热压温度对真空热压法制备Cu–30Ni–5Nb合金组织及性能的影响

采用真空热压法制备了Cu–30Ni–5Nb合金,研究了热压温度对合金组织、相对密度、熔点及热导率的影响。结果表明,在800～950 ℃热压温度范围内,Cu–30Ni–5Nb合金的熔点先降低后升高,900 ℃时铜合金的熔点最低（1178.92 ℃）;Cu–30Ni–5Nb合金的热导率先增大后减小,900 ℃时铜合金的热导率最大（30.65 W·m?1·K?1）。热压温度为875 ℃时,Cu–30Ni–5Nb合金具有较好的综合性能,相对密度为98.66%,熔点为1180.86 ℃,热导率为29.54 W·m?1·K?1,且合金屈服强度达到355.74 MPa,符合冷却水套的性能要求。     

热等静压烧结温度对Mo–Na合金性能影响

采用热等静压烧结法制备Mo–Na合金，研究了热等静压烧结温度对Mo–Na合金显微组织、硬度、密度及Na质量分数的影响，分析了Mo–Na合金热等静压烧结的致密化过程。结果表明:采用热等静压烧结法制备的Mo–Na合金显微组织细小均匀，平均晶粒尺寸在10 μm以下。随着热等静压烧结温度的升高，相对密度及硬度随之升高，在1100 ℃时达到最大，分别为99.58%和HRA 54.50，热等静压过程中液相的形成对Mo–Na合金的致密化起到了重要作用。热等静压过程很好地避免了低熔点Na金属高温烧结过程中的挥发，在1100 ℃烧结后Na质量分数基本无变化。     

细晶W-15Cu材料的制备研究

利用机械合金化工艺制备了颗粒尺寸为0．5μm、W晶粒尺寸为10am的纳米晶W-Cu粉末，研究了其烧结致密化行为、烧结合金显微组织及其性能，并考察了其晶粒长大特性。结果表明：烧结温度和时间的增加有利于致密化，1300℃烧结30min，合金取得了99％的相对密度；硬度随烧结温度、时间的增加而增加，在1375℃烧结30min，硬度为HB321。W晶粒随着烧结温度的升高而增大，1200℃烧结30min获得了相对密度为98％以上、硬度为HB264、晶粒尺寸约为350am的细晶W-Cu合金。     

烧结方法对WC-Co硬质合金性能的影响

以原位还原碳化反应法制备的超细WC-Co复合粉为原料,分别采用放电等离子烧结、低压烧结和真空烧结工艺获得块体硬质合金,系统研究烧结方法对合金的显微组织、密度及力学性能的影响。结果表明:放电等离子烧结的合金中,主相为WC和Co,有少量η相(Co6W6C),低压烧结和真空烧结获得的合金中物相为WC和Co;所用3种不同的烧结方法均能获得细晶块体硬质合金,其中放电等离子烧结的晶粒最细为0.35μm;低压烧结合金具有优异的综合性能,HV30为15 121 MPa,断裂韧性为13.6 MPa.m1/2,横向断裂强度为4 210 MPa。     

烧结温度对Ni-Cr-Mo合金性能的影响

Ni-Cr-Mo合金经冷压成型后于真空中以不同温度进行烧结。通过测定其相对密度、线收缩 率、拉伸强度和硬度,研究烧结温度对合金性能的影响。研究结果表明:当烧结温度不超过1330 ℃时,合金的相对密度、收缩率、拉伸强度和硬度随烧结温度的上升而缓慢增加;当温度上升到 1360℃时,合金的这些性能指标急剧增大;当温度上升到1390℃时,烧结后的合金试样外形发生 严重变形。     

钌金属溅射靶材烧结工艺研究

采用热压、放电等离子烧结及直接热压等粉末冶金工艺制备了钌金属溅射靶材,通过对致密度、晶粒度与氧含量分析研究了工艺过程对钌金属靶材制备的影响,并对比分析了三种方法制备钌靶的特点。结果表明:通过工艺优化利用三种方法均能制备出相对密度达到99%以上的高密度钌靶;随着制备温度的升高,钌靶氧含量降低,晶粒尺寸增大;热压工艺制备周期最长,钌靶表面有晶粒粗大层;放电等离子烧结与直接热压工艺都具有快速、近净成形的特点。     

烧结温度对W/Mo双金属材料显微组织及力学性能的影响

本文首先通过粉末冶金技术,采用不同的真空烧结工艺制备出W/Mo双金属材料,然后对其显微组织、密度、硬度和结合状态进行了测试。结果表明:将W粉、Mo粉铺层以485MPa的压力冷压成形后,在1600℃、10-3 Pa真空度下烧结2～4h可以制得满足一定条件的W/Mo双金属材料。该W/Mo双金属材料的性能受烧结温度的影响,烧结温度越高得到的W/Mo双金属的密度、强度越高,结合面越平整。     

不同制备工艺对Mo-Mo3Si-Mo5SiR2(T2)三相合金组织的影响

分别采用传统粉末冶金法(PM)和放电等离子烧结(SPS)工艺成功制备了两种Mo-Mo3Si-Mo5SiB2(T2)三相合金.研究了烧结温度等因素对样品相对密度、组成相的影响;同时也比较了两种不同工艺制备的合金在组织等方面的差异.结果表明:通过放电等离子烧结法制备的合金具有较高的相对密度,孔隙小,α-Mo相紧密相连且分布均匀,但含有少量的MoB、Mo2相;而采用传统粉末冶金法制备的合金具有较大的孔隙,相对密度较低.     

