Al含量对ONTs/镁基复合材料显微组织和力学性能的影响

研究了Al含量时CNTs/镁基复合材料显微组织和力学性能的影响.结果表明:Al是CNTs/镁基复合材料中强化相β相的组成元素,Al含量的增加使CNTs/镁基复合材料中β相也增加,提高了复合材料的强度但降低了其塑性.当Al含量为8%时,复合材料晶粒细小,并具有最佳的强度、硬度和塑性组合;随着Al含量的进一步增加,β-Mg17Al12相析出增加,在复合材料中出现粗大的、沿晶界连续分布的金属间化合物Mg17Al12相,导致抗拉强度和伸长率下降.     

Al含量对CNTs／镁基复合材料显微组织和力学性能的影响

研究了Al含量对CNTs／镁基复合材料显微组织和力学性能的影响。结果表明：Al是CNTs／镁基复合材料中强化相p相的组成元素,Al含量的增加使CNTs／镁基复合材料中β相也增加,提高了复合材料的强度但降低了其塑性。当Al含量为8％时,复合材料晶粒细小,并具有最佳的强度、硬度和塑性组合;随着Al含量的进一步增加,β-Mg17Al12相析出增加,在复合材料中出现粗大的、沿晶界连续分布的金属间化合物Mg17Al12相,导致抗拉强度和伸长率下降。     

CNTs对TC4与C/C复合材料钎焊接头组织及力学性能的影响

试验采用加入了碳纳米管(carbon nanotubes,CNTs)的AgCu4.5Ti + xCNTs (x为质量分数,%)复合钎料(简称AgCuTi_C复合钎料),实现了TC4钛合金与C/C复合材料的真空钎焊连接. 通过SEM,EDS等分析手段确定了在CNTs含量为0.2%、钎焊温度为880 ℃、保温时间为20 min时接头的典型界面组织为TC4/扩散层/Ti₂Cu/TiCu/Ti₃Cu₄/TiCu₄/TiC + TiCu₂ + Ag(s.s) + Cu(s.s)/Ti₃Cu₄/TiCu₄/TiC/C/C复合材料;研究了CNTs含量对接头组织与性能的影响. 结果表明,随着CNTs含量的增加,钎缝宽度变化呈下降趋势,界面组织细化,界面中的Ti₃Cu₄与TiCu₄脆性化合物的含量降低、TiC与TiCu₂化合物的含量增加;接头的抗剪强度呈先上升后下降的趋势变化;当CNTs含量为0.4%时抗剪强度最高,达到44 MPa;CNTs的加入可使界面组织得到细化,有利于缓解钎缝中心区域与两侧母材之间存在的由于热膨胀系数不匹配而形成的较大残余应力,有效地提高了接头的抗剪强度.     

碳纳米管增强Cu和Al基复合材料的研究进展

碳纳米管(CNTs)增强Cu基或Al基复合材料是未来铜材或铝材方面最具潜力的发展方向之一。在本研究中,综述了近几年在CNTs增强Cu基和Al基复合材料研究方面取得的进展,论述CNTs的预处理、CNTs-金属复合粉末的制备、CNTs-金属复合块体材料的制备、界面结合机制以及CNTs的强化机理5个主要方面。     

Cu-Al金属间化合物的形成与生长及其对电镀Cu/Al层状复合材料电性能的影响（英文）

采用纯Al片表面浸Zn后再电镀厚Cu层的方法制备Cu/Al层状复合材料。在473~673 K温度范围内对该复合材料进行退火,研究退火过程中Cu/Al界面扩散与反应、界面金属间化合物(IMCs)层的长大动力学以及Cu/Al层状复合材料电阻率。结果表明,经过473 K、360 h的退火处理,未观察到Cu-Al IMCs层,显示Zn中间层能有效抑制Cu/Al界面扩散。可是,当复合材料经573 K及以上温度退火时,Zn层中的Zn原子主要向Cu中扩散,从Al侧到Cu侧形成CuAl_2/CuAl/Cu_9Al_4三层结构的反应产物。IMC层遵循扩散控制的生长动力学,Cu/Al复合材料的电阻率随退火温度及时间的增加而增大。     

Yb对2519A铝合金抗剥落腐蚀性能的影响

采用铸锭冶金法制备了不同Yb含量的2519A铝合金试样,通过硬度测试、力学性能测试、金相显微镜、扫描电镜与透射电镜等分析方法研究了稀土Yb对2519A铝合金抗剥落腐蚀性能的影响。结果表明:在2519A铝合金中添加0.2%Yb(质量分数)时,Yb与Al,Cu,Fe和Mn形成稀土相,合金内粗大Al Cu相和Al Cu Fe Mn相数量减少,含Yb第二相粒子化学活泼性低于Al Cu相和Al Cu Fe Mn相。适量的Yb能细化合金的时效强化相,使其析出密度增加,阻止θ(Al2Cu)相在晶界上连续析出,减小晶界无沉淀析出带(PFZ)宽度,使晶界析出相变成非连续分布,从而改善了合金的剥落腐蚀抗力。当Yb含量进一步增加时,合金力学性能及抗剥蚀性能下降。     

