粗颗粒钨粉对90W-Ni-Fe钨合金烧结变形与组织性能的影响

在原材料粉末中添加20μm的粗颗粒钨粉,用粉末冶金法制备了圆柱状90W-Ni-Fe钨合金。通过测量钨合金烧结坯椭圆状横截面长短轴的尺寸,对烧结变形进行了定量分析;采用准静态拉伸试验对合金的力学性能进行了测试;通过光学金相、扫描电镜对合金组织形貌进行表征。结果表明:添加粗颗粒W粉能明显降低合金烧结变形,粗颗粒钨粉添加量占钨粉总量80%时,圆柱状钨合金投料可降低约20%,明显提高材料利用率;当粗颗粒W粉含量在70%~90%之间时,合金抗拉强度约950 MPa,延伸率约20%,与未添加粗颗粒钨粉的传统90W-Ni-Fe钨合金相比,其强度提高约30MPa,延伸率降低了28.5%,这与添加粗颗粒W粉的钨合金的穿晶断裂方式,以及合金界面结合强度低、黏结相分布不均匀等有关;添加粗颗粒钨粉的钨合金微观组织中的钨晶粒形状不太规则,存在粒径超大的钨晶粒。     

应变率对钨合金抗拉强度及断口形貌的影响

对四种热加工工艺的钨合金进行了１０＾－４－１０＾３Ｓ＾－１的动态拉伸实验。随着应变率逐渐增大，高强度材料速率敏感性低，低强度材料敏感性高。断裂模式由钨颗粒与基体粘接相界面脱开的韧性断裂向钨颗粒解理的脆性断裂转变。     

真空处理对GW-7W合金力学性能的影响

本文研究了真空处理态和烧结态的GW-7W合金微观结构、氢含量和力学性能以及拉伸、断裂韧性试样断口的微观形貌。指出经过1200℃真空处理,合金中的氢降低,钨颗粒和基体界面之间结合力加强,抗拉强度和延伸率大幅度提高。由于断裂韧性是强度和延性的综合表现,随着合金延伸率和抗拉强度的增加,韧性得到改善。另外由于消除氢脆,钨颗粒和基体之间结合力增强,裂纹沿合适位向的(001)面扩展的机率增多,所以真空处理后的GW-7W合金,拉伸和断裂韧性试样断口解理面比烧结态试样增多。     

高温合金中钨元素的看谱分析技术应用研究

对高温合金中钨元素的看谱分析技术进行了研究,摄制并标定了高温合金中钨元素的彩色图谱,制定了半定量分析测定用强度标。研究结果可用于高温合金中钨元素的定性和半定量分析及材料牌号鉴别。     

钨合金低温塑性降低机理及断口分析

对旋锻正火态的９３ＷＮｉＦｅ合金进行不同温度的动态拉伸实验,拉伸速率１０ｍ／ｓ,温度为４７３￣７７Ｋ。随着温度的降低,钨合金的塑性降低,断口形貌由高温钨颗粒与基体脱粘的韧性断裂逐渐向低温钨颗粒解理脆性断裂转变。钨合金低温塑性降低的机理是温度降低时,钨颗粒的变形逐渐被抑制。提出了不同温度下钨合金变形与断裂模型。     

合金元素钴和锰对W－Ni－Fe合金性能的影响

在ｗ－Ｎ－Ｆｅ三元合金中加入少量的钴和锰，则明显地改善了合金的性能。文中比较了合金的强度和延伸率，讨论了提高合金性能的主要原因，认为：钴和锰的加入改善了合金中基体相的性质，增加了钨相和基体相的界面结合力，有利于提高合金的机械性能。     

Na元素掺杂方式对超粗晶碳化钨及其合金性能的影响

对比研究了在仲钨酸铵(APT)中掺杂Na元素和在黄钨中掺杂Na元素对钨粉、碳化钨粉及其合金性能的影响规律及作用机制。结果表明:由于APT中掺入的Na_2WO_4·2H_2O在煅烧过程中充分转变为Na_2W_2O_7,利于在后续的黄钨还原过程中生成低熔点的钨青铜Na_2O·xWO_3,易于获得粒度较粗的钨颗粒;APT中掺钠获得的钨粉和碳化钨粉末颗粒粒度均大于黄钨中掺钠的粉末颗粒粒度,且前者制备的超粗晶WC-10Co合金性能优于黄钨掺Na的合金。     

