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采用固相烧结工艺(1 300℃保温1 h)制备低钨含量(质量分数为60%~80%)的W-Ni-Fe合金,测定合金的抗拉强度、抗压强度和伸长率,利用金相显微镜观察合金的显微组织,并通过扫描电镜(SEM)观察合金断口形貌,研究钨含量对固相烧结W-Ni-Fe合金力学性能与微观结构的影响。结果表明:随钨含量降低,合金的孔隙率和平均孔径减小,抗拉强度增大,伸长率显著提高,抗压强度变化不大。W含量为60%~80%的W-Ni-Fe合金,其孔隙率为17.8%~21.4%,抗拉强度为231~262 MPa,抗压强度2 450~2 550 MPa,伸长率为0.3%~2.3%,压拉比为9.45~11.04,都能满足易碎型穿甲弹弹芯材料的性能要求。 相似文献
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以93W-4.9Ni-2.1Fe高比重钨合金为研究对象,系统研究了不同粒度钨粉制备的93W-4.9Ni-2.1Fe合金在1 415~1 550℃温度下烧结后的力学性能,并分析了热处理工艺对钨合金力学性能的影响及钨合金的断裂行为。结果表明:随着烧结温度的升高,烧结态钨合金的力学性能均表现为先增大后减小再增大的规律,在1500~1 510℃烧结时钨合金的力学性能出现突然下降;6.0μm粗钨粉制备的钨合金的力学性能整体比相同烧结温度下细钨粉制备的钨合金高;93W-4.9Ni-2.1Fe合金在氢气气氛中高温烧结后再在氮气气氛下进行固溶+淬火热处理可以显著提高力学性能;钨合金的力学性能与其断裂行为有关,断口形貌为钨晶粒高度的穿晶解理断裂和粘结相延性断裂时合金表现为高强韧性。 相似文献
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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。 相似文献
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研究了W-Ni-Fe高比重合金烧结时的致密化,实验证明W-Ni-Fe合金烧结时的致密化过程具有液相烧结的特征,符合Kingery提出的方程。目前生产的W-Ni-Fe合金中粘结相常采用Ni:Fe=7:3或Ni:Fe=1:1。针对这两种成分的合金我们研究了不同温度下的收缩率、密度变化与时间的关系,并讨论了其致密化机理。 相似文献
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用金相分析,X射线衍射相分析和透射电镜观察等手段,全面细致地考察了液相烧结W-Ni-Fe合金的微观组织。发现90%W-Ni-Fe合金中,只要有少量的碳存在,在液相烧结后缓慢冷却的条件下将有析出相产生,经物理化学方法分析鉴定,它是η′类型(A_6B_6C型)碳化物,其结构属于复杂立方晶系(f.c.c.晶格),晶格常数为10.935,其化学组成式可近似写成(Ni,Fe)_6W_6C,其形貌随着冷却速度大小而变化。合金力学性能检验和断口扫描观察的结果证明,此析出相在合金中是脆性相,它严重地降低合金的强度和塑性。通过各种热处理试验,找出了其成因,并制定了避免其产生和将其消除的措施。考虑了快冷与缓冷各自的利弊,为W-Ni-Fe合金的生产提出了一个较合理的制度。 相似文献
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本文讨论了W-7Ni-3Fe钨合金微结构、断口特征和力学性能的关系。用扫描电镜观察了断口表面,指出力学性能对应的W-7Ni-3Fe合金断口形貌特征。用电子探针微区分析仪进行了元素分析,表明钨合金的强度与强化相的形状、尺寸以及分布状态等参数有密切关系。也讨论了真空退火的影响。 相似文献
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研究了烧结态和真至热处理态高比重合金(95W-3.5Ni-1.5Fe)的断裂韧性KIc和动态断裂韧性KId以及断裂试样断口的微观形貌。结果表明,真空处理合金的室温拉伸强度和延伸率大幅度增加,KIC和KId随之提高。由于合金对加荷速率敏感,真空处理态和烧结态合金的断裂韧性值比动态断裂韧性值高,因此合金在动态条件下使用时,以KId值去确定a的尺寸才安全可靠。同时,真空脱氢,使钨颗粒相和粘结相界面结合力加强,结果真空热处理试样的KIC和KId断口的解理面增加。加荷速率增加导致动态断裂韧性试样断口的解理面比KIc试样增多。 相似文献
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纳米晶钨合金粉末常压烧结的致密化和晶粒长大 总被引:3,自引:1,他引:2
高比重合金由于具有密度和强度高、延性好等一系列优异的性能,在军工上被用作动能穿甲弹材料.纳米材料被认为是21世纪应用前景最为广阔的新型材料.采用纳米粉末可望大大细化钨合金晶粒,显著提高合金的强度、延性和硬度等力学性能,因而是制备新型高强韧、高比重钨合金的一个很重要的研究方向.作者采用机械合金化(MA)工艺制备了纳米晶钨合金复合粉末,研究了纳米晶钨合金粉末在常压氢气气氛中的烧结致密化和在烧结过程中的钨晶粒长大行为.研究结果表明,MA纳米晶粉末促进了致密化,使致密化温度降低约100~200℃.在一般固相烧结温度时可以得到晶粒尺寸为3~5μm的细晶高强度合金.同时,指出了在液相烧结时存在的问题,即钨晶粒加速重排、产生晶粒聚集与合并,迅速发生钨晶粒长大,在较短时间内液相烧结时,钨晶粒尺寸又长大到接近传统高比重合金水平. 相似文献
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Dynamic deformation behavior of an oxide-dispersed tungsten heavy alloy fabricated by mechanical alloying 总被引:14,自引:0,他引:14
Sanghyun Park Dong-Kuk Kim Sunghak Lee Dong-Kuk Kim Ho Jin Ryu Soon Hyung Hong Ho Jin Ryu 《Metallurgical and Materials Transactions A》2001,32(8):2011-2020
The objective of this study is to investigate the dynamic deformation and fracture behavior of an oxide-dispersed (OD) tungsten
