Self-lubricating bidirectional carbon fiber reinforced smart aluminum composites by squeeze infiltration process

Self-lubrication is one of the smart material properties required for producing components with enhanced wear resistance and low coefficient of friction.Bidirectional(BD) satin weave polyacrylonitrile(PAN)based carbon fiber(Cf) fabric preform was successfully infiltrated with Al 6061 alloy by squeeze infiltration process.The infiltrated composite shows uniform distribution of carbon fibers in the matrix with the elimination of porosities,fiber damage and close control on the formation of deleterious aluminum carbide(Al_4C_3) phase.C_f/Al composite exhibits remarkable wear resistance compared to unreinforced alloy due to the formation of self-lubricating tribolayer on the pin surface,which intercepts the contact of matrix metal to counter surface.The BD carbon fiber enhanced the hardness and compressive strength of the composite by restraining the plastic flow behavior of matrix.High resolution transmission electron microscopy shows the presence of Al_2O_3 and MgAl_2O_4 spinel,confirmed by EDS and SAD pattern,at the composite interface.The composite shows a lower density of 2.16 g/cm~3 which is a major ad vantage for weight reduction compared to the monolithic alloy(2.7 g/cm~3).     

High strain rate superplasticity in a nano-structured Al–Mg/SiCP composite severely deformed by equal channel angular extrusion

High strain rate superplastic deformation potential of an Al–4.5%Mg matrix composite reinforced with 10% SiC particles of 3 μm nominal size was investigated. The material was manufactured using powder metallurgical route and mechanical alloying which was then processed by equal channel angular extrusion (ECAE). The composite showed a high resistance to static recrystallization. The manufacturing operations atomized SiC particles to nanoscale particles and the severe plastic deformation process resulted in a dynamically recrystallized microstructure with oxide dispersoids distributed homogeneously throughout the matrix. These particles stabilized the ultra-fine grained microstructure during superplastic (SP) deformation. Testing under optimum conditions at constant strain rates led to tensile elongations >360%, but it could be further increased by control of the strain rate path. Transmission electron microscope (TEM) studies showed that the low angle boundary sub-grain structure obtained on heating to the SP deformation temperature developed on straining into a microstructure containing high angle boundaries capable of sustaining grain boundary sliding.     

增强相Al3Ti状态对Al3Ti /ZL101原位复合材料力学性能的影响

通过正交实验研究的Al3Ti/ZL101原位复合材料的最佳成分重量佰分比为：Mg0.35%,Si7%,Ti3.5%,其制备工艺为在特定温度下,往ZL101基体材料中加入TiO2发生直接反应,形成Al3Ti/ZL101复合材料：在正确的制备工艺下,所生成的增强相Al3Ti的形态为杆状,平均尺寸0．5um左右,均匀弥散地分布于αAl晶粒内部,与基体Z101町比,该Al3Ti/ZL101原位复合材料热处理后的室温强度,硬度及延伸率均有较大提高。     

Graphene oxide effects on the properties of Al_2O_3-Cu/35W5Cr composite

Graphene oxide(GO) nanosheets were dispersed into premixed powders(Cu-0.4 wt% Al/35W5Cr) by wet grinding and vacuum freeze-drying process. The 0.3 wt% GO/Al_2O_3-Cu/35W5Cr and 0.5 wt%GO/Al_2O_3-Cu/35W5Cr composites, used for electrical contacts, were fabricated by vacuum hot-pressing sintering.The microstructure was analyzed by field emission scanning electron and transmission electron microscopy. In addition, the Raman spectroscopy and X-ray photoelectron spectroscopy were used to investigate the structural changes of GO before and after sintering. The arc erosion behavior was investigated by the JF04 C electrical contact testing apparatus. Consequently, the Al_2O_3 nanoparticles were evenly dispersed in the matrix, causing dislocation tangles. GO was converted to reduced graphene oxide after sintering. A group of carbon atoms combined with Cr forming Cr_3C_2 in situ during sintering, which enhanced the interface bonding. Compared with the Al_2O_3-Cu/35W5Cr composite, the tensile strength of the two contact materials containing 0.3 wt% GO and 0.5 wt% GO was increased by 45% and 34%, respectively. Finally, pips and craters were present on the anode and cathode surfaces, respectively.Tungsten has undergone re-sintering during arcing and formed needle-like structures. Compared with Al_2O_3-Cu/35W5Cr, the GO/Al_2O_3-Cu35W5Cr composites have better welding resistance. The final mass transfer direction of the two composites was from the cathode to anode.     