烧结参数对羰基铁粉放电等离子烧结的影响

采用放电等离子烧结技术烧结羰基铁粉,研究烧结温度和保温时间对烧结致密度、硬度及晶粒尺寸的影响.结果表明:当烧结温度为600℃时,烧结体的相对密度达到95%以上;而当烧结温度超过600℃时,烧结体密度几乎不再发生变化.同时发现保温时间对烧结体的相对密度影响不大,但硬度随保温时间的延长而增大.烧结体的晶粒尺寸随烧结温度的升高和保温时间的延长而长大,但是长大的幅度较小,与原始粉末的粒度在同一数量级.     

粉末冶金法制备Ta–W–Si合金

采用热压烧结和放电等离子烧结的方法制备了Ta–W–Si合金,利用X射线衍射分析、扫描电子显微镜观察、背散射电子成像及能谱分析等手段研究了合金的显微结构和相组成,并讨论了烧结方式和硅质量分数对合金烧结致密化和硬度的影响。结果表明,两种烧结方式烧结后的样品相对密度均达到了96%以上,可以实现致密化,硅元素的添加有利于合金的致密化;扫描电子显微观察和背散射电子成像显示合金中出现两种不同区域,物相分析存在Ta–W与Ta_3Si两相;硅元素的添加有利于提高合金硬度,硅化物第二相强化、细晶强化和晶界区的氧化富集是强化的主要机制。     

W–Re/石墨复合材料的制备、微观组织及性能

以W–Re片和石墨块为原料,Mo/Zr混合粉为焊料,在1850 ℃和30 MPa的条件下通过真空热压烧结制备了W–Re/石墨复合材料,对复合材料的微观组织、剪切断口及室温剪切性能进行了分析。研究结果表明,在热压烧结复合材料的Mo/Zr焊料层中发生了明显的分层现象,靠近石墨区域的物相组成是ZrC和Mo₂Zr,靠近W–Re区域的物相组成是Mo₂Zr和锆基固溶体（Zrss）。复合材料的断裂主要发生在焊料与石墨界面上,焊料并未明显渗透到石墨中,未能形成钉扎作用,试样的室温剪切强度约5 MPa。     

超细钼铜复合粉体及细晶钼铜合金的制备

采用“缺碳预还原+氢气深脱氧”方法制备了不同Cu含量（5%、20%、40%,质量分数）的超细Mo–Cu复合粉末。通过高温煅烧钼酸铵和硝酸铜混合物制备了MoO₃和CuO复合氧化物,再利用炭黑预还原脱除煅烧产物（CuMoO₄–MoO₃）中绝大部分氧的方法制备了含有少量MoO₂的超细预还原Mo–Cu复合粉体;少量MoO₂的存在可以极大降低预还原产物中碳的残留;最后,经氢还原脱除残留的氧制备得到超细、高纯度Mo–Cu复合粉体,粉体粒度约为200 nm。以Mo–Cu复合粉体为原料,经过压坯和烧结制备得到细晶Mo–Cu合金。结果表明,经过1200 ℃烧结后,随着Cu质量分数由5%增加到20%,合金相对密度由96.3%增加到98.5%,且Mo、Cu两相分布均匀。Mo–Cu合金硬度随Cu含量的增加而先增加后降低,这是由合金相对密度和铜含量对硬度的影响不同所导致的。随着Cu质量分数由5%增加到40%,Mo–Cu合金的热导率由48.5 W·m?1·K?1增加到187.2 W·m?1·K?1,电导率由18.79% IACS增加到49.48% IACS。     

W质量分数对Mo-W合金组织结构与力学性能的影响

采用粉末冶金法制备含不同质量分数W(20%~80%)的Mo-W合金, 研究W含量对Mo-W合金组织结构与力学性能的影响。结果表明: 烧结过程中Mo与W相互扩散形成单相固溶体。W质量分数的增加能显著降低Mo-W合金的晶粒尺寸, 经1990℃烧结的Mo-80W合金晶粒尺寸比Mo-20W合金下降了46.5%。随W质量分数的增加, Mo-W合金的维氏硬度呈“双驼峰”形变化趋势, 在W质量分数为40%与60%处出现峰值。Mo-W合金的相对密度和抗拉强度随W质量分数的增加而下降, 抗拉强度最大值出现在烧结温度为1990℃的Mo-20W合金, 达到514.83 MPa; 随烧结温度的升高, 低W含量的Mo-W合金(W质量分数20%~40%)抗拉强度呈先上升后下降趋势, 而高W含量的Mo-W合金(W质量分数60%~80%)抗拉强度逐渐升高。Mo-W合金断裂方式为沿晶断裂与穿晶断裂相结合的混合模式。     