热处理过程中SiCp/2024Al基复合材料的微观组织演变

采用真空热压烧结工艺在580℃下制备了35%(体积分数)SiCp/2024铝基复合材料,利用扫描电镜(SEM)、透射电镜(TEM)、能谱(EDS)、高分辨透射电镜(HRTEM)对复合材料热处理过程中微观组织进行了表征,研究了热压烧结后复合材料的析出相的微观结构以及析出相在热处理过程的演变规律。结果表明,热压烧结后复合材料中存在许多粗大析出相颗粒,包括Al4Cu9,Al2Cu,Al18Mg3Mn2,Al5Cu6Mg2和Al7Cu2Fe。随着固溶温度的提高,粗大析出相颗粒逐渐回溶到Al基体中,当固溶温度达到510℃时,粗大析出相颗粒几乎全部回溶到基体中,但还存在少量的难溶相。复合材料经510℃固溶2 h+190℃时效9 h后,除了少量的难溶相,许多圆盘状纳米析出相Al2Cu和棒针状纳米析出相Al2Cu Mg弥散分布于基体中且与基体的界面为错配度较小的半共格界面,圆盘状纳米析出相的直径为50~200 nm,棒针状纳米析出相长度为100~150 nm。     

Al2O3晶须与石墨烯纳米片共增强铜基复合材料的显微结构及界面行为(英文)

研究Al₂O₃晶须和石墨烯纳米片共增强铜基复合材料的力学性能和显微结构。采用机械合金化、真空热压烧结和热等静压工艺制备不同石墨烯含量的铜基复合材料。含0.5%石墨烯(质量分数)的铜基复合材料(GNP-0.5)具有良好的Cu/C和Cu/Al₂O₃界面结合性能;复合材料的硬度和抗压强度随石墨烯含量的增加呈现先增加到一个临界值后减小的趋势。研究结果表明,石墨烯和Al₂O₃晶须在铜基复合材料中最主要的强化机制是能量耗散和载荷传递以及石墨烯导致的晶粒细化。石墨烯与Al₂O₃晶须的双相混杂增强效应在于：当Al₂O₃/Cu界面存在微裂纹并沿着界面扩展时,嵌于铜基复合材料中的石墨烯会阻碍裂纹扩展路径,从而强化Al₂O₃晶须在铜基复合材料中的增强作用。     

碳纳米管增强铜基复合材料的制备、力学性能及电导率

以CNTs、电解Cu粉、Cu(CH_3COO)_2·H_2O为原料,采用混酸处理、分子水平法结合行星球磨两步混合工艺制备含0.5%～2%(质量分数)CNTs的Cu基复合粉末,然后通过放电等离子烧结技术制备了Cu-CNTs复合材料,探讨了制备工艺及CNTs含量对Cu-CNTs复合材料的组织、电导率和力学性能的影响规律。结果表明:当CNTs含量小于1.0%时,采用两步混粉工艺制备的Cu-CNTs复合粉体均匀性、分散性良好,经烧结后可获得致密度高、CNTs分布均匀的Cu-CNTs复合材料;当CNTs含量大于1.0%时,复合材料的致密度及CNTs分布均匀性明显降低;随CNTs含量的提高,复合材料的强度先升高后降低,塑性和电导率趋于降低;相对高能球磨、分子水平法等单一混粉工艺而言,两步法制备的Cu-1.0%CNTs复合材料综合性能更优,其电导率为51.7 MS/m(89.1%IACS),维氏硬度为1130 MPa,抗拉强度为279 MPa,断后伸长率为9.8%。     

Ni-P镀层对Cu/Al钎焊界面结构及性能的影响机制

为了研究Ni-P镀层对Cu/Al异种金属钎焊界面反应的影响,首次采用Zn98Al和BAl67CuSi两种钎料对含/不含Ni-P镀层的T2紫铜与3003铝合金进行了高频钎焊,获得4种不同的钎焊接头,分别对接头Cu侧界面结构、抗剪强度、断口形貌、显微硬度及弯曲形貌进行了系统研究,并与无镀层接头进行对比. 结果表明,T2表面镀覆Ni-P后,Cu/Zn98Al/Al接头中Cu基体/钎缝界面结构由扩散层+8.8 μm厚的Cu_3.2Zn_4.2Al_0.7化合物转变为1.5 μm厚的Al₃Ni化合物,而Cu/BAl67CuSi/Al接头中Cu基体/钎缝界面结构由扩散层+15 μm厚CuAl₂转变为1.8 μm厚Cu₃NiAl₆;与无镀层接头相比,镀覆Ni-P后,Cu/Zn98Al/Al接头强度略有上升,Cu/BAl67CuSi/Al接头强度略有下降,但两种接头的韧性均明显增强,力学性能试验结果与接头Cu侧界面微观组织转变规律相符. 最后建立了Cu/Al接头的界面反应模型,并阐明了Ni-P镀层对Cu/Al接头界面结构和力学性能的影响机制.     