常规铸造工艺条件下SiCp/Al-Si复合材料中的界面反应

采用搅拌复合法制备了10%SiC／Al—5Si—Mg，10%SiC／Al—7Si—Mg(体积分数)复合材料，研究了在常规铸造工艺条件下重熔后复合材料中的界面反应。通过透射电镜和能谱分析可知，SiC界面基本上都是单一的SiC／Al及SiC／Si界面，部分界面上有MgAl2O4颗粒相形成，由于基体合金中Si的存在，生成Al2C3的有害界面化学反应得到了抑制。对不同文献中抑制Al4C3产生所需临界Si含量实验测定结果的差异进行了分析。     

反应热压(Al2O3+TiB2+Al3Ti)/Al复合材料的低周疲劳行为

采用反应热压法以Al、B₂O₃、TiO₂粉和Al、B、TiO₂粉为原料制备了两种(Al₂O₃+TiB₂+Al₃Ti)/Al复合材料。后一种原料粉制备的复合材料从基体中析出了细小的Al₃Ti相。研究了应变控制原位生成复合材料的室温低周疲劳行为。结果表明,在应变幅较小时(ε_</em>t≤0.3%),不含Al₃Ti析出相的材料表现为循环稳定;而在应变幅较大时(ε_</em>t≥0.4%), 则表现为第一周的循环硬化和随后的循环软化。在所采用的应变幅下,含Al₃Ti析出相的材料均表现为循环稳定。疲劳裂纹萌生部位为Al₃Ti相断裂、Al₃Ti相与基体的界面开裂和基体中微裂纹。疲劳裂纹穿过基体,绕过Al₂O₃、TiB₂质点扩展。两种复合材料的疲劳寿命均符合Coffin-Manson公式。      

原位自生Al_2O_3-TiC_p/Al基复合材料的热力学分析

采用熔铸法制备了原位自生Al2O3-TiCp/Al基复合材料。借助差示扫描量热仪(DSC)、扫描电子显微镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)等测试技术,对Al-TiO2-C体系的热力学进行了详尽的分析,讨论了过量铝对Al-TiO2-C体系反应的影响。结果表明,通过控制反应温度等工艺参数完全可以获得原位自生Al2O3-TiCp/Al基复合材料,避免副产物Al3Ti和Al4C3的产生。Al-TiO2-C体系原位合成Al2O3-TiCp/Al基复合材料存在着复杂的化学反应。首先在无过量铝的情况下,Al与TiO2发生置换反应,生成了Al2O3和游离态[Ti],而后游离态[Ti]与C结合生成TiC;而存在过量铝的情况下,首先发生铝热反应生成Al3Ti,进而Al3Ti与C结合生成TiC。最终完全获得Al2O3-TiCp/Al复合材料。随着过量Al含量由0增加至70%,Al与TiO2反应生成Al2O3的反应起始温度不断降低。     

纳米Al_2O_3弥散强化铜复合材料的产业化制备及研究

采用内氧化法以水雾化铜铝粉为原料制备出铝含量(质量分数)分别为0.15%、0.40%、0.60%的Al2O3弥散铜复合材料。研究了Al2O3弥散强化铜材料的组织与性能,结果表明,弥散铜材料的晶粒细小,晶粒大小约为10μm;γ-Al2O3在基体中均匀分布,平均尺寸约为6nm,间距为40nm;挤压态为Al含量0.60%的弥散铜棒材(Φ25mm)不经任何中间热处理,直接冷拉拔即可得到Φ3mm的铜丝,其抗拉强度高达680MPa,电导率达78%IACS。     

