石墨添加量对热压镍铬钼-石墨复合材料性能的影响

本论文研究了热压制备添加石墨的镍铬钼复合材料的力学性能及摩擦磨损特性。结果表明，随着石墨添加量的增加，复合材料的抗拉强度和伸长率逐渐下降，硬度逐渐上升，摩擦系数逐渐变大。其中添加石墨后的复合材料硬度明显高于不添加石墨的基体合金硬度，石墨添加量（质量分数）为1％时复合材料的磨损率最低。新材料中由于添加石墨而形成的硬质碳化物及游离石墨的存在，正是这种力学性能及摩擦磨损变化规律的根本原因。     

钼钨合金的组织和性能研究

本文研究了钼钨合金的粉末制备和烧结工艺,得到了相对密度大于96%且成分组织均匀的钼钨合金。通过对比Mo-50W合金与钨合金的断口形貌和力学性能,得出Mo-50W合金具有比工业生产钨合金更高的致密度和强度。     

二次热压对粉末冶金铍铝合金显微组织与力学性能的影响

研究了二次热压工艺对粉末冶金铍铝合金微观组织和力学性能的影响,并对合金断口形貌进行了分析。结果表明:一次热压铍铝合金,其显微组织中铍相以趋于球状的颗粒分布于连续的铝基体内,合金抗拉强度为230 MPa,屈服强度为157 MPa,延伸率为3.5%;二次热压铍铝合金,其显微组织中铍相边界粗糙,铝相出现晶界且其晶粒趋于圆形,合金抗拉强度提高到304 MPa,屈服强度为253 MPa,延伸率为1.5%。一次热压铍铝合金断口无明显裂纹源,呈均匀的塑性变形,主要以铍相的穿晶解理断裂和铝相的韧性断裂为主;二次热压铍铝合金断口有较为明显的裂纹源,除了发生铝相的塑性变形断裂和少量的铍相解理断裂外,铍铝相界同时发生了开裂。     

氧化锆对钼金属组织和性能的影响

通过对MZO合金与纯钼断口形貌和力学性能的测试分析,研究了添加ZrO_2对钼金属的组织和性能的影响。结果表明:添加ZrO_2使钼的烧结进程延迟;ZrO_2颗粒明显抑制了钼颗粒长大,最终获得晶粒组织细小,第二相均匀分布的钼合金,这使得MZO合金比纯钼具有更高的室温强度与延伸率。     

高含量La_2O_3/Y_2O_3对钼合金微观组织与性能的影响

采用粉末冶金方法制备了不同质量分数La_2O_3/Y_2O_3复合稀土氧化物掺杂的钼合金,观察了钼合金物相构成、显微组织和断口形貌,测试了其力学性能。结果表明:掺杂La-2O_3/Y_2O_3钼合金的物相组成为La_2O_3、Y_2O_3和Mo;锻造态钼合金横截面的晶粒尺寸随La_2O_3/Y_2O_3含量增加而减小,锻造态钼合金纵截面的显微组织为明显的纤维状织构组织形态;锻造态Mo(La_2O_3)3.0(Y_2O_3)0.5钼合金的横截面断口为韧窝断裂和少量解理断裂,纵截面断口为沿晶脆性断裂;合金抗弯强度和弯曲角随La_2O_3/Y_2O_3含量的增加先增加后降低,Mo(La_2O_3)3.0(Y_2O_3)0.5钼合金抗弯强度达到1133 MPa,弯曲角达到38°。     

W-Ni-Fe高比重合金断口形貌研究

通过对W-Ni-Fe高比重合金力学性能差别很大的两组断口形貌进行分析,在一些高比重合金钨颗粒内发现有W-Ni-Fe的沉淀相,该沉淀相对合金力学性能的提高有益。沉淀相形成主要与成分配比以及烧结后期的真空处理有关。断口形貌可以反应高比重钨合金的烧结状况,而材料的力学性能与合金断口形貌又有很明显的对应关系,因此,要获得很高的力学性能,烧结及热处理工艺是十分重要的工序。     

不同固-固掺杂工艺对氧化锆弥散强化钼合金性能的影响

以氧化锆作为添加剂,采用粉末冶金法分别在二氧化钼和钼粉中固-固掺杂制备出了氧化锆弥散强化钼合金。分析对比了合金金相组织及微观结构的差异,并测试了不同掺杂工艺制备出的钼锆合金的抗拉强度、硬度以及再结晶温度。试验表明：采用不同的固-固掺杂工艺制备出的钼锆合金在力学性能、加工性能以及再结晶温度方面存在一定差异。在二氧化钼中掺杂氧化锆制备的钼锆合金经过一定程度塑性加工之后硬度、抗拉强度更高,加工硬化现象更明显,加工至?0.68 mm丝材的再结晶温度约为1 400℃,比相同条件下在钼粉中添加氧化锆制备的钼锆合金再结晶温度提高约200℃左右,具备更好的高温力学性能。     

