,Pineau采用调整强化元素Nb、Ti、Al的比例和增加Mo元素来得到盘片状γ”相包覆立方形六面体γ’相的γ’相+γ”相包覆组织,但由于强化元素Nb含量的减少而导致合金强度下降。本文对不改变成分的GH169合金中γ’相和γ”相共格生长复合组织及δ相的一般特征进行研究。     

FeNiCr WMoTi合金中γ′数量和尺寸及其强硬化效应

研究了Fe 2 8Ni 13Cr 1W 1.5Mo 2Ti 0 .5Nb 0 .2Al高温合金不同时效状态下γ′相的数量和尺寸对强硬化效应的影响。在 16h时效条件下 ,随时效温度升高 (在 6 5 0～ 730℃ ) ,由于γ′粒子尺寸增大速率较小 (从 7～ 14nm ) ,其数量显著增多 ,因而合金的硬化效应增大 ;温度在 730～76 0℃时 ,在位错的Orowan绕过机制启动之前 ,虽然γ′相数量随时效温度升高继续增多 ,但由于尺寸显著增大 ,合金的硬化效应明显降低。在位错以切割方式通过γ′粒子的尺寸范围内 ,沉淀出精细γ′粒子的合金状态比析出相同数量粗大γ′粒子的合金状态具有更高的室温硬化效应     

Co-Al-W基高温合金发展概述

传统Co基高温合金的强化机制为固溶强化与碳化物强化,强化效果弱于Ni基高温合金中的有序相γ'强化,从而使得Co基高温合金的应用受到限制。直到2006年,在Co-Al-W三元相图中发现稳定的L12相——Co3(Al,W),这种新型γ'相强化的Co-Al-W基高温合金有以下特点:(1)含Ta合金熔点高于Waspaloy合金;(2)硬度与屈服强度不低于Ni基高温合金;(3)γ/γ'两相之间的晶格错配度与Ni基高温合金在数值上接近,符号上相反,而正的晶格错配度更有利于蠕变性能。综上所述,Co3(Al,W)相的发现为Co基高温合金的发展开辟了新道路。自2006年以来,针对Co-Al-W基高温合金的组织与性能进行了大量研究。Co-Al-W基高温合金的微观组织为γ/γ'两相,此外还会存在一些二次相,其中包括富集Al和Ti元素的B2-CoAl相、富集难熔元素的拓扑密堆相m-Co7W6以及易在时效过程析出的c-Co3W相。这些二次相通常在晶界析出,容易成为裂纹的发源地,同时会弱化固溶强化效果,对合金的高温性能不利。虽然Co-Al-W基高温合金得到了立方形态的γ'相共格析出,但由于γ'-Co3(Al,W)相高温稳定性差,需要对其进行合金化,因此,这种γ'相强化的Co基高温合金正在由简单的Co-Al-W三元合金发展成为复杂的多元合金。综合来看,主要添加的合金化元素有Ta、Ti、Nb、V、Mo、Ni和Cr。其中,γ'相形成元素包括Ta、Ti、Nb、V、Mo,这些元素的分配系数均大于1,且能有效提高γ'相固溶温度与体积分数; Cr、Fe、Re的分配系数小于1,是γ相形成元素,添加后均降低γ'相固溶温度,其中Cr会提高γ'相的体积分数。众多合金元素中,Cr、Mo和Ni元素的过量添加会降低γ/γ'两相间的晶格错配度,从而改变γ'相形态甚至破坏γ/γ'两相组织。合金的组织与性能密切相关,γ/γ'两相、γ'相为立方形态且γ'相高温稳定性高的合金具有优异的性能。Co-Al-W基高温合金的流变应力随温度变化分为三个阶段:首先随温度升高而降低;然后随温度升高而异常升高;最后再次随温度升高而降低。故而存在峰值温度与峰值强度,Co基高温合金多应用在峰值温度下,以便获得最高的屈服强度。此外,由于Co-Al-W基高温合金中γ/γ'两相晶格错配度为正,在蠕变过程中会出现平行于拉应力的筏化,对合金的高温性能有利。除了Ta、Ti等元素能强化合金外,少量B元素的添加有晶界强化作用,可以提高合金的力学性能。添加Cr元素的Co-Al-W基高温合金在高温氧化过程中会形成三层氧化层,分别是最外层的Al_2CoO_4、富Cr并含有Cr2O和Cr2O3的中间层以及最内层的Al_2O_3。其中Cr_2O_3和Al_2O_3氧化层均致密且具有保护作用,可显著提高合金的抗氧化能力。本文简单介绍了Co-Al-W基高温合金的发现与发展,综述了近年来Co-Al-W基高温合金的研究现状,并指明了未来Co基高温合金的发展方向。     