Al-Fe2O3体系等离子反应合成金属颗粒增韧复合陶瓷涂层的研究

利用Al-Fe2O3体系放热反应,采用等离子反应合成技术,制备出了金属颗粒增韧的FeAl2O4-Al2O3-Fe复合陶瓷涂层,并研究分析了复合涂层的组织及其性能.结果表明:等离子反应合成得到了以层状基体相FeAl2O4与硬质相Al2O3为骨架,球状Fe相弥散分布于基体相上的复合涂层;所制得的金属/陶瓷复合涂层的韧性得到明显提高,其韧性优于在同样基材上等离子喷涂的陶瓷涂层;特别是复合涂层具有较高的耐磨性能.     

Fabrication and characteristics of in situ Al12W particles reinforced aluminum matrix composites by reaction sintering

A novel in situ Al12W particles reinforced aluminum matrix composite was synthesized by reaction sintering of tungsten and aluminum powders and followed by hot extrusion. The microstructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The tensile tests of composite and pure aluminum materials were measured. The XRD analysis identifies that the in situ Al12W particles are formed by the reaction between tungsten and aluminum powders. Meanwhile, SEM observation shows that the Al12W particles are distributed uniformly in the Al matrix, and TEM observation shows that the interfacial condition of Al12W particles and Al is good. It is found from the tensile tests that the in situ synthesized Al12W particles can significantly enhance the strength of the composite in spite of decreasing elongation. The fracture morphology analysis reveals that the fracture mode of composite is ductile fracture.     

双屏蔽(B4C-W)/6061Al层状复合板设计与性能

基于B₄C和W良好的屏蔽中子和γ射线性能,采用6061铝合金作为基体,设计了一种新型双屏蔽(B₄C-W)/6061Al层状复合材料,通过放电等离子烧结后加热轧制成板材,对制备的复合材料微观组织和力学性能进行了研究。结果表明,屏蔽组元B₄C和W颗粒均匀地分布在6061Al基体中,层界面、B₄C/Al、W/Al异质界面之间结合良好,无空隙和裂纹。在颗粒与基体界面处形成扩散层,扩散层的厚度约为6 μm (W/Al)和4 μm (W/Al)。轧制态的(B₄C-W)/6061Al层状复合板的屈服强度(109 MPa)和极限抗拉强度(245 MPa)明显优于烧结态的复合材料,但断裂韧性降低。强度提高的原因主要是轧制后颗粒的二次分布、均匀性及界面结合强度提高,基体合金的晶粒尺寸减小,位错密度增加。层状复合板的断裂方式为基体合金的韧性断裂和颗粒的脆性断裂。      

SiC_P表面镀Ti改性对SiC_P/Al2014复合材料组织及力学性能的影响

采用盐浴镀的方法对SiC_P进行表面镀Ti处理,并通过搅拌铸造的方法制备了表面镀Ti改性SiC_P/Al2014复合材料。研究了镀Ti SiC_P的尺寸和体积分数对SiC_P/Al2014复合材料微观组织和力学性能的影响规律。结果表明:表面镀Ti处理能有效改善SiC_P在Al基体中的分散均匀性;但随着SiC_P体积分数提高,相同尺寸的镀Ti SiC_P在Al基体分散均匀性逐渐变差,当SiC_P体积分数相同时,其在Al基体中的分散均匀性随着SiC_P尺寸的增加逐渐变好。SiC_P尺寸相同时,SiC_P/Al2014复合材料的常温拉伸强度随颗粒体积分数的增加先增大后减小,SiC_P尺寸为5μm和10μm的SiC_P/Al2014复合材料抗拉强度在颗粒的体积分数为4%时达到最高,分别为524MPa和536MPa;SiC_P/Al2014复合材料的高温(493K)抗拉强度随着SiCp体积分数增加而增大,SiC_P尺寸为5μm和10μm的SiC_P/Al2014复合材料抗拉强度在颗粒体积分数为6%时达到最高,分别为308 MPa和320 MPa。     