合金元素钴和锰对W—Ni—Fe合金性能的影响

在Ｗ－Ｎ－Ｆｅ三元合金中加入量的钴和锰，则明显地改善了合金的性能，文中比较了合金的强度和延伸率，讨论了提高合金性能的主要原因，认为：钴和锰的加入改善了合金中基体相的性质，增加了钨相和基体相的界面结合力，有利于提高合金的机械性能。     

添加Co,La元素对90W-Ni-Fe合金性能和组织的影响

采用扫描电镜（SEM）、X射线能谱仪（EDS）等，研究在氢气保护、真空烧结条件下添加不同含量的Co、La合金元素对90W-Ni—Fe合金显微组织及性能的影响。结果表明：加入适量的Co、La元素，可以改善粘结相与钨颗粒间的润湿性，La以固溶强化的方式强化钨颗粒及粘结相，从而提高了合金性能。当Co、La元素含量为1．1％（质量分数）时，合金中出现了La的富集与氧的偏析，导致合金性能降低；当添加0．7％的Co、La时，试样强度及伸长率出现极大值，分别为930MPa和24．0％；添加0．5％的Co、La时，试样相对密度出现99．30％的极大值。     

SPS循环次数对车曲轴用86W-12.5Ni-1.2Al-5.5Fe-1.5Al2O3钨合金组织及性能的影响北大核心

利用放电等离子烧结(SPS)技术对86W-12.5Ni-1.2Al-5.5Fe-1.5Al2O3车曲轴用钨合金进行处理,研究了循环次数对其组织及性能的影响。结果表明:当SPS循环次数增加后,试样内形成了更均匀的钨晶粒(W)与粘结相(M),W-W连接度降低,Al2O3颗粒大部分集中在W-M的交界区域,M中钨元素比例减小。SPS循环处理使钨合金达到固溶强化的效果,减小W-W连接度的方法使钨合金获得更高的力学强度。经过更多次SPS循环处理后,钨合金弯曲强度和断裂挠度获得显著改善,在18次SPS循环工况下达到最大。经过多次SPS循环,M内形成更多位错,使合金强度获得较大提升。     

Effect of dissolved tungsten on the deformation of 70Ni-30Fe alloys

A series of Ni-Fe alloys containing various levels of tungsten in solid solution have been prepared as a means to assess the influence of solid solution strengthening on the mechanical behavior of monolithic 70Ni-30Fe. In particular, 70Ni-30Fe alloys plus equilibrium concentrations of tungsten in solid solution nominally correspond to the compositions associated with the matrix-only portion of certain tungsten heavy alloys, that is, alloys comprised of a high volume fraction of nominally pure tungsten particles embedded within a minority Ni-Fe-W based matrix. The study shows that the working solubility of tungsten within the 70Ni-30Fe base composition increases slightly with temperature, from approximately 21 wt pct at room temperature to approximately 23 wt pct at 1400 °C. Increasing the level of tungsten in solid solution leads to increases in room-temperature yield strength, tensile strength, and ductility. In contrast, the deformation characteristics of the alloys, as quantified by the power-law work-hardening exponent, n, and the strain-rate-sensitivity exponent, m, show little variation with tungsten solute concentration.     

Co/Ni比对93W-Co-Ni钨合金烧结温度及力学性能的影响

以Co、Ni作黏结剂,选择不同Co/Ni比,用粉末冶金法制备出HRC硬度在30⁴3之间的93W-Co-Ni钨合金。采用光学金相、扫描电镜对合金组织形貌进行表征,采用准静态拉伸试验对合金的抗拉强度及延伸率进行测试,采用洛氏硬度计对合金硬度进行测定。结果表明:随着Co/Ni比增加,合金的烧结温度逐渐增加,其抗拉强度与延伸率急剧降低,而硬度先增加之后趋于稳定;当Co/Ni≥1.0时,合金抗拉强度很低,延伸率≤1%;当Co/Ni≥4时,其HRC硬度值稳定在4143之间的93W-Co-Ni钨合金。采用光学金相、扫描电镜对合金组织形貌进行表征,采用准静态拉伸试验对合金的抗拉强度及延伸率进行测试,采用洛氏硬度计对合金硬度进行测定。结果表明:随着Co/Ni比增加,合金的烧结温度逐渐增加,其抗拉强度与延伸率急剧降低,而硬度先增加之后趋于稳定;当Co/Ni≥1.0时,合金抗拉强度很低,延伸率≤1%;当Co/Ni≥4时,其HRC硬度值稳定在41⁴3之间,明显高于一般的W-Ni-Fe合金,这主要与Co对W基体的润湿性较差及两者之间易形成脆性化合物Co7W6有关。     