GH742中γ′相和γ基体成分随时效时间和温度的变化规律研究

利用透射电镜能谱法(TEM-EDX)研究了GH742合金中γ′和γ基体两相成分随温度和时效时间的变化规律.结果表明:合金在1050℃时效时,γ′相和γ基体的成分在时效初期变化较大,当时效时间超过1440min后,γ′相和γ基体的成份基本稳定.合金在750～1100℃时效时,γ′相和γ基体的成分均随着温度的升高而发生变化,其中γ基体的成分随温度变化较明显.合金中各元素在γ′和γ两相中的偏析率Cγ′/ Cγ变化规律研究表明:Ti,Al,Nb,Ni等γ′形成元素的偏析率均随着时效温度的升高而降低,而Cr,Co,Mo等γ形成元素的偏析率均随着时效温度的升高而增大.     

Nb、Cr和Mo对新型β/γ-TiAl合金组织与相变的影响

为了研究TiAl合金中β相稳定元素对显微组织及相变温度的影响,本文在Ti-43Al合金的基础上,通过单独与复合添加Nb、Cr、Mo 3种合金元素,获得了新型β/γ-TiAl合金,并系统研究了3种元素的作用规律.结果发现:Nb促使合金形成片层结构,Cr、Mo使合金分别形成近γ组织和针状魏氏组织;3种元素对β相的稳定能力为Mo>Nb>Cr;复合添加Nb、Cr、Mo元素对β相的稳定作用比单一添加更为显著;3种不同元素对α+β+γ三相区范围有显著影响,对α2+γ→α转变的共析温度(te)影响较大,而对γ→α的转变温度(tα)影响较小,Ti-43Al-4Nb-2Mo-0.2B合金的α+β+γ三相区最窄约为15℃,而Ti-43Al-6Nb-0.2B合金的α+β+γ三相区最宽约为95℃,Ti-43Al-4Nb-1Cr-1Mo-0.2B合金的α+β+γ三相区为55℃.     

合金元素对 Nb2Mo2Si合金相平衡及Nb2 Nb 5Si 3共晶组织形态的影响

采用电弧熔炼法制备了 Nb220Si210Mo、Nb220Si210Mo23M (M = Cr , Al , Ti) (原子分数) 四种 Nb2Mo2Si基超高温合金。利用 SEM、EDS、XRD等实验技术对铸造合金的相组成与组织形态进行了观察和分析。Nb220Si210Mo 合金由铌固溶体 (Nb SS) 与βNb 5Si 3化合物两相构成 , 其铸造组织包含大量片层状共晶 (Nb SS 2βNb 5Si 3) 组织。少量合金元素 Cr (3 at %) 能够改变 Nb220Si210Mo 合金的相平衡关系 , Nb220Si210Mo23Cr 的铸造组织中不仅存在 Nb SS和βNb 5Si 3 , 而且还出现少量 Cr 2Nb相 ; 而添加合金元素 Al、Ti (3 at %) 并不改变 Nb220Si210Mo 合金的相平衡关系。添加 Cr 使 Nb SS 2 βNb 5Si 3共晶组织失去了平直片层特征 ; Al 有利于共晶组织中片层状共晶形成 ; 添加 Ti使共晶组织呈现羽毛状特征。合金化使 Nb与βNb 5Si 3的晶格常数发生变化 : Nb的晶格常数均变小; Nb220Si210Mo23Cr合金中βNb 5Si 3的 c/ a值减小 , 其它 3种合金中βNb 5Si 3的 c/ a值增大。     

