Features of microstructure and fracture in the transient liquid phase bonded aluminium-based metal matrix composite joints

Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).

Transient liquid phase bonding of TiC particulate reinforced magnesium metal matrix composite (TiC_p/AZ91D)

Microstructures and mechanical properties of transient liquid phase （TLP） bonded magnesium metal matrix composite （ MMC） joints using copper interlayer have been investigated. With an increase of bonding times from 5 min to 50 min at bonding temperature of 510 ℃ , the average concentration of copper in the bonded zone decreased, the microstructure in the zone changed from Cu, α-Mg and CuMg2 to α-Mg, CuMg2 and TiC, and mechanical properties of the joint increased. The shear strength of the joint bonded at 510 ℃ for 50 min reached 64 MPa due to the metallurgical bonding of the joint and improving its homogeneity of composition and microstructure. It is favorable to increase the bonding time for improving mechanical properties of TLP bonded magnesium MMC joint.

Development of Al-12Si-xTi system active ternary filler metals for Al metal matrix composites

To improve the wettability of Al metal matrix composites（Al-MMCs） by common filler metals,Al-12Si-xTi（x=0.1,0.5,1,3.0;mass fraction,%） system active ternary filler metals were prepared.It was demonstrated that although the added Ti existed within Ti（Al1-xSix）3（0≤x≤0.15） phase,the shear strength and shear fracture surface of the developed Al-12Si-xTi brazes were quite similar to those of traditional Al-12Si braze due to the presence of similar microstructure of Al-Si eutectic microstructure with large volume fraction.So,small Ti addition（～1%） did not make the active brazes brittle and hard compared with the conventional Al-12Si braze.The measured melting range of each Al-12Si-xTi foil was very similar,i.e.,580-590 ℃,because the composition was close to that of eutectic.For wettability improvement,with increasing Ti content,the interfacial gap between the Al2O3 reinforcement and filler metal（R/M） could be eliminated,and the amount of the remainder of the active fillers on the composite substrate decreased after sessile drop test at 610 ℃ for 30 min.So,the wettability improvement became easy to observe repeatedly with increasing Ti content.Additionally,the amount and size of Ti（AlSi）3 phase were sensitive to the Ti content（before brazing） and Si content（after brazing）.

Formation process, microstructure and mechanical property of transient liquid phase bonded aluminium-based metal matrix composite joint

The formation process, microstructure and mechanical properties of transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joint with copper interlayer were investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid diffusion (stage 1), dissolution of interlayer and base metal (stage 2), isothermal solidification (stage 3) and homogenization (stage 4). The microstructure of the joint depends on the joint formation process (distinct stages). The plastic deformation and solid diffusion in stage 1 favoure the intimate contact at interfaces and liquid layer formation. The microstructure of joint consists of aluminium solid solution, alumina particle, Al 2Cu and MgAl 2O 4 compounds in stage 2. The most pronounced feature of joint microstructure in stage 3 is the alumina particle segregation in the center of the joint. The increase of joint shear strength with increasing bonding temperature is mainly attributed to improving the fluidity and wettability of liquid phase and decreasing the amount of Al 2Cu brittle phase in the joint. The principal reason of higher bonding temperature (>600 ℃) resulting in lowering obviously the joint shear strength is the widening of alumina particle segregation region that acts as a preferential site for failure. The increase of joint shear strength with increasing holding time is mainly associated with decreasing the amount of Al 2Cu brittle phase and promoting homogenization of joint.

Development of three kinds of active ternary filler metals of AI-Si-Ti, Zn-AI-Ti and Cu-AI-Ti systems for AI metal matrix composites

