Spark plasma sintering on mechanically activated W-Cu powders

Mechanically activated W-Cu powders were sintered by a spark plasma sinteringsystem (SPS) in order to develop a new process and improve the properties of the alloy. Propertiessuch as density and hardness were measured. The microstructures of the sintered W-Cu alloy sampleswere observed by SEM (scanning electron microscope). The results show that spark plasma sinteringcan obviously lower the sintering temperature and increase the density of the alloy. This processcan also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders withhigh density and superior physical properties.

Effect of closed-couple gas atomization pressure on the performances of Al-20Sn-1Cu powders

Al-20Sn-1Cu powders were prepared by gas atomization in an argon atmosphere with atomizing pressures of 1.1 and 1.6 MPa. The characteristics of the powders are determined by means of dry sieving, scanning electron microscopy （SEM）, optical microscopy （OM）, and X-ray diffractometry （XRD）. The results show that the powders exhibit a bimodal size distribution and a higher gas pressure results in a broad size distribution. All particles in both cases are spherical or nearly spherical and satellites form on the surface of coarse particles. Dendritic and cellular structures coexist in the particle. With decreasing particle diameter, the secondary dendrite arm spacing （SDAS） decreases and the cooling rate increases. The particles processed under high gas atomization pressure （1.6 MPa） exhibit a lower SDAS value and a higher cooling rate than those of the same size under low gas atomization pressure （1.1 MPa）. The XRD results show that the Sn content increases with decreasing particle size.

Fe含量对粉末冶金Cu-Fe合金显微组织与性能的影响

研究Fe含量对粉末冶金Cu-Fe合金显微组织及性能的影响。采用电火花等离子烧结、冷轧以及时效处理工艺制备4种不同铁含量(5%、10%、20%和40%,质量分数)的Cu-Fe合金。研究结果表明,随着Fe含量从5%(质量分数)增加到40%(质量分数),Fe相由离散球形分布演变为连续交错分布,Fe相尺寸从0.29μm增加到1.20μm;时效态的Cu-Fe合金的屈服强度从411.5 MPa提高到788.8 MPa,电导率从62.5%(IACS)降低到42.0%(IACS)。在以上结果的基础上,提出一种混合法则计算Cu基体、初级Fe相和次级Fe相对屈服强度的贡献,可较好地预测Fe含量高于10%(质量分数)合金的力学性能。

Microstructures of Sintered Mo-Cu Alloys with Mechanically Activated Powder

Mechanical activation and liquid phase sintering were used to manufacture high performance Mo-Cu alloy and develop new processes. The microstructures and properties of the alloy were investigated. The experimental results showed that: (1) the ball milled Mo/Cu powder has lamellar structure, (2) the microstructures of the sintered Mo-Cu alloy were homogenous compound structures of adhesive phase Cu linking Mo grains, (3) Mo grains frequently strung or gathered in Cu phase, and (4) the full densities of Mo-Cu alloy was achieved through sintering and special densification process. As a result, the properties of the alloy are good enough to satisfy various requirements.

Microstructural evolution during direct laser sintering of multi-component Cu-based metal powder

A multi-component Cu-based metal powder was chosen for direct laser sintering. The powder consists of a mixture of high-purity Cu powder, pre-alloyed CuSn and CuP powder. Liquid phase sintering with complete melting of the binder (CuSn) but non-melting of the cores of structural metal (Cu) proves to be a feasible mechanism for laser sintering of this powder system. The microstructural evolution of the sintered powder with variation of laser processing parameters was presented. High sintering activities and sound densification response were obtained by optimizing the laser powers and scan speeds. Using a high laser power accompanied by a high scan speed gives rise to balling effect. At a high laser power with a slow scan speed the sintering mechanism may change into complete melting/solidification, which decreases the obtainable sintered density. The role of additive phosphorus in the laser sintering process is addressed. Phosphorus can act as a fluxing agent and has a preferential reaction with oxygen to form phosphatic slag, protecting the Cu particles from oxidation. The phosphatic slag shows a concentration along grain boundaries due to its light mass as well as the short thermal cycle of SLS.