heavy alloy fabricated by mechanical alloying (MA). The tungsten alloy was processed by adding 0.1 wt pct Y2O3 powders during MA, in order to form fine oxides at triple junctions of tungsten particles or at tungsten/matrix interfaces.
Dynamic torsion tests were conducted for this alloy, and the test data were compared with those of a conventional liquid-phase
sintered (LPS) specimen. A refinement in tungsten particle size could be obtained after MA and multistep heat treatment without
an increase in the interfacial area fraction between tungsten particles. The dynamic test results indicated that interfacial
debonding between tungsten particles occurred over broad deformed areas in this alloy, suggesting the possibility of adiabatic
shear-band formation. Also, oxide dispersion was effective in promoting interfacial debonding, since the fine oxides acted
as initiation sites for interfacial debonding. These findings suggest that the idea of forming fine oxides would be useful
for improving self-sharpening and penetration performance in tungsten heavy alloys. 相似文献
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Effect of tungsten particle shape on dynamic deformation and fracture behavior of tungsten heavy alloys 总被引:1,自引:0,他引:1
Dong-Kuk Kim Sunghak Lee Heungsub Song 《Metallurgical and Materials Transactions A》1998,29(3):1057-1069
The effect of the tungsten particle shape on the dynamic deformation and fracture behavior of tungsten heavy alloys was investigated.
Dynamic torsional tests were conducted using a torsional Kolsky bar for five alloys, one of which was fabricated by the double-cycled
sintering process, and then the test data were compared via microstructures, mechanical properties, adiabatic shear banding, and fracture mode. The dynamic torsional test results indicated
that in the double-sintered tungsten alloy whose tungsten particles were very coarse and irregularly shaped, cleavage fracture
occurred in the central area of the gage section with little shear deformation, whereas shear deformation was concentrated
in the central area of the gage section in the other alloys. The deformation and fracture behavior of the double-sintered
alloy correlated well with the observation of the impacted penetrator specimen and the in situ fracture test results, i.e., microcrack initiation at coarse tungsten particles and cleavage crack propagation through tungsten particles. These findings
suggested that the cleavage fracture mode would be beneficial for the self-sharpening effect, and, thus, the improvement of
the penetration performance of the double-sintered tungsten heavy alloy would be expected. 相似文献
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Dong-Kuk Kim Sunghak Lee Heung-Sub Song 《Metallurgical and Materials Transactions A》1998,29(13):1057-1069
The effect of the tungsten particle shape on the dynamic deformation and fracture behavior of tungsten heavy alloys was investigated.