To improve the wettability of common fiUer metals on Al metal matrix composites （ AI-MMCs ） , three kinds of active ternary filler metals, Al-Si-Ti, Zn-Al-Ti and Cu-Al-Ti systems, were prepared by the addition of Ti. Excessive melting temperature made the gravity segregation of Ti remarkable in ingot. The effect of Ti content on the melting point for AI-Si-Ti ternary system was not as sensitive as that for Al-Ti binary system. The Al-12Si-1Ti filler metal showed good ability to form brazing foil during rapid cooling, ductile fracture surface and similar shear strength to conventional Al-12Si filler metal. Moreover, the Al2 03 reinforcements on initial surface could be covered by the Al-12Si-1Ti filler metal without interfacial gaps after sessile drop test. For Zn-9.5Al-0. 5 Ti braze alloy, severe vaporization of Zn and severe segregation of Ti Occurred. During wettability test for traditional Al-12Si and Zn-9.5Al-0. 5Ti, although some Si or Zn could penetrate into the composite, interfacial gap still remained. The prepared Cu-19Al-1 Ti interlayer consisted of primary phase of Al4Cu9 and network Cu-Al-Ti ternary intermetaUic compound, showing poor ability to form foil and very brittle nature. These results demonstrated that Al-Si-Ti system should be promising for Al-MMCs.

Mg-Cu-Zn-Y-Zr bulk metallic glassy composite with high strength and plasticity

Mg65Cu20Zn5Y9Zr1 bulk metallic glass matrix composite with a diameter of 2 mm was produced by copper mold casting. Upon cooling the Mg65Cu20Zn5Y9Zr1 melt, Mg2Cu acicular crystalline phase precipitates uniformly with a size of about 20 μm long and 1 μm thick while the remaining melt undergoes glass transition. Room temperature compression tests revealed that the high fracture strength up to 830 MPa and the plastic strain of 2.4% before failure are obtained for the Mg-based bulk metallic glass matrix composite. The formation of the Mg2Cu phase was proposed to contribute to high strength and plastic deformation of the material.

MAX相陶瓷增强金属基复合材料:制备、性能与仿生设计

由于原子间存在共价键、金属键与离子键的混合键合状态,MAX相陶瓷兼具金属和陶瓷材料的性能特点,并且常与金属之间表现出良好的润湿性,有助于形成强界面结合,独特的层状原子结构使MAX相陶瓷表现出良好的断裂韧性、阻尼与自润滑性能。因此,作为金属基复合材料的增强相,MAX相陶瓷具有显著优势,本文着重介绍相关研究进展。目前,MAX相陶瓷增强金属基复合材料主要通过搅拌铸造、粉末冶金和熔体浸渗等途径制备,得到的复合材料表现出优于金属基体的强度、硬度与模量,同时还具备良好的耐磨、导电、抗电弧侵蚀等性能。此外,借助真空抽滤、冰模板等工艺可实现超细片状MAX相陶瓷粉体的择优定向排列,然后利用金属熔体浸渗多孔陶瓷骨架,可获得具有类贝壳结构的MAX相陶瓷增强金属基仿生复合材料,进一步提升材料的强韧性能。MAX相陶瓷增强金属基复合材料在承载、电接触等应用领域具有显著优势和广阔前景。

Effect of Cu content on microstructure and mechanical properties of in-situ β phases reinforced Ti/Zr-based bulk metallic glass matrix composite by selective laser melting(SLM)

In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu content on phase formation,microstructure,and mechanical properties is investigated.The average volume fraction and width of theβphase decreases with increasing Cu content,while a more amorphous phase and the(Ti,Zr)_(2)Cu phase forms.In the center zone of the molten pool,theβphase grows in the direction of the temperature gradient,and the amorphous phase distributes among theβphases.This occurs using:sphere morphology(for x=5),a more continuous elongated sphere and network morphology(for x=10),and network morphology(for x=15),respectively.In the edge zone of the molten pool,due to the smaller cooling rate and the existence of a partially molten zone,theβphase becomes coarser,and an amorphous phase forms for more continuous networks.Furthermore,the hardness improves significantly with increasing Cu content.No crack is found for x=5.Although the average volume fraction of theβphase for x=5 is about 90%,the compression yield strength is 1386±64 MPa,reaching to an average level of conventionally fabricated counterparts,due to finer microstructure,and twinning and martensitic transformation of theβphase.