Oxide dispersion strengthened nickel-base heat resistant alloys by means of the spray-dispersion method

The spray-dispersion method, which produces a metal containing homogeneously dispersed fine oxide particles sprayed from outside into the molten metal stream, was applied to HASTELLOY^* X and Ni−Cr−W alloy. The condition of the dispersion of ZrO₂ particles and the mechanical properties were examined for ZrO₂ dispersed alloys. The addition of a dispersion controlling element, Nb or Ta, was found to be effective for decreasing the average particle diameter of sprayed particles and for increasing the volume fraction of the particles. Ultimate tensile strength and 0.2 pct proof strength were increased by ZrO₂ particle dispersion. And creep strength of ZrO₂ particle dispersed alloys was greater than that of non-dispersed ones. From these results, the production of oxide dispersed nickelbase heat resistant alloys has been established by the spray-dispersion method.     

Investigation of deformation and heat treatment effects on properties of PM 92.5W–5Ni–2.5Fe heavy alloys

Abstract

This paper presents the effects of vacuum heat treatment under different cooling conditions on mechanical and structural properties of forged heavy alloys, such as 92.5W–5Ni–2.5Fe and 92.5W–5Ni–25Fe microalloyed with Co. The tungsten composition in the c phase has proved to be higher and more homogenous in the rapidly cooled alloys than in the slowly cooled ones. The effects of chemical composition inhomogeneity on mechanical and structural properties of alloys were also analysed and discussed. The results of tensile and toughness testing have shown an increase in ductility and toughness, while the strength of heat treated alloys decreased in comparison with the strength of forged alloys. The fracture analysis has shown that in the sintered and rotary forged alloys, intergranular fracture of the tungsten phase and transgranular fracture of the γ phase occurred, respectively. The fracture of these phases after heat treatment was characterised by transgranular morphology.     

The relative effects of chromium,molybdenum, tungsten,and tantalum on the occurrence of σ phase in cast Ni-Co-Cr alloys

Chromium, molybdenum, tungsten, and tantalum have been compared with each other in regard to their influence on the occurrence of Σ phase in cast nickel-base superalloys. The compositions of the alloys were similar to the chromium-enriched matrix of alloys strengthened by λ′ precipitate, but with systematic variations in refractory-metal content. To induce precipitation of Σ phase, the alloys were aged for 3000 h at 1400?F (760?C), 1550?F (845?C), and 1700?F (925?C). Quantities of Σ phase were determined with the aid of an image-analyzing computer. On an atomic percentage basis, molybdenum, tungsten, and tantalum are equivalent with regard to the minimum concentration of each element that is necessary to cause Σ phase precipitation in 3000 h; their potency is slightly more than twice as high as that of further chromium additions above the 37.5 at. pct base chromium level. At higher refractory metal concentrations, somewhat greater quantities of Σ phase are formed by specific atomic concentrations of molybdenum and tungsten than by tantalum. Tantalum also forms large quantities of a tantalum-containing Μ phase in the as-cast ingot and a (Ni, Co)₃Ta phase on aging, the volume of all precipitate being much higher than the quantity of Σ phase for the molybdenum- and tungsten-containing alloys. At any given atomic concentration of molybdenum, tungsten, or tantalum, considerably larger quantities of Σ phase are formed than by a given increment of chromium above the 37.5 at. pct base chromium concentration in Mo-W-Ta-free alloys.     