纳米W-Cu复合粉体制备的研究进展

W-Cu复合材料结合了W、Cu金属各自优良性能,具有良好的高温强度、延展性、抗电弧烧结性、耐高温氧化和低膨胀系数等特点,广泛应用于机械加工、国防工业、航空航天、电子信息、军事等领域。以超细纳米W-Cu复合粉体为原材料是制备出性能优越的W-Cu复合材料的主要途径之一,受到国内外学者的广泛关注。主要总结了W-Cu超细纳米复合粉体的制备方法,如机械合金化法、化学共沉淀法、水热合成-共还原法、喷雾干燥法、溶胶-凝胶法、冷冻-干燥法、燃烧法等,并通过分析现阶段制备W-Cu纳米复合粉体存在的问题,提出了未来该领域的研究方向。

Microstructure and Properties of W-Cu Alloys Prepared with Mechanically Activated Powder

W-15% Cu (mass fraction) alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of alloys. The microstructures of the activated powder and the sintered alloy were observed. Properties such as density were measured. The results show that through mechanical activation, the particle size of the powder becomes finer to sub-micron or nanometer level, some copper was soluble in tungsten, and high density W-Cu alloys can be obtained by mechanically activated powder for its action to the activation sintering.

Preparation of nanosized W/Cu composite powder by sol-gel technique

Cu(NO3)(2) and (NH4)(6)H(2)W(12)O(40)center dot 4H(2)O were used to prepare W/Cu nanosized composite powder by sol-gel technique. The influences of heat treatment process, pH value of the solution and the amount of an addition agent on particle size were investigated by DSC, XRD and TEM. The results show that, at a certain heat treatment temperature, the W/Cu nanoparticle size increases with the pH value or the amount of the addition agent increasing.

Fabrication of W@Cu Composite Powders by Direct Electroless Plating Using a Dripping Method

A direct electroless copper （Cu） coating on tungsten powders method requiring no surface treatment or stabilizing agent and using glyoxylic acid （C2H203） as a reducing agent was reported. The effects of copper sulfate concentration and the pH of the plating solution on the properties of the prepared W@Cu composite powders were assessed. The content of Cu in the composite powders was controlled by adjusting the concentration of copper sulfate in the electroless plating solution. A uniform, dense, and consistent Cu coating was obtained under the established optimum conditions （flow rate of C2H203 = 5.01 mL/min, solution pH = 12.25 and reaction temperature 45.35℃） by using central composite design method. In addition, the crystalline Cu coating was evenly dispersed within the W@Cu composite powders and Cu element in the coating existed as Cu~. The formation mechanism for the W@Cu composite powders by electroless plating in the absence of surface treatment and stabilizing agent was also proposed.

Synthesis and characterization of carbon nanotubes reinforced AI-Si-Cu brazing powder

In this paper, an approach to synthesizing carbon nanotubes （ CNTs ） reinforced A1-Si-Cu brazing powder was studied, which was accomplished by in-situ growth of the CNTs on the Al-Si-Cu powder at a relatively low temperature by plasma enhanced chemical vapor deposition （ PECVD ）. The synthesis parameters were optimized. The component of brazing powder was analyzed by X-ray diffraction （ XRD ）. The microstracture and dispersity of as-grown CNTs were investigated by scanning electron microscopy （SEM）. The graphitization and defects were characterized by Raman spectroscopy. The asgrown CNTs on Al-Si-Cu powder disperse uniformly and have moderate length and density, meanwhile its sp2 structure dominates minor quantity of amorphous carbons and defected carbon structures.

Preparation for intermetallic powders of Cu-Sn and Cu-Ni-Sn systems via solid-liquid reaction milling technique

The Cu-Sn binary intermetallic powders were obtained via a patented reaction ball milling technique. The Sn melt reacted with the solid-state Cu during the milling process at different temperatures for different intervals. Two kinds of binary intermetallics were obtained. For 12 h,Cu6Sn5 was prepared by milling Sn melt at 573 K while Cu3Sn by milling Sn melt at 773 K. And a mixture of Cu6Sn5 and Cu3Sn was fabricated at 673 K. All these intermetallic powders had mean grain sizes of less than 100 nm. A finer microstructure was obtained by milling Sn melt blended with 20%(mass fraction) Ni powders at 573 K for 12 h. The reaction mechanism and advantages were discussed in comparison with that of high-energy ball milling. The results show the solutionizing of Ni powders in the Cu6Sn5 intermetallic.