钼铼合金带材的组织和性能

选用熔炼的钼铼合金经过锻造、热拉、冷拉和轧制的方法制备钼铼合金带材，其规格为0．3mm宽0．03mm厚，对其组织和性能进行了研究。结果表明：加工态的拉断力是再结晶状态的2．5倍左右，为24．8N；而延伸率只是再结晶状态的1，3，为3．1％；随着退火温度的提高，钼铼合金的的拉断力直线降低，但延伸率在1723K，30min退火后却最高，金相结果表明1723K退火的钼铼合金带材发生了明显的再结晶。钼铼合金加工态拉伸时其断口表现为准解理断裂，退火后断口表现为明显的韧窝状。铼元素加入钼中，可以提高晶粒和晶粒之间的结合力，使得钼铼合金在拉伸下有很好的延伸率。同时钼铼合金在室温变形时，也容易发生孪晶变形，这一点不同于通常的钼合金。     

钼合金粉末冶金研究进展

钼及其合金具有优异的高温力学性能，被广泛应用于冶金、机械、化工、航空和核工业等领域。粉末冶金是钼合金的主要制备方法。通过固溶强化、第二相强化、细晶强化等多种强化手段可以提高钼合金的力学性能，从而拓宽钼合金的应用范围。本文介绍了粉末冶金制备钼合金的研究进展，包括粉体制备方法、压制工艺及坯体烧结工艺等，讨论了钼合金的强韧化方法及其机理，并展望了粉末冶金法制备钼合金的发展方向，以期对钼合金的设计和制备提供一些思路。     

粉末粒度对发动机钼护板力学性能的影响

通过对由不同费氏粒度的钼粉粉末制备的钼护板,在工作时间60 s的固体火箭地面发动机试车试验进行测试,通过对烧蚀结果的金相组织、力学性能测试、断口组织分析,获得了粉末粒度与钼护板力学性能的相关性。结果表明:对于工作时间60 s的固体火箭发动机中搭载使用的钼护板,随着原始粉末粒度的增大,抗烧蚀效果相应提高,力学性能表现也越好。     

Magnetic Alignment Study of Hybrid Magnet Consisting of R-Rich and R-Lean Nd-Fe-B Alloys

A hybrid magnet was prepared by the hot-pressing and die-upsetting of the mixture of the R-rich Nd_xFe_93.5–xGa_0.5B₆ (x= 13.5 and 11.8) alloy and the R-lean Nd_xFe_93–xNb₁B₆ (x = 6, 9) alloy melt-spun ribbons. The microstructure and magnetic properties of the hybrid magnet were investigated. In the hot-pressed or die-upset hybrid magnet the R-rich and R-lean alloy regions existed independently without alloying between them. The two alloy regions in the die-upset hybrid magnet were coupled effectively via a magnetostatic interaction. A texture was developed only in the R-rich Nd₂Fe₁₄B single phase alloy region in the die-upset hybrid magnet, and this led to an anisotropic nature in die-upset hybrid magnet. The die-upset hybrid magnets containing higher Nd-content (13.5 at%) host alloy shows consistently a better magnetic alignment with respect to the magnets with lower Nd-content (11.8 at%) host alloy.     

Development of a Technology for the Production of Tubes from Ni ― Mo Alloy Powder

Technology for the production of tubes from mixtures of nickel and molybdenum powders by hot pressing and cold rolling was developed. The operational parameters for hot pressing were determined and the engineering and mechanical properties of the tubes studied. The effect of annealing temperature on the mechanical properties of the hot-pressed metal was investigated. Regimes for cold rolling the hot-pressed tubes in rolling mills were determined. The rolled tubes were tested in accordance with the accepted specifications for alloy ÉP982. All tubes passed the engineering tests; the mechanical properties of the tube metal are superior to those of alloy ÉP982. The proposed technology is quite economical, the yield of satisfactory product is 80-85%.     