Effect of Spark-Plasma-Sintering Conditions on Tensile Properties of Aluminum Matrix Composites Reinforced with Multiwalled Carbon Nanotubes (MWCNTs)

In this study, aluminum (Al) matrix composites containing 2 wt.% multiwalled carbon nanotubes (CNTs) were fabricated by powder metallurgy using high-energy ball milling (HEBM), spark plasma sintering (SPS), and subsequent hot extrusion. The effect of SPS conditions on the tensile properties of CNT/Al composites was investigated. The results showed that composites with well-dispersed CNTs and nearly full-density CNT/Al can be obtained. During HEBM, CNTs were shortened, inserted into welded Al powder particles, bonded to Al, and still stable without CNT-Al reaction. After consolidation, Al₄C₃ phases formed in composites under different sintering conditions. With the increase of sintering temperature and holding time, the strength decreased. Conversely, the ductility and toughness noticeably increased. As a result, a good balance between strength (367 MPa in ultimate tensile strength) and ductility (13% in elongation) was achieved in the as-extruded CNT/Al composite sintered at 630°C with a holding time of 300 min.     

Ti 元素对B4C/Al复合材料力学性能的改善作用研究

B₄C/Al复合材料是目前最理想的中子吸收材料,广泛用于乏燃料储存。本文利用液态搅拌法制备B₄C/Al复合材料,通过添加Ti元素,探讨了界面反应对材料的界面结构和力学性能的影响。研究发现,Ti元素通过参与界面反应,改变了界面结构,在B₄C颗粒表面形成了紧密结合的纳米TiB₂界面层;Ti的添加消除了界面微裂纹、微孔、分离等缺陷。随着界面反应程度的加强,材料强度提高,尤其反应脱落的纳米TiB₂颗粒作为原位第二强化相进一步增强基体。B₄C/Al复合材料断裂过程表现为韧窝延性断裂;TiB₂界面层增强了B₄C颗粒与基体的结合,断裂行为从B₄C-Al界面脱落转变为B₄C颗粒断裂;但过渡的界面反应会形成微韧窝,引起材料延伸率下降。     

Effect of limited matrix–reinforcement interfacial reaction on enhancing the mechanical properties of aluminium–silicon carbide composites

An unconventional approach to strengthening Al/SiC composites through controlled matrix–reinforcement interfacial reactions was studied. Composites with two distinct interfacial microstructures were prepared by varying the contact time between the SiC particles and molten aluminium during processing. The formation of a thin Al₄C₃ reaction layer along the particle–matrix interface was found to increase the composite yield strength, ultimate tensile strength, work-hardening rate and work-to-fracture, and change the fracture pattern from one involving interfacial decohesion to one where particle breakage was dominant. These changes were attributed to a stronger interface bond, which is thought to result from the tendency for the Al₄C₃ reaction layer to form semicoherent interfaces and orientation relationships with the aluminium matrix and SiC particles and for it to be mechanically “keyed-in” to both these phases. The stronger interface bond also enhanced the levels of plastic constraint which, when coupled with the greater work hardening, promoted local matrix failure, thereby reducing the composite ductility.     

Fabrication of carbon nanotube reinforced AZ91D composite with superior mechanical properties

AZ91D alloy composites with 1.0% CNTs have been fabricated by a method combined ball milling with stirring casting. The composite was investigated using optical microscopy(OM), X-ray diffraction(XRD), Fourier transform infrared spectroscope (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and room temperature (RT) tensile test. The results show that CNTs were homogeneously distributed in the matrix and maintained integrated structure. The yield strength and ductility of AZ91D/CNTs composite were improved by 47.2% and 112.2%, respectively, when compared with the AZ91 alloy. The uniform distribution of CNTs and the strong interfacial bonds between CNT and the matrix are dominated to the simultaneous improvement of yield strength and ductility of the composite. In addition, the grain refinement as well as the finer β phase (Mg₁₇Al₁₂) with homogenous distribution in the matrix can also slightly assist to the enhancement of the mechanical properties of the composite.     