Relationship between powder characteristic and internal oxidation of Al in Cu-Al pre-alloyed powders

Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al2O3 composite, the apparent activation energy of Al internal oxidation reaction in Cu-Al pre-alloyed powders with different characteristics was calculated in the present investigation. The microstructure and properties of the synthesized Cu/Al2O3 were studied. The results show that high-energy milling can obviously promote internal oxidation of Al in Cu-Al powders in the same solid solubility. At the same milling conditions and internal oxidation parameters, the solid solution of Al in Cu either in low or high amount will result in the poor microstructure and properties of the Cu/Al2O3 composite. Subsequently, when high-energy milling and internal oxidation are synchronously used to prepare the Cu/Al2O3 composite, there should be an appropriate solubility and milling effect for the pre-alloyed powders.

球墨铸铁表面激光熔覆NiCu合金的扫描路径规划

采用同轴送粉激光熔覆技术,在球墨铸铁节点套样件上制备Ni-Cu合金熔覆层对球墨铸铁节点套进行修复。在相同工艺参数的基础上,依据节点套结构特点设计了样件宽度方向A、B对半分区搭接、沿圆周单向熔覆轴向搭接和轴向往返熔覆“弓”字形搭接3种不同扫描路径。对3种不同扫描路径下激光熔覆样件的宏观形貌特征、服役界面的渗透探伤无损检测结果及金相组织、显微硬度的对比分析发现,采用沿圆周单向熔覆轴向搭接的方式得到的样件表面熔覆层无缺陷,质量佳。

粉末锻造Al_(2)O_(3)颗粒增强Fe–Ni–Mo–C–Cu复合材料的组织与性能

通过粉末锻造技术制备了不同含量微米级Al_(2)O_(3)颗粒强化的Fe–Ni–Mo–C–Cu(Q61)复合材料,并对调质态和淬火态复合材料的组织和性能进行了研究。结果表明:当Al_(2)O_(3)质量分数为0.15%时,增强颗粒在基体内分布均匀;相较于同种状态下不添加增强颗粒的单一Q61,调质态复合材料的硬度从HRC 38增至HRC 39.8,屈服强度从1106 MPa增至1121 MPa,延伸率从12%降至6.5%;淬火态复合材料的硬度从HRC 61.5增至HRC 63.2,磨损率从5.27×10^(-6)mm^(3)·m^(-1)·N^(-1)降至3.08×10^(-6)mm^(3)·m^(-1)·N^(-1),低于对比试验用的典型齿轮材料40Cr的磨损率(3.34×10^(-6)mm^(3)·m^(-1)·N^(-1))。当Al_(2)O_(3)质量分数大于0.15%时,Al_(2)O_(3)颗粒逐渐偏聚,虽然调质态下复合材料屈服强度仍继续小幅增加,但塑性严重退化,且淬火态复合材料磨损率增加,耐磨性变差。综合来看,添加0.15%Al_(2)O_(3)颗粒强化Q61复合材料在调质态下具有较高的综合力学性能,而在淬火态下表现出良好的抗摩擦磨损能力。

Development of Cu-Exfoliated Graphite Nanoplatelets (xGnP) Metal Matrix Composite by Powder Metallurgy Route

In the present investigation the possibility of using exfoliated graphite nanoplatelets (xGnP) as reinforcement in order to enhance the mechanical properties of Cu-based metal matrix composites is explored. Cu-based metal matrix composites reinforced with different amounts of xGnP were fabricated by powder metallurgy route. The microstructure, sliding wear behaviour and mechanical properties of the Cu-xGnP composites were investigated. xGnP has been synthesized from the graphite intercalation compounds (GIC) through rapid evaporation of the intercalant at an elevated temperature. The thermally exfoliated graphite was later sonicated for a period of 5 h in acetone in order to achieve further exfoliation. The xGnP synthesized was characterized using SEM, HRTEM, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The Cu and xGnP powder mixtures were consolidated under a load of 565 MPa followed by sintering at 850°C for 2 h in inert atmosphere. Cu-1, 2, 3 and 5 wt% xGnP composites were developed. Results of the wear test show that there is a significant improvement in the wear resistance of the composites up to addition of 2 wt% of xGnP. Hardness, tensile strength and strain at failure of the various Cu-xGnP composites also show improvement upto the addition of 2 wt% xGnP beyond which there is a decrease in these properties. The density of the composites decreases with the addition of higher wt% of xGnP although addition of higher wt% of xGnP leads to higher sinterability and densification of the composites, resulting in higher relative density values. The nature of fracture in the pure Cu as well as the various Cu-xGnP composites was found to be ductile. Nanoplatelets of graphite were found firmly embedded in the Cu matrix in case of Cu-xGnP composites containing low wt% of xGnP.