6vol%纳米B_4C_P/2009Al复合材料的颗粒分布特征及性能

采用三维高效混料机混料、多级真空热压和热挤压制备了增强体含量为6vol%的纳米B_4C_P(n-B_4C_P,50nm)/2009Al复合材料,研究复合材料中n-B_4C_P分布、形成机制以及对n-B_4C_P/2009Al复合材料力学性能的影响。结果表明:当混料球料比为5∶1时,复合粉末经过30h混料后,纳米B_4C_P基本均匀分布于Al合金颗粒表面;热压态复合材料中n-B_4C_P偏聚在基体晶界处,经过热挤压后,复合材料中的n-B_4C_P呈弥散均匀分布。热挤压过程中,基体合金的塑性流动对分布于晶界处的纳米B_4C_P形成剪切作用力,断裂的纳米B_4C_P团聚体沿着剪切应力方向发生重新分布是实现n-B_4C_P均匀分布的主要机制。经过495℃保温1h后水淬,175℃人工时效16h后,增强体含量为6vol%n-B_4C_P/2009Al复合材料硬度比基体合金提高了36.4%,抗拉强度和屈服强度分别提高10.9%和26.2%。n-B_4C_P/2009Al复合材料的拉伸断口表现出韧性断裂和脆性断裂混合特征。     

原位自生TiB2/Al-4.5Cu复合材料微观组织和力学性能

采用混合盐反应法制备TiB2含量分别为0%,2%,5%,8%(质量分数,下同)的TiB2/Al-4.5Cu复合材料,T6热处理后,采用XRD,ICP,OM,SEM,EDS等测试手段和室温拉伸实验进行微观组织观察和力学性能测试。XRD和ICP测试证实,合金体系中仅含α-Al,Al2Cu及TiB2,无Al3Ti,Al2B等反应中间产物。OM和SEM发现,基体材料中α-Al平均晶粒尺寸为167.5μm,而在2%,5%,8%的TiB2/Al-4.5Cu中,其平均晶粒尺寸依次为110.4,87.2,75.2μm,晶粒细化效果显著。TEM观察发现,TiB2颗粒主要分布在晶界处,呈四方和六方结构。室温拉伸实验表明,随着TiB2含量的增加,强度、显微硬度值均呈增加趋势,但伸长率不断下降。当加入8%TiB2时,屈服强度、抗拉强度、弹性模量和显微硬度分别达到356 MPa,416 MPa,92.5GPa和96.5HV,但其伸长率从10.3%降低到4.3%。载荷传递强化、细晶强化、位错增殖强化是TiB2/Al-4.5Cu复合材料力学性能得以大幅提升的影响因素,尤其是在位错增殖强化作用下,TiB2颗粒周边致密分布的位错胞、位错环对强度的提升起到了决定性作用。     

High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys for Advanced Die-Materials Applications

In this study, we report on advanced Ni3Al based high temperature structural alloys with Zr and B addition in order to apply in the fields of die-casting and high temperature press forming as die materials. Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced by vacuum arc melting were investigated in terms of phase analysis by using a scanning electron microscope （SEM） equipped with an X-ray energy dispersive spectrometer （EDS）, an X-ray diffractometer （XRD） and tensile test. The duplex microstructural feature consisting of γ＇ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole microstructure. The ultimate tensile strength of the present alloy was superior to commercial iron-based and Ni-based die-materials especially in the high temperature region.     

