In-situ fabrication of particulate reinforced aluminum matrix composites under high-frequency pulsed electromagnetic field

Pulsed magnetic field is generated when imposing pulse signal on high-frequency magnetic field. Distribution of the inner magnetic intensity in induction coils tends to be uniform. Furthermore oscillation and disturbance phenomena appear in the melt. In. situ Al2O3 and Al3Zr particulate reinforced aluminum matrix composites have been synthesized by direct melt reaction using AlZr（CO3）2 components under a foreign field. The size of reinforced particulates is 2-3 μm. They are well distributed in the matrix. Thermodynamic and kinetic analysis show that high-frequency pulsed magnetic field accelerates heat and mass transfer processes and improves the kinetic condition of in-situ fabrication.

Compressive response and microstructural evolution of in-situ TiB_(2)particle-reinforced 7075 aluminum matrix composite

The hot forming behavior,failure mechanism,and microstructure evolution of in-situ TiB_(2)particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300−450℃ and strain rates of 0.001^(−1)s^(−1).The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate,and dimple rupture of the matrix at high temperature and low strain rate.Full dynamic recrystallization,which improves the composite formability,occurs under conditions of high temperature(450℃)and low strain rate(0.001 s^(−1));the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite.Based on the flow stress curves,a constitutive model describing the relationship of the flow stress,true strain,strain rate and temperature was proposed.Furthermore,the processing maps based on both the dynamic material modeling(DMM)and modified DMM(MDMM)were established to analyze flow instability domain of the composite and optimize hot forming processing parameters.The optimum processing domain was determined at temperatures of 425−450℃ and strain rates of 0.001−0.01 s^(−1),in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.

In-situ homogeneous synthesis of carbon nanotubes on aluminum matrix and properties of their composites

Using nickel catalyst supported on aluminum powders, carbon nanotubes （CNTs） were successfully synthesized in aluminum powders by in-situ chemical vapor deposition at 650 ℃. Structural characterization revealed that the as-grown CNTs possessed higher graphitization degree and straight graphite shell. By this approach, more homogeneous dispersion of CNTs in aluminum powders was achieved compared with the traditional mechanical mixture methods. Using the in-situ synthesized CNTs/Al composite powders and powder metallurgy process, CNTs/Al bulk composites were prepared. Performance testing showed that the mechanical properties and dimensional stability of the composites were improved obviously, which was attributed to the superior dispersion of CNTs in aluminum matrix and the strong interfacial bonding between CNTs and matrix.

Study on Processing Conditions of Aluminum Matrix Composites Reinforced with Boron Carbide Particles

Different pre-heating of boron carbide particles for reinforcement and different processing conditions were studied in this work. Being one of the most cost-effective industrial methods, conventional melt stir-casting route was utilized.Result showed that the boron carbide particles distributed well for a suitable pre-heating temperature and processed in air.No reaction product was found at the A1-B4C interfaces at the resolution limit of SEM used in that way.

Microscopic stresses in carbon nanotube reinforced aluminum matrix composites determined by in-situ neutron diffraction

One of the most desired strengthening mechanisms in the carbon nanotube reinforced aluminum matrix composites(CNT/Al)composites is the load transfer strengthening mechanism(LTSM).However,a fundamental issue concerning the LTSM is that quantitative measurements of load partitioning in these composites during loading are very limited.In this study,in-situ neutron diffraction study on the tensile deformation of the 3 vol.%CNT/2009 Al composite and the unreinforced 2009 Al alloy was conducted.The{311}and{220}diffraction elastic constants(DECs)of the 2009 Al alloy were determined.Using those DECs the average stress in the 2009 Al matrix of the composite was calculated.Then the average stress in the CNTs was separated by using the stress equilibrium condition.Computational homogenization models were also applied to explain the stress evolution in each phase.Predicted results agree with experimental data.In the present case,the average stress in the CNTs reaches 1630 MPa at the yield strength of the composite based on linear regression of the measured data,which leads to an increment of yield strength by about 37 MPa.As the result of this work,an approach to quantify load partitioning in the CNTs is developed for the CNT/Al composites,which can be applied to optimize the mechanical properties of the composites.

Microstructures and mechanical properties of in-situ TiB2/Al−xSi−0.3Mg composites

In-situ 2 vol.%TiB2 particle reinforced Al−xSi−0.3Mg(x=7,9,12,15 wt.%)composites were prepared by the salt−metal reaction,and the microstructures and mechanical properties were investigated.The results show that the TiB2 particles with a diameter of 20−80 nm and the eutectic Si with a length of 1−10μm are the main strengthening phases in the TiB2/Al−xSi−0.3Mg composites.The TiB2 particles promote grain refinement and modify the eutectic Si from needle-like to short-rod shape.However,the strengthening effect of TiB2 particles is weakened as the Si content exceeds the eutectic composition,which can be attributed to the formation of large and irregular primary Si.The axial tensile test results and fractography observations indicate that these composites show more brittle fracture characteristics than the corresponding alloy matrixes.