Cu含量对多孔Ti-5Mn合金微观结构及力学性能的影响

以质量分数为50%的碳酸氢铵颗粒为造孔剂,使用粉末冶金工艺经真空烧结制备出多孔Ti-5Mn-xCu(x=0,3,5,10)合金,并研究了Cu含量对多孔Ti-5Mn合金微观结构及力学性能的影响。研究结果显示,制备得到的多孔Ti-Mn-Cu合金的孔隙率随着Cu含量的增加而逐渐降低,其大孔孔径略为减小,大孔壁上微孔数量逐渐减少。多孔Ti-Mn-Cu合金中出现了Ti_(2)Cu相,并且其相对含量随着Cu含量的增加逐渐增多。多孔Ti-Mn-Cu合金的弹性模量和抗压强度均随Cu含量的增加而提高。含3%~10%Cu和5%Mn的多孔Ti-Mn-Cu合金具有合适的孔结构和与人体骨相近的力学性能,具有作为抗菌骨科植入材料的潜力。

纳米W-Cu粉末的均相沉淀法制备及其烧结性能

采用湿化学工艺———蒸氨均相沉淀法, 制备了纳米 CuWO4 ·2H2O/Cu2WO4 (OH)2 均相沉淀物, 然后煅烧、还原, 得到含Cu 30%的W Cu复合粉。将该复合粉压坯在H2 气氛中于不同温度下烧结后, 对烧结体的微结构和物理、力学性能等进行了测试分析。实验结果表明: 蒸氨均相沉淀法制备的 W Cu复合粉体具有纳米粒度和均匀的化学组成, 其烧结活性高, 在较低温度下烧结即可达很高的致密化程度。由上述 W Cu粉体所制备的烧结体具有良好的物理、力学性能。

纳米Cu粉对HMX和RDX热分解的催化作用

采用DSC、PDSC、TG-DTG探讨了纳米金属Cu粉对HMX、RDX热分解的催化作用。结果表明,纳米Cu粉对HMX的固相分解和RDX液相分解的加速作用明显。随着纳米金属Cu粉含量的增加,HMX的固相分解逐渐提前,当HMX与纳米Cu粉的质量比为11时,HMX固相分解的开始温度提前25.5℃;常压下纳米金属Cu粉使RDX的液相分解的分解峰温从239.1℃提前到220.9℃。Cu粉的稀释和分散(或散热)作用使放热焓下降。

直流氢电弧蒸发法制备金属纳米Ni粉和Cu粉的研究

采用自行设计的直流氢电弧等离子体蒸发设备,通过正交试验,系统研究了H2/Ar、电流和压力对纳米Ni粉和Cu粉制备产率、结构及粒度的影响。发现:(1)该设备能够制备出纳米级的Ni粉和Cu粉,且产率有了很大的提高,Ni粉最大产率提高了24倍,Cu粉的最大产率提高了203.7倍;(2)各因素对两种粉体制备产率影响的显著性顺序为:φ(H2)/φ(Ar)-电流-压力;对Ni粉平均粒径影响的显著性顺序为:φ(H2)/φ(Ar)-压力-电流;对Cu粉平均粒径影响的显著性顺序则为:压力-φ(H2)/φ(Ar)-电流;(3)所制备的纳米Ni粉和Cu粉为多晶型;Ni粉的平均粒径在20～65nm范围内;Cu粉平均粒径为23～141nm;制备的Ni粉中不含杂质,纯净度很高,但是Cu粉中含有一定量的CuO杂质;(4)设备内腔的冷却环境对控制极大粒度粉体的生成和粉体粒度分布具有重要影响。

自悬浮定向流法制备纳米Cu粉的微结构和性能表征

采用自悬浮定向流法制备纳米Cu粉;用透射电镜、X射线衍射、紫外-可见光吸收光谱、差示扫描量热-热重法和X射线光电子能谱分析对纳米Cu微晶的形貌、粒度、结构和性能进行研究。研究结果表明:在体积分数为10%He和90%Ar混合气流中和在Ar气流中制备的纳米Cu粒子形貌呈球形,平均粒度分别约为45和60 nm;在590 nm左右有1个很强的吸收峰;纳米Cu粒子表面Cu和O元素的摩尔比为94.88:5.12,有少量氧化亚铜和氧化铜的混合物存在,但在其表面未发现Ar和N。