Sintering of very fine molybdenum and tungsten powders

Conclusions Vacuum annealing at a temperature above 900°K enables the specific surfaces of very fine loose tungsten and molybdenum powders to be varied in a wide range. The vacuum sintering of compacts pressed from very fine (particle size less than 0.05m tungsten and molybdenum powders is accompanied by severe cracking. In the hot pressing of very fine Mo and W powders produced by the pyrolysis of carbonyls in a stream of high-temperature plasma, a specimen density close to theoretical is reached at 1600°K i.e., at a temperature not less than 400°K lower than the sintering temperatures of powders of particle size more than 1 m. Sintering lowers the amounts of carbon and oxygen in Mo and W by more than half compared with the starting condition.Translated from Poroshkovaya Metallurgiya, No. 1(229), pp. 47–51, January, 1982.     

Spark plasma sintering versus hot pressing – densification,bending strength,microstructure, and tribological properties of Ti5Al2.5Fe alloys

Ti5Al2.5Fe alloys were fabricated by the spark plasma sintering (SPS) and hot pressing (HP) pressure-assisted sintering techniques from pre-alloyed powders with a particle size of about 200?μm. The powders were sintered at 850 °C for two different holding times (5 and 8 min) and heating rates (50 and 150°C?min^?1) at 25?MPa. The maximum relative densities were 99.70 and 98.78% for SPS and HP samples, respectively. All the alloys prepared by the SPS process had significantly higher bending strengths (1825–2074?MPa) than the alloys prepared by the HP process (648–1330?MPa). A decrease in the heating rate from 150 to 50°C min^?1 enhanced the wear resistance of the Ti5Al2.5Fe alloys prepared by both the SPS and HP processes.     

Structure and hot hardness of RuAl-based alloys produced by reactive sintering using hot isostatic pressing

The structure and hot hardness (at temperatures up to 1100°C) of RuAl-based powder alloys with 1–3 at % Ni, Mo, Re, or Ru are studied. The alloys are produced by the reactive sintering of cold-compacted bars and subsequent threefold isostatic pressing with intermediate annealing at 1500°C performed after the first hot isostatic pressing. The samples have a residual pore content of 1–2.5 vol % and are characterized by a micrononuniform distribution of base and alloying elements. The alloys with refractory metals, such as Re, Mo, or Ru, are found to have the maximum hardness at all temperatures under study. At low temperatures, the effect is more substantial; the hardness of the Re-containing alloys exceeds that of the other alloys by a factor of 1.3–3.6. The increase in the hardness related to solid-solution alloying becomes more substantial owing to the microinhomogeneity of the sintered powder alloys and weakens because of microporosity. Recommendations that allow the uniformity of the distribution of the base and alloying elements to be increased are given.     

Theory and technology of sintering, thermal and chemicothermal treatment

The studies on the densification of WC-Co alloys in solid-phase sintering are analyzed. It is shown that solid-phase sintering of alloys with tungsten carbide particles smaller than 2.0 µm is characterized by high densification (shrinkage) and results in compact samples in some cases. Shrinkage is established to be nonmonotonic over a wide range of sintering temperatures. There are at least three different stages of densification over the range from room to solidus temperatures. Approximate temperature ranges for densification stages are 100 to 1050 °C, 1050 to 1200 °C, and 1200 °C to the eutectic melting temperature. The stages mainly differ in the extent and rate of shrinkage and in the activation energy. The compaction stages are separated by characteristic temperatures. The most important is 1200 °C, which separates the second and the third stages. The maximum rate of shrinkage is observed mostly at this temperature. The variation of initial WC particles from 5 to 2000 nm does not significantly affect the temperature at which the solid-phase shrinkage rate is maximum. In most cases, there are two maximum rates of shrinkage in WC-Co sintering: one at 1200 ± 30 °C and the other at the solidus temperature.     

TiB2对Ta-W合金氧化行为的影响

采用热压烧结制备Ta-W合金和Ta-W-TiB₂合金,研究两种合金在700、800和900℃的高温氧化行为,通过X射线衍射分析、扫描电子显微镜观察和能谱分析对合金的氧化层组分和组织形貌进行分析。结果表明:两种合金经热压烧结后的相对密度均达到97%以上,可以实现致密化。在氧化温度范围内所有合金的氧化动力学曲线都遵循直线规律,氧化温度升高氧化速率逐渐增大。Ta-W合金的氧化产物为Ta₂O₅固溶体,Ta-W-TiB₂合金的氧化产物为Ta₂O₅固溶体和TiO₂氧化物。在700~800℃下,稳定的TiO₂提高了Ta-W-TiB₂合金的抗氧化能力,但在900℃时,TiO₂的破坏大大减弱了氧化层对基体的保护能力。