Structure and mechanical properties of ingots and rolled sections of aluminum alloy based on the Al-Mg-Mn system

Commercial ingots and hot-pressed rolled sections of Al-Mg-Mn alloy doped with zinc, scandium, zirconium, chromium, and vanadium have been studied using optical microscopy, thermal analysis, electron microscopy, and electron-probe microanalysis. The compositions of the phase constituents and aluminum matrix of the alloy are determined. The sensitivity of the alloy to the formation of complex intermetallic compounds during solidification is revealed. The mechanical properties of ingots and rolled sections are determined.     

低温球磨法制备块体纳米晶Al-Zn-Mg-Cu系铝合金

采用低温球磨法制备了纳米晶Al—Zn—Mg—Cu系铝合金粉末，对纳米晶粉末进行真空热压，获得纳米晶铝合金块体。采用显微分析方法研究了纳米晶粉末和块体材料的微观组织结构：试验结果表明，纳米晶铝合金粉末具有良好的热稳定性，热压块体的平均晶粒尺寸在100nm以下。低温球磨所得铝合金粉末晶粒尺寸为48nm；真空退火试验表明其具有良好的热稳定性；热压块体的平均晶粒尺寸在100nm以下。     

真空热压技术在制备CuCr合金中的应用研究

采用真空热压新技术制造了高密度CuCr50合金，并与冷压成型技术进行了比较，分析了两种工艺合金的相对密度变化及显微组织，研究了真空热压工艺的致密化机理。     

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。     

The Effect of Twins on the Mechanical Behavior of Boron Carbide

The microstructure and mechanical properties of boron carbide (B₄C) samples processed by slip casting were compared with those processed by the conventional hot-pressing technique. Although the quasi-static and dynamic mechanical experiments showed comparable results between the slip-cast and hot-pressed B₄C, scanning electron microscopy and electron backscattered diffraction of the B₄C samples revealed significant differences in the microstructure. A notable difference was the numerous growth twins in the slip-cast samples. The twin planes were determined to be { 10[`1] 1 } \left\{ { 10\bar{1} 1} \right\} and consisted of 35 pct of the boundary population in the slip-cast B₄C but only 1 pct of the boundary population in the hot-pressed B₄C. It was hypothesized that the presence of twins will cause a different failure mechanism. The effect of the twins on the stress state was examined by finite-element simulations and will also be discussed.     

FURTHER DEVELOPMENTS IN METAL-GRAPHITE BEARING MATERIALS

Abstract

From the earliest incorporation of graphite with metal oxides or metal powders to form porous bearings of low mechanical strength, progressive improvements led to the production of intentionally non-porous graphited metal bearings containing relatively high volumes of finely distributed graphite. These higher-strength bearing materials were achieved in the middle of this century by the employment of hot-pressing techniques.

The latest development in this range of materials has seen a reversion to methods of double cold pressing and sintering, which have been facilitated by the enhanced ductility gained from modifications to composition and microstructure. The resultant bearings are produced to finished dimensions without machining, thus affording economies over hot-pressed materials.

Some details regarding the properties of such bearings are given and typical applications are described.     

热压烧结法制备石墨/铜铬自润滑复合材料的组织性能

将机械合金化所制得的铜铬合金粉末,采用热压烧结法制备成石墨/铜铬复合材料,并着重分析了其组织性能。结果表明,随着铬含量的增加,复合材料的相对密度和电导率逐渐降低,硬度逐渐升高,抗弯强度先升后降且于铬含量为1%时达到最大。其中含1%Cr和2%C复合材料的相对密度为99.82%,电导率为85.57%IACS,硬度为HBS 69.34,抗弯强度为330MPa。与常规冷压烧结法相比,热压烧结法所制备复合材料的晶粒更加细小,增强相分布更加均匀,故其综合性能更加优异。     

喷射沉积Al-12Si-0.6Mg合金的微观组织与性能

共晶合金具有良好的激光焊接性能,为提高电子封装盖板用Al-12Si合金的强度并保持良好的热物理性能,采用喷射沉积与热压烧结技术制备Al-12Si合金,研究添加0.6% Mg对合金微观组织、力学性能和热物理性能的影响。结果表明,喷射沉积/热压烧结Al-12Si合金中Si相呈近球形颗粒,平均直径为（4.5±0.2）μm,均匀分布于Al基体中;添加Mg未对Si相尺寸和形貌产生显著影响,但是在Al基体中形成Mg₂Si相。相对于Al-12Si合金,Al-12Si-0.6Mg合金的热导率降幅仅为4.2%,但是抗拉强度从154.1 MPa提高到190.1 MPa,增幅达到23.4%,该强度改善主要归因于固溶强化和析出强化作用。