Thermal Analysis of Metal Foam Matrix Composite Phase Change Material

In this paper,CPCM(Composite Phase Change Material)was manufactured with metal foam matrix used as filling material.The temperature curves were obtained by experiment.The performance of heat transfer was analyzed.The experimental results show that metal foam matrix can improve temperature uniformity in phase change thermal storage material and enhance heat conduction ability.The thermal performance of CPCM is significantly improved.The efficiency of temperature control can be obviously improved by adding metal foam in phase change material.CPCM is in solid-liquid two-phase region when temperature is close to phase change point of paraffin.An approximate plateau appears.The plateau can be considered as the temperature control zone of CPCM.Heat can be transferred fiom hot source and be uniformly spread in thermal storage material by using metal foam matrix since thermal storage material has the advantage of strong heat storage capacity and disadvantage of poor heat conduction ability.Natural convection promotes the melting of solid-liquid phase change material.Good thermal conductivity of foam metal accelerates heat conduction of solid-liquid phase change material.The interior temperature difference decreases and the whole temperature becomes more uniform.For the same porosity with a metal foam,melting time of solid-liquid phase change material decreases.Heat conduction is enhanced and natural convection is suppressed when pore size of metal foam is smaller.The thermal storage time decreases and heat absorption rate increases when the pore size of metal foam reduces.The research results can be used to guide fabricating the CPCM.

MAX/金属基自润滑复合材料的研究现状及进展

随着我国工业化进程推进,各领域对于固体润滑材料的要求不断提高,作为新一代固体自润滑材料的MAX/金属基固体自润滑复合材料因其优异的高温稳定性和良好的自润滑性能,受到了广泛的关注。文章就MAX/金属基固体自润滑复合材料的研究进程进行了总结,并综述了国内外研究者们在MAX/金属基固体自润滑复合材料方面所取得的进展,包括MAX性能和结构特征、MAX与石墨/金属基固体自润滑复合材料性能对比、MAX/金属基固体自润滑复合材料界面反应和润滑机理。最后,对MAX/金属基固体自润滑复合材料研究方向进行了进一步展望。

原位自生MAX相增强TiAl基复合材料

叙述了近年来国内外原位自生MAX相增强TiAl基复合材料的研究进展。叙述了MAX相结构和性能,MAX相增强TiAl基复合材料的原位合成工艺的研究进展及原位合成机理,并对复合材料的微观组织、界面结构以及力学性能进行了综述,最后对其应用进行展望。

多功能一体化MAX相改性连续纤维增韧陶瓷基复合材料的研究进展

连续纤维增韧陶瓷基复合材料(Ceramic Matrix Composites,CMCs)因其优异的性能在航空发动机、空天飞行器热防护系统、核能电站等领域具有广泛的应用前景。现阶段,CMCs的应用已由单一结构承载向多功能一体化发展。MAX相是一类能够发生塑性变形的三元层状陶瓷,具有高导电、抗辐照和抗烧蚀等优异性能,将其引入CMCs可实现强韧化与抗辐照/抗烧蚀/电磁屏蔽效能的协同提高,满足多功能一体化CMCs的应用需求。本文综述了MAX相作为CMCs界面相和基体相的研究进展,阐述了其设计机理,并展望了MAX相在CMCs中的应用前景。

MAX/金属基自润滑复合材料摩擦学研究

金属基自润滑复合材料因具有优良的力学性能及自润滑性能而受到广泛的关注.首先,介绍MAX相的结构、性能以及MAX相固体润滑剂的应用背景和优势.综述国内外金属基自润滑复合材料的研究进展.然后,讨论MAX/金属基自润滑复合材料的润滑机理并建立润滑模型.最后,展望MAX/金属基自润滑复合材料的研究前景.