Effect of Hot-Plate Rolling on the Microstructure Evolution and Mechanical Properties of In-Situ Nano-TiC_(P)/Al-Mg-Si Composites

The hot-plate rolling(HPR)process is adopted to achieve the optimal strength-ductility for the in-situ nano-TiC_(P)/Al-Mg-Si composites.There was no crack in the sheet by single pass of hot-plate rolling with a thickness reduction of 80%,while there were numerous cracks in the sheet by two passes of conventional hot rolling to achieve a total reduction of 50%.The microstructure and mechanical properties of the composites subjected to 80%thickness reduction of hot rolling at 540℃were investigated by tensile tests,scanning electron microscopy,and electron backscatter diffraction.The yield strength and ultimate tensile strength of in-situ nano-TiC_(P)/Al-Mg-Si composites after the hot-plate rolling process and T6 heat treatment increased significantly due to the dislocation strengthening and precipitation strengthening.

Microstructural Characterization and Tensile Behavior of Rutile(TiO_2)-Reinforced AA6063 Aluminum Matrix Composites Prepared by Friction Stir Processing

Rutile(TiO_2) particle-reinforced aluminum matrix composites were prepared by friction stir processing. The microstructure was studied using conventional and advanced characterization techniques. TiO_2 particles were found to be dispersed uniformly in the composite. Clusters of TiO_2 particles were observed at a higher particle content of 18 vol%. The interface between the TiO_2 particle and the aluminum matrix was characterized by the absence of pores and reactive layer.Sub-grain boundaries, ultra-fine grains and dislocation density were observed in the composites. TiO_2 particles improved the mechanical properties of the composites. However, a drop in tensile strength was observed at a higher particle content due to cluster formation. All the prepared composites exhibited ductile mode of fracture.

Preparation of Aluminum Matrix Composite by Pressureless Infiltration Process

he Al_2O_3 particle reinforced aluminum matrix composite was prepared by using a new pressureless infiltration process. The microstructure of (Al_2O_3)p/Al was analyzed. The tension and the thermal conductivity of the composite were studied as well.

On the liquid-phase technology of carbon fiber/aluminum matrix composites

The main problems with the liquid-phase technology of carbon fiber/aluminum matrix composites include poor wetting of the fiber with liquid aluminum and formation of aluminum carbide on the fibers’surface.This paper aims to solve these problems.The theoretical and experimental dependence of porosity on the applied pressure were determined.The possibility of obtaining a carbon fiber/aluminum matrix composite wire with a strength value of about 1500 MPa was shown.The correlation among the strength of the carbon fiber reinforced aluminum matrix composite,the fracture surface,and the degradation of the carbon fiber surface was discussed.

Fabrication of AA7005/TiB2-B4C surface composite by friction stir processing: Evaluation of ballistic behaviour

The present work aims to enhance the ballistic resistance of AA7005 alloy by incorporating the TiB2 and B4C ceramic reinforcement particles. Surface composites with different weight fractions of TiB2 and B4C particles were processed by friction stir processing. Micro-hardness and depth of penetration tests were carried out to evaluate the ballistic properties of the surface composites. The surface hardness of the composite was found to be nearly 70 HV higher than base alloy. The depth of penetration of the steel projectile was 20e26mm in the composites as compared to 37mm in the base alloy. Ballistic mass efficiency factor of the surface composite was found to be 1.6 times higher than base alloy. This is mainly attributed to the dispersion strengthening from the reinforcement particles.

Fabrication,microstructure and mechanical properties of Mg matrix composites reinforced by high volume fraction of sphere TC4 particles

A novel liquid settling method was investigated and applied to fabricate TC4 spherical particle reinforced AZ91 alloy matrix composites.This method was called liquid state settling technique in which TC4 particles would settle down under the force of gravity.High volume fraction(50%)particle reinforced AZ91 composites could be easily obtained via this novel method.This is difficult to achieve for other traditional liquid fabrication methods.In addition,there was a good dispersion of TC4 particles in the AZ91 matrix and no clusters were found,which indicate that this method was feasible.Interfacial reaction occurred and the reaction product was confirmed to be Al2Ti.Three kinds of pre-dispersion technologies were used before the settling process and different interfacial microstructures were found.Theoretical calculation and experimental results both indicated that the interfacial product which was embedded in the matrix strengthened the composites and improved the tensile strength.

In situ prepared Al-Si alloy matrix composites reinforced by γ-Al_2O_3p

A γ-Al2O3 particles reinforced Al-Si alloy matrix composite was fabricated by adding NH4Al（SO4）2 to molten aluminum alloy. TEM observation shows that in-situ γ-Al2O3 particles are generally spherical and uniformly distributed in the matrix. The results of dry sliding wear tests show that the wear resistance of the composites increases with increasing mass fraction, and the volume loss is considerably lesser than that of the matrix and is lesser than that of the composites by adding γ-Al2O3 particles directly.