搅拌铸造SiCp/2024复合材料热挤压-轧制变形组织及性能

利用搅拌铸造-热挤压-轧制工艺制备SiCp/2024复合材料薄板。通过金相观察(OM)、扫描电镜(SEM)及力学测试等手段研究了该复合材料在铸态、热挤压态及轧制态下的显微组织及力学性能,分析了材料在塑性变形过程中显微组织及力学性能的演变。结果表明,该复合材料铸坯主要由80～100μm的等轴晶组成,粗大的晶界第二相呈非连续状分布,SiC颗粒较均匀地分布于合金基体中;热挤压变形后,晶粒沿挤压方向被拉长,SiC颗粒及破碎的第二相呈流线分布特征;轧制变形后,基体合金组织进一步细化,晶粒尺寸为30～40μm,SiC颗粒破碎明显,颗粒分布趋于均匀,轧制变形对挤压过程中形成的SiC颗粒层带状不均匀组织有显著的改善作用。数学概率统计指出,塑性变形有利于提高颗粒分布的均匀性。力学测试表明,塑性变形后,复合材料的抗拉强度、屈服强度和延伸率显著提高。SiCp/2024铝基复合材料主要的断裂方式为:合金基体的延性断裂、SiC颗粒断裂及SiC/Al界面脱粘。     

反应形成MoSi2/Al2O3陶瓷复合材料的微观结构

以MoO3、Al和Si为原料,通过控制工艺,用反应烧结法制备MoSi2／Al2O3陶瓷复合材料。通过对M0O3 Al Si在Ar气氛中反应的差热曲线分析来确定烧结MoSi2／Al2O3陶瓷复合材料的热处理工艺。分析了生成的MoSi2／Al2O3陶瓷复合材料的X射线图谱、扫描电镜图和能谱分析图,以确定其微观结构。     

碳化硅纤维增强铝基复合材料的界面组织研究EI

本文利用透射电子显微术（ＴＥＭ）和微区能谱分析（ＥＤＸ）对化学气相沉积碳化硅纤维增强ＬＤ２铝合金的界面结构进行了研究，并对显微组织与性能的关系进行了讨论。结果发现，用热压扩散工艺生产的ＳｉＣ／Ａｌ复合材料，其基体与ＳｉＣ纤维结合良好。界面处有棒状相Ａｌ＿４Ｃ＿３生成（该相是菱形结构，对纤维强度有较大破坏作用），且存在镁元素富集。     

铝合金熔体氧化制备Al2O3 / SiC/ Ni/ Al-Si多相模糊界面陶瓷基复合材料

针对Al₂O₃ / Al 复合材料中金属相Al 对其高温性能的不利影响, 本试验在高温下将铝合金熔体氧化渗透到注浆成型的SiC/ Ni 多孔预制体中, 制备了Al₂O₃ / SiC/ Ni/ Al-Si 多相陶瓷基复合材料。借助光学显微镜、电子显微镜(SEM) 、X 射线衍射仪(XRD) 、波谱仪( EDS) 等手段分析了预制体和复合材料的相组成、微观结构及界面特征。结果表明, 复合材料的主晶相为Al₂O₃ 与SiC , 相间存在Al (Si) 复合氧化物、NiAl₂O₄ 及Ni 与Al-Si 合金相, 各相界面处成分呈连续过渡变化趋势, 构筑了具有模糊界面特征的多相复合材料。      

Microstructure and Mechanical Properties of Hyper-eutectic Al-Si Alloys Fabricated by Spray Casting

Microstructure and mechanical properties of hyper-eutectic Al-Si alloy fabricated by spray casting were in- vestigated and then these results were compared with those by squeeze cast.The spray-cast specimen was found to have finer Si particles （～5μm） compared to the squeeze-cast specimen （10-25μm）.The tensile strength and elongation of the spray-cast specimen are also higher than those of the squeeze cast one.It was considered that the increased mechanical properties of the spray-cast specimen were mainly due to finer size of the Si particles distributed in Al matrix.