Dynamic torsional tests were conducted using a torsional Kolsky bar for five alloys, one of which was fabricated by the double-cycled
sintering process, and then the test data were compared via microstructures, mechanical properties, adiabatic shear banding, and fracture mode. The dynamic torsional test results indicated
that in the double-sintered tungsten alloy whose tungsten particles were very coarse and irregularly shaped, cleavage fracture
occurred in the central area of the gage section with little shear deformation, whereas shear deformation was concentrated
in the central area of the gage section in the other alloys. The deformation and fracture behavior of the double-sintered
alloy correlated well with the observation of the impacted penetrator specimen and the in situ fracture test results, i.e., microcrack initiation at coarse tungsten particles and cleavage crack propagation through tungsten particles. These findings
suggested that the cleavage fracture mode would be beneficial for the self-sharpening effect, and, thus, the improvement of
the penetration performance of the double-sintered tungsten heavy alloy would be expected. 相似文献
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高密度钨合金研究的新进展 总被引:2,自引:1,他引:1
从原材料、烧结工艺及其后处理、强韧化和杂质对高密度钨合金的影响等方面介绍了国内外近10年来在高密度钨合金领域所取得的进展,并从这些方面详细讨论了影响高密度钨合金性能的具体因素。此外,提出了钨合金今后的发展方向。 相似文献
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Liquid phase sintered tungsten heavy alloy specimens with a 90W-7Ni-3Fe composition were tested for temperature and strain
rate effects on mechanical behavior. Both fracture stress and strain were measured for samples tested at 20, 300, or 600 °C,
with crosshead speeds ranging from 0.004 to 400 mmJs in an argon atmosphere. Fracture surface examinations showed a dramatic
increase in tungsten cleavage as the ductility increased. The effect of an increasing strain rate is a slight strength increase
with a concomitant ductility decrease. Alternatively, higher test temperatures degrade strength with a nonsystematic effect
on ductility; maximum ductility occurs at 300 °C and a slow strain rate. Surface oxidation at 600 °C greatly degrades ductility.
The results are mathematically modeled using classic strain rate dependent equations. 相似文献
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U. Ravi Kiran M. Sankaranarayana G. V. S. Nageswara Rao T. K. Nandy 《Transactions of the Indian Institute of Metals》2017,70(3):615-622
The present investigation attempts to study the microstructure and mechanical behaviour of tungsten heavy alloys with different cobalt content. Alloys with 2 and 3% cobalt were synthesized using liquid phase sintering technique. The alloys were then vacuum heat treated and finally swaged. Quantitative microstructural analyses were undertaken by determining tungsten grain size, contiguity of tungsten and volume fraction of the matrix etc. Tensile results showed that the alloy with 3% cobalt exhibited inferior properties as compared to 2% cobalt alloy. Detailed microstructural and fractographic analysis were undertaken in order to understand these trends. Work hardening analysis showed the double slope behaviour of the alloys, which could be attributed to change in deformation behaviour from single phase matrix to two phase aggregate. It was also concluded that higher cobalt alloys needed further optimization in terms of thermo-mechanical treatment in order to realize their full potential in terms of mechanical properties. 相似文献
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《粉末冶金学》2013,56(2):191-199
AbstractThis 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. 相似文献
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研究了注射成形高比重合金的致密化和变形行为,实验表明在液相烧结过程中,由于重力的作用导致粘性流动,样品发生变形,对W含量较高的合金,采用2步烧结工艺可以有效地控制变形,在此工艺中,压坯首先在粘结相熔点温度以下烧结,形成W连通骨架,然后在高于粘结相熔点以上的温度下烧结较短时间以达到全致密,对于W含量较低的高比重合金,将原始混合粉末采用机械合金化,然后再进行固相烧结,可以得到性能很好的无变形合金。 相似文献