Effect of Nb on the Microstructure and Mechanical Properties of Cast NiAl-Cr（Mo） Eutectic Alloy

The microstructure and mechanical behaviors of NiAl-28Cr-5Mo-1Nb eutectic alloy were investigated by using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and compression tests, respectively. The alloy is mainly composed of three phases, which are the gray lamellar Cr（Mo） plate, black NiAI matrix and semicontinuously distributed Cr2Nb-type Laves phase. Through Nb addition, NiAl-Cr（Mo）/Nb alloy exhibits a reasonable balance of high temperature strength and room temperature compression ductility and its mechanical behaviors are superior to the NiAl-28Cr-6Mo eutectic alloy at all temperature. The elevated temperature compression deformation behavior of NiAl-Cr（Mo）/Nb alloy can be properly described by power-law equation.the National High Technology Committee of China （No. 863-715-005-0030） for financial supports.     

Phase evolution and crystallography of precipitates during decomposition of new “tungsten-free” Co(Ni)–Mo–Al–Nb γ–γ′ superalloys at elevated temperatures

This article reports the microstructural stability and consequent phase decomposition including the appearance of topologically close-packed (TCP) phases at high temperature of recently discovered tungsten-free γ–γ′ alloys of base composition Co–10Al–5Mo–2Nb with or without the addition of Ni and Ti. On prolonged aging at 800 °C of the Co–10Al–5Mo–2Nb alloy, needle-shaped DO₁₉-ordered precipitates with stoichiometry of Co₃(Mo, Nb) start appearing in the microstructure. In addition, growth of cellular domains from the grain boundaries featuring a three-phase composite lamellar structure could be observed. These phases are fcc γ-Co with composition different from the original matrix, CoAl with B2 ordering and Co₃(Mo, Nb) with DO₁₉ ordering. All the phases exhibit well-defined crystallographic orientation relationships. The decomposition of the alloys depends on the solvus temperature of the γ′ phase. The Ni-containing alloy exhibits no phase decomposition until 100 h of aging at 800 °C without any significant effect on γ′ volume fraction (76 %). However, at 950 °C, the alloy decomposes leading to the appearance of four different phases including TCP phases: a Cr₃Si-type cubic phase, a hexagonal Laves phase, rhombohedral μ phase, and solid solution of Co phase. The γ–γ′ microstructure in the Co–10Al–5Mo–2Nb and Co–30Ni–10Al–5Mo–2Ta alloys is not stable at 800 and 950 °C, respectively, on long-term aging. This shows that the measured solvus temperatures (i.e., 866 and 990 °C) are metastable solvus temperatures. We also report that the Ti-containing alloy exhibits superior stability with no evidence of either TCP phase formation or any other decomposition of γ′ precipitates, even after aging at 950 °C for 100 h.     

Structure,mechanical properties and grindability of dental Ti–10Zr–X alloys

This study aimed to investigate the structure, mechanical properties and grindability of a binary Ti–Zr alloy added to a series of alloying elements (Nb, Mo, Cr and Fe). The phase and structure of Ti–10Zr–X alloys were evaluated using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. Three-point bending tests were performed using a desk-top mechanical tester. Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m/min). Results were compared with c.p. Ti, which was chosen as a control. Results indicated that the phase/crystal structure, microstructure, mechanical properties and grindability of the Ti–10Zr alloy can be significantly changed by adding small amounts of alloying elements. The alloying elements Nb, Mo, Cr and Fe contributed significantly to increasing the grinding ratio under all grinding conditions, although the grinding rate of all the metals was found to be largely dependent on grinding speed. The Ti–10Zr–1Mo alloy showed increases in microhardness (63%), bending strength (40%), bending modulus (30%) and elastic recovery angle (180%) over those of c.p. Ti, and was also found to have better grindability. The Ti–10Zr–1Mo alloy could therefore be used for prosthetic dental applications if other conditions necessary for dental casting are met.     