Al1.5Co4Fe2CrCux高熵合金的电磁吸波性能

高熵合金由于其在恶劣环境中的适用性以及对电磁场的多种衰减机制，使其在吸波领域具有巨大的潜在优势和广阔的应用前景。因Cu元素具有优异的延展性和导电性而被广泛应用，添加Cu元素以探究不同Cu含量下Al_1.5Co₄Fe₂CrCu_x (x=0.5, 1.0, 1.5, 2.0；摩尔比)高熵合金的吸波性能。结果表明，通过机械合金化制备的Al_1.5Co₄Fe₂CrCu_x高熵合金为片状、粒状和椭球状，具有软磁特性；饱和磁化强度随着Cu含量的增大逐渐减小，矫顽力则逐渐增大；同时，添加Cu元素有助于形成大长径比的粉末颗粒，调节合金粉末的磁性能和电磁性能，进一步增强合金粉末的介电损耗能力。当x=1.0时，Al_1.5Co₄Fe₂CrCu高熵合金粉末具有最高的衰减系数，在1.50 mm的较薄厚度下其最小反射损耗为-16.50 dB, 1.70 mm厚度下其在Ku波段的有效...     

The influence of cobalt,tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys

The influence of composition on the tensile and creep strength of [001] oriented nickel-base superalloy single crystals at temperatures near 1000 °C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247.* For alloys with the baseline refractory metal level of 3 wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta plus W totals, strength was independent of Co level. The effects of composition on properties were related to the microstructural features of the alloys. In general, high creep strength was associated with high levels ofγ′ volume fraction,γ-γ′ lattice mismatch, and solid solution hardening.     

Microstructure effects on tensile properties of tungsten-Nickel-Iron composites

Controlled processing of heavy alloys containing 88 to 97 pct W resulted in high sintered densities and excellent bonding between the tungsten grains and matrix. For these alloys, deformation and fracture behavior were studiedvia slow strain rate tensile testing at room temperature. The flow stress increased and the fracture strain decreased with increasing tungsten content. The tradeoff between strength and ductility resulted in a maximum in the ultimate tensile strength at 93 pct W. Microstructure variations, notably grain size, explain sintering temperature and time effects on the properties. During tensile testing, cracks formed on the surface of the specimens at tungsten-tungsten grain boundaries. The crack density increased with plastic strain and tungsten content. The surface cracks, though initially blunted by the matrix, eventually increased in density until catastrophic failure occurred. An empirical failure criterion was developed relating fracture to a critical value of the surface crack tip separation distance. Application of the model explains the effects of microstructural variables on tensile properties. Formerly Graduate Research Assistant at Rensselaer Polytechnic Institute.     

大直径钨镧合金锻造棒材性能研究

采用纳米掺杂方法制备了大直径钨镧合金棒坯,通过与纯钨对比,研究了不同氧化镧质量分数的钨镧合金棒坯烧结性能以及含质量分数1.0%纳米氧化镧粉掺杂的钨镧合金锻造棒材的室温性能和高温再结晶性能。结果表明:采用质量分数1.0%、1.5%和2.0%三种含量的纳米氧化镧粉掺杂烧结后,合金掺杂分布和晶粒组织均匀,随着氧化镧含量的增高,棒坯密度逐渐降低、晶粒数逐渐越多;1.0%氧化镧粉掺杂钨镧合金棒坯经过78.7%锻造变形量后,较纯钨棒材硬度值更高,金相组织更细、更均匀,车加工后车削较长,表面光洁度较高,再结晶温度比纯钨高约150℃。     

合金元素Ni对Fe-Cu合金析出过程的影响

以添加Ni前后的Fe-Cu合金和Fe-Cu-Ni合金为研究对象,采用金相显微镜(OM)观察了Fe-Cu合金与Fe-Cu-Ni合金时效过程中的显微组织形貌变化,借助硬度测试分析了两种合金在等温时效过程中的硬度变化规律,并利用透射电子显微技术(TEM)进行了两种合金的析出相精细结构观察与衍射分析,在此基础上,通过实验与理论分析相结合的方法,探索了Ni元素的添加对含铜钢的显微组织、硬度及析出相形貌、尺寸的影响。显微形貌及硬度测试显示,Ni元素的加入提高了钢的淬透性,从而促进了淬火马氏体的形成,合金的强化效果显著增强,硬度与不添加Ni元素的实验钢相比有明显提高;析出相观察发现,含铜钢中Ni元素的加入加快了形核的进程,提高了析出相颗粒的形核的速率,促进富Cu相的析出,从而细化了析出相的尺寸;透射电子衍射分析表明,Cu在时效过程中会发生结构演化,逐渐形成了bcc结构的富Cu亚稳相。