Superplastic behavior of PM SiCp/6061 aluminum alloy composites at high strain rates

The superplastic behavior of a powder-metallurgy processed 6061 Al composite was investigated as a function of SiC content increasing from 0% to 30% at 10% increments over a wide temperature range from 430°C to 610°C. The materials were found to be high-strain-rate superplastic. In the temperature range where grain boundary sliding (GBS) controlled the plastic flow, the strength of the composite was lower than that of the unreinforced matrix alloy even after compensating for grain size and threshold stress. This “particle weakening” was in contrast with the particle strengthening observed in the low temperature range where dislocation climb creep was found to control the plastic flow. In the GBS regime, the strength differential between the materials was a function of SiC content and temperature, which increased with the increase in SiC content and temperature. Strong Mg segregation was detected at interfaces between SiC and Al phases in the composites. Evidence for interfacial reaction reported in the Si₃N₄ reinforced 6061 Al composites could not be detected in the current composites. Extensive formation of whisker-like fibers was observed at the fractured surface of the tensile samples above the critical temperature where particle weakening begins to be exhibited. This result suggests the possibility that partial melting in the solute-enriched region near SiC interfaces is responsible for the particle weakening in the SiC reinforced 6061 Al composite.     

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiC_p particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiC_p/Al composites. Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing, hot extrusion and heat treatment. The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti₅Si₃ phases at the interface. Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles. The microstructure, relative density and mechanical properties of the composite are significantly improved. When the volume fraction is 15%, the hardness, fracture strain and tensile strength of the SiC_p reinforced Al 2519 composite after Ti plating are optimized, which are HB 138.5, 4.02% and 455 MPa, respectively.     

Interfacial reaction in ASZ/A384 Al composite and its influence on mechanical properties

In an ASZ/A384 Al composite, the interfacial reaction was observed to take place between the SiO₂ binder layer and Mg within the matrix to form MgAl₂O₄ at the interface. Formation of MgAl₂O₄ at the interface between ASZ short fibers and the Al matrix alloy is believed to enhance the interfacial bonding strength, resulting in improved composite strength. However, the interfacial reaction in the ASZ/A384 Al proceeds at the expense of Mg in the matrix, resulting in a composite devoid of Mg bearing precipitates such as Al₂CuMg and Mg₂Si.     

混杂增强(CNTs+TiB2)/Cu复合材料制备与性能

本文以碳纳米管（CNTs）和TiB2颗粒作为增强相,首先利用球磨、表面吸附和热压烧结相结合技术制备具有层叠结构的CNTs/Cu复合材料,改善了CNTs在铜基复合材料中易团聚问题。CNTs/Cu复合材料的致密度和导电率随CNTs含量增加而降低,抗拉强度和伸长率随CNTs含量增加先升高后降低,当含量为0.1 wt.%时综合性能最优,致密度、导电率和抗拉强度分别为97.57%、91.2 %IACS和252 MPa。而球磨后热压烧结的1 wt.% TiB2/Cu复合材料致密度、导电率和抗拉强度分别为97.61%、58.3 %IACS和436 MPa。在此基础上,将TiB2颗粒原位引入到具有层叠结构的CNTs/Cu复合材料,制备获得混杂增强(CNTs+TiB2)/Cu复合材料。相比单一CNTs（或TiB2）增强铜基复合材料,(CNTs+TiB2)/Cu复合材料的强度提升显著。其中,(0.1 wt.% CNTs+1 wt.% TiB2)/Cu复合材料的导电率和抗拉强度分别为56.4 %IACS和531 MPa,相比1 wt.% TiB2/Cu,其导电率仅降低3.3%,而抗拉强度则升高21.8%。这主要归因于片层间CNTs可起承担和传递载荷作用,同时片层间弥散分布的TiB2颗粒可以钉扎位错,两种强化机制共同作用使(CNTs+TiB2)/Cu复合材料的抗拉强度显著提升。     

In situ formation of various intermetallic particles in Al–Ti–X(Cu,Mg) systems during friction stir processing

In situ Al composites reinforced by various intermetallic particles were fabricated from Al–Ti–X(Cu, Mg) systems by hot pressing, forging and subsequent 4-pass friction stir processing (FSP). The formation of various intermetallic particles during FSP and the tensile properties of in situ composites were investigated. For Al–Ti–Cu system, Cu enhanced the Al–Ti reaction and resulted in the formation of more Al₃Ti particles due to the presence of a small amount of liquid phase during FSP. After FSP, part of Cu was kept in the Al matrix as solute, whereas the other formed Al₂Cu particles. For Al–Ti–Mg system, except for Al₃Ti, some Ti₂Mg₃Al₁₈ particles with fine twin lamellas were formed during FSP, resulting in an increase in the total volume fraction of reinforcing particles. Cu and Mg addition increased the strength of the in situ composites substantially due to introduction of more strengthening modes and more reinforcing particles, however the elongation decreased dramatically.