磁控溅射Cu-Nb和Cu-Mo薄膜结构与性能

采用磁控溅射制备含1.16%～15.8%(原子分数)Nb的Cu-Nb及含2.2%～27.8%Mo的Cu-Mo合金薄膜,井采用EDX、XRD、SEM、显微硬度仪和电阻计对薄膜的成分、结构和性能进行研究。结果表明,Nb和Mo的添加分别使Cu-Nb及Cu-Mo薄膜晶粒显著细化,Cu-Nb和Cu-Mo薄膜呈纳米晶结构,存在Nb在Cu中的fcc Cu(Nb)和Mo在Cu中的fcc Cu(Mo)非平衡亚稳过饱和固溶体,固溶度随Nb或Mo含量增加而上升。添加Nb和Mo显著提高Cu-Nb及Cu-Mo薄膜的显微硬度和电阻率,且随Nb或Mo含量增加而升高。经650℃热处理1h后,Cu-Nb和Cu-Mo薄膜显微硬度和电阻率均下降,且分析表明均发生基体相晶粒长大,并出现微米-亚微米级富Cu第二相,Cu-Nb及Cu-Mo薄膜结构和性能形成及演变的主要原因是添加的Nb、Mo引起的晶粒细化效应以及退火中基体相晶粒度的增大。     

Ti-10Mo-XNb合金铸态组织和机械性能的研究

为了研究Nb元素对Ti-10Mo合金组织和性能的影响,采用钨电极熔化、离心浇注工艺制备了4种钛合金(Ti-10Mo-XNb,X=0,3,7,10),分析并测试了Nb元素对Ti-10Mo合金铸态组织和力学性能的影响.研究结果表明:随着Nb含量的增加,3种Ti-Mo-Nb合金的铸态组织和相组成发生了改变,Ti-10Mo-3Nb合金由等轴的α+β晶粒组成,Ti-10Mo-7Nb合金由等轴的β晶粒组成,Ti-10Mo-10Nb合金由少量等轴和大量枝状的β晶粒组成.另外,随着Nb含量的增加,3种Ti-Mo-Nb合金的维氏硬度、压缩强度、弹性模量降低,压缩率和抗弯强度升高,压缩断口和弯曲断口由脆性断裂向韧性断裂转变.Ti-Mo-Nb合金有望成为新型的生物医用材料.     

Effects of microalloying and ceramic particulates on mechanical properties of TiAl-based alloys

Micro-alloyed titanium aluminides and TiAl-based composite with a fully dense structure have been synthesized by a powder metallurgical method. X-ray diffraction and EDX studies show that the monolithic TiAl-based alloy and its composite consist of TiAl and Ti₃Al compounds with the former as the major phase. Additions of Nb and/or (Mo + Cr) exert remarkable effects on the resultant phase compositions and mechanical properties of TiAl-based alloys. Both the added Mo and Cr elements are dissolved into the TiAl-based compounds to exhibit solid solution strengthening effect whereas Nb is only partially dissolved and the rest appears in the Nb-rich compound, Nb₂Al. In general, the micro-alloyed TiAl and the composite exhibit superior flexural strength and fracture toughness to TiAl-based monolithic compound.     