Identification of Optimum Composition and Mechanical Properties of Al-Ni Metal Matrix Composite

Composites are materials that are made up of two or more chemically dissimilar phases. In this project aluminum was chosen as matrix material because it was inexpensive, light-weight, strong, tough and corrosion resistant. For the main load bearing phase it was hard, corrosion resistant at room temperature and thermally stable. The stir casting method was used because it was cost-effective and easy, and the particulate reinforcement (nickel) was uniformly distributed throughout the matrix phase. Sand moulding was used to cast the specimens. Specimens with 10, 20, 30 and 40 percentage Nickel were tested and the optimal specimen contained 20% Nickel. The Brinell hardness of Al + 20% Ni increased by 14.80%, Rockwell hardness increased by 2.43%, ultimate tensile strength increased by 1.003% and thermal conductivity of Al + 20% Ni decreased by 24.98% with respect to Aluminum.

Preparation of NiTip/Al composites with controllable phase transformation and damping behavior by friction stir processing

The NiTip/1060Al composites were prepared using a pre-aging and friction stir method(FSP)to enhance the low-temperature damping performance of the aluminum alloy and accommodate various service temperatures.The bonding between NiTi particles and the 1060Al matrix is well established after FSP,and no new phases are formed in the composites.The phasetransformation peak temperature of NiTip/1060Al composites gradually shifts to lower temperatures with increased aging temperature of NiTi particles.At room temperature,the 550℃-NiTip/1060Al composite exhibits superior damping performance,with an internal friction value 144%higher than that of the FSP-1060Al alloy.However,at-91℃,the 650℃-NiTip/1060Al composite demonstrates better damping performance,with an internal friction value 158%higher than that of the FSP-1060Al alloy.The NiTip/1060Al composites exhibit the internal friction peak of NiTi phase-transformation in the temperature range from-91℃to 60℃.This characteristic results in significantly better damping performance compared to the FSP-1060Al alloy and other high-damping aluminum matrix composites.

正交三向织物增强铝基复合材料的高温拉伸力学行为与失效机理

针对真空压力浸渗制备的正交三向织物增强铝基复合材料,采用实验与数值模拟方法研究了高温(400℃)下的准静态拉伸力学响应及损伤演化与失效行为;根据纱线微观组织和织物结构分别建立了微观和细观尺度代表性单胞,基于组分材料的温度相关的性能参数构建微观单胞有限元模型,计算获得不同温度下纱线的横向和轴向力学性能,进而采用包含基体、纱线、界面的细观单胞有限元模型分析了复合材料热应力和高温拉伸力学行为。结果表明:室温下复合材料存在与织物结构相关的非均匀分布的残余应力,纳米压痕法测得的残余应力与模拟值基本一致,高温状态下残余应力得到释放并使基体和纱线分别处于压应力和拉应力状态;复合材料的高温拉伸模量、极限强度和断裂应变的实验均值分别为107.1 GPa、657.1 MPa和0.78%,均匀化计算的高温拉伸曲线与实验曲线总体上吻合。拉伸初期纱线交织处的基体和界面首先发生损伤,捆绑纱弯曲部位出现局部失效,但复合材料表现出线弹性力学行为。随着拉伸应变增大,捆绑纱和纬纱先后发生断裂,且二者与基体之间的界面出现脱黏现象,拉伸曲线开始表现出非线性特征。拉伸后期经纱失效区域的扩展使得拉伸切线模量明显下降,经纱的轴向断裂最终导致复合材料失去承载能力。数值模拟和断口分析表明,纬纱和捆绑纱因横向开裂而形成较平整的断裂面,经纱轴向断裂后拔出长度参差不齐,其断口存在纤维拔出及其周围基体撕裂破坏的微观特征。

球磨方式对CNTs/Al复合材料显微组织与力学性能的影响

采用湿法球磨和干法球磨两种方式制备碳纳米管(carbon nanotubes,CNTs)和铝的复合粉体,再使用放电等离子烧结结合热挤压的工艺制备碳纳米管增强铝基(CNTs/Al)复合材料,系统研究了制备工艺-组织结构-材料性能之间的关系。结果表明,相较于干法球磨,湿法球磨可以更好地分散碳纳米管,且显著减少对其结构的破坏;乙醇球磨介质具有冷却作用,在减少粉体冷焊的同时有助于细化Al基体晶粒,从而使复合材料获得出色的力学性能。乙醇湿法球磨6 h后烧结并热挤压的2%CNTs/Al复合材料抗拉强度达到207 MPa。

激光粉末床熔融成形金刚石增强铝基复合材料

添加质量分数3%金刚石颗粒并利用激光粉末床熔融技术制备6061铝基复合材料。采用光学显微镜、扫描电子显微镜、X射线衍射仪、电子密度计、电子式万能试验机对3%金刚石/6061铝基复合材料的微观组织、相对密度和拉伸性能进行了表征与分析。结果表明:金刚石与Al基体反应生成了针状Al4C3相,并沉积在α-Al基体上,导致晶界位错密度增加,