三元层状化合物MAX增强金属基复合材料的研究进展

MAX化合物兼具金属和陶瓷的双重性能,被认为是金属材料较为理想的增强相。本文介绍了MAX化合物增强金属基复合材料的研究现状。

烧结温度对MAX/Cu复合材料的组织及性能影响

以一种典型的MAX相材料Ti_(3)AlC_(2)为原料,采用粉末冶金无压烧结的方式,压坯压力选用500 MPa,烧结时间为1 h,分别选用800、900、1000、1100、1200℃5个烧结温度制备了MAX/Cu复合材料。通过对样品的金相、电导率与显微硬度等测试,探讨了不同烧结温度下MAX/Cu复合材料的组织及其性能变化。结果表明,无压烧结最佳烧结温度为1100℃,可以得到综合性能最佳的复合材料,硬度、致密度和导电率分别达到330 HV、99.5%以上和4.6 m S/m。

CuZr-based bulk metallic glass and glass matrix composites fabricated by selective laser melting

Monolithic bulk metallic glass and glass matrix composites with a relative density above 98%were produced by processing Cu_(46)Zr_(46)Al_(8)(at.%)via selective laser melting(SLM).Their microstructures and mechanical properties were systematically examined.B2 CuZr nanocrystals(30-100 nm in diameter)are uniformly dispersed in the glassy matrix when SLM is conducted at an intermediate energy input.These B2 CuZr nanocrystals nucleate the oxygen-stabilized big cube phase during a remelting step.The presence of these nanocrystals increases the structural heterogeneity as indirectly revealed by mircrohardness and nanoindentation measurements.The corresponding maps in combination with calorimetric data indicate that the glassy phase is altered by the processing conditions.Despite the formation of crystals and a high overall free volume content,all additively manufactured samples fail at lower stress than the as-cast glass and without any plastic strain.The inherent brittleness is attributed to the presence of relatively large pores and the increased oxygen content after selective laser melting.

高性能金属基复合材料研究进展

金属材料因其具备优良的可加工性、导电性、导热性、耐磨耐腐蚀性能,被广泛地应用于医疗、航空、军事等领域,所以研究高性能的金属基复合材料成为复合材料学科的一大热点。目前高性能金属基复合材料的理论制备方法较多,但可用于工业化生产技术方案却相对较少;对单一增强相的研究颇多,多相强化基体的研究较少,这两类矛盾问题突出。文章通过综述金属基复合材料的常用制备方法及其常用增强相的种类与效果,以及对多相强化、稀土调控展开分析,以期为实验探索提供理论依据。

挤压速度对搅拌摩擦反挤压法制备Cu-5%Ti_(2)SnC复合丝材性能的影响

对粉末冶金法制备的含5%(体积分数)Ti_(2)Sn CMAX相的初始复合材料进行搅拌摩擦反挤压(FSBE)处理,研究FSBE工艺的轴向横移速度对Cu-Ti_(2)Sn C复合线材显微组织、力学性能、电学性能和磨损性能的影响。结果表明,随着挤压速度的增加,显微组织中孪晶增多,Ti_(2)SnC颗粒细化,MAX相和Cu基体之间的界面结合改善。当转速为600r/min,轴向横移速度为25mm/min时,Cu-Ti_(2)SnC复合线材具有最大的硬度、屈服强度和极限抗拉强度,分别为HV 132.7、278.34MPa和485.15MPa,这是其更强的界面结合和更细的MAX相导致的。此外,当转速为600 r/min,轴向横移速度为25 mm/min时,Cu-Ti_(2)SnC复合丝的电导率最高,达到89.21%(IACS),磨损率最低,为0.0015 mg/m,这是其更大的晶粒尺寸、更强的界面结合与更低的密度导致的。

Ni-Based Metallic Glass Composites Containing Cu-Rich Crystalline Nanospheres

In this work, a quaternary Ni-Cu-Nb-Ta system has been designed to obtain composite microstructure with sphericalcrystalline Cu-rich particles embedded in amorphous Ni-rich matrix. The alloy samples were prepared by using single-roller melting-spinning method. The microstructure and thermal properties of the as-quenched alloy samples were char-acterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, anddifferential scanning calorimetry. It shows that the spherical crystalline Cu-rich particles are embedded in the amorphousNi-rich matrix. The average size of the Cu-rich particles is strongly dependent upon the Cu content. The effect of the alloycomposition on the behavior of liquid-liquid phase separation and microstructure evolution was discussed. The phaseformation in the Ni-based metallic glass matrix composite was analyzed.