Achievement of Ultralow Elastic Modulus through Optimization of Phase Stability and Recrystallization Texture in Ti–Nb–Fe–Sn Alloys

Ti–Nb–Fe–Sn alloys with relatively low Nb content, located near the phase boundary of (β + ω)/β, are designed on the basis of electron-to-atom (e/a) ratio, d-electron alloy design concept, and Mo equivalent (Mo_eq) aiming at low Young's modulus comparable to human bone. The effect of Sn content and Nb content on the microstructure and the mechanical properties is investigated in Ti–5Nb–3Fe–(0–6)Sn (at%) and Ti–(3–9)Nb–3Fe–4Sn (at%) alloys. The composition dependence of Young's modulus and tensile strength of Ti–Nb–Fe–Sn alloys is analyzed in terms of the phase stability, ω phase, and recrystallization texture. Both Nb and Sn are effective in suppressing the athermal ω phase and stabilizing the β phase. The recrystallization texture is strongly influenced by the content of Sn and Nb. A strong {110}_β<001>_β Goss texture is formed in the Ti–5Nb–3Fe–(2–4)Sn and Ti–(3–5)Nb–3Fe–4Sn alloys. The Ti–5Nb–3Fe–4Sn alloy exhibits an exceptionally low Young's modulus of 30 GPa due to the combined effects of low stability of the β phase, a small amount of ω phase, and a strong Goss texture.     

Order-disorder transformation of the body centered cubic phase in the Ti-Al-X (X = Ta, Nb, or Mo) system

The ordering of the bcc phase present in the Ti-Al-X (X = Ta, Nb, or Mo) system is investigated in this paper. There is a ternary phase of ordered bcc (B2) structure near the composition Ti-25Al-25X. All compositions mentioned in this paper are in atomic percent, unless mentioned otherwise. The phase reactions in Ti-33Al-17Ta alloy are examined in detail following solidification and solid-state processing treatments. It can be found from the differential thermal analysis (DTA) that the B2 phase in this alloy is stable up to 1205°C, where it experiences a solid-state order to disorder transformation. The rate of this ordering reaction is so high that it cannot be arrested by rapid solidification processing (RSP). The presence of thermal antiphase boundaries (APBs) in the microstructure confirms the solid-state ordering of the B2 phase from the disordered bcc phase. Ordering reactions involving the bcc phase in the Ti-Al-Nb and Ti-Al-Mo systems are also studied because of their similarity with the Ti-Al-Ta system. It can be found that they are also solid-state ordering reactions. In the Ti-25Al-25Nb alloy the B2 phase is ordered up to 1141°C; whereas in the Ti-25Al-25Mo alloy the B2 phase is ordered up to 1418°C.     

The high- and low-cycle fatigue behavior of Ni-contain steels and Ni-alloys in high pressure hydrogen

The effect hydrogen on short-term strength and plasticity, high- and low-cycle durability of 15Cr12Ni2MoNMoWNb martensitic steel, 10Cr15Ni27Ti3W2BMo austenitic dispersion-hardened steel, 04Kh16Ni56Nb5Mo5TiAl and 05Kh19Ni55Nb2Mo9Al Ni-base superalloys in range of pressures 0–30 MPa and temperatures 293–1073 K was investigated. In the case of 15Cr12Ni2MoNMoWNb steel and 04Kh16Ni56Nb5Mo5TiAl alloy the dependence of low-cycle durability (N) and characteristics of plasticity (δ and ψ) on the hydrogen pressure consists of two regions. In the first region (low pressures), the N, δ and ψ abruptly drops, and in the second, the negative action of hydrogen becomes stable or decrease negligibility. This means that there exists a pressure under which the degradation of this material with hydrogen reaches its limit. The additional effect of preliminary dissolved hydrogen on the properties of 15Cr12Ni2MoNMoWNb steel and 04Kh16Ni56Nb5Mo5TiAl alloy developed at hydrogen environment pressure least of 10 MPa. In the case of 10Cr15Ni27Ti3W2BMo steel and 05Kh19Ni55Nb2Mo9Al alloy the low-cycle durability N, characteristics plasticity δ and ψ decrease in whole hydrogen pressure range. Preliminary dissolved hydrogen leads to a considerable additional decrease in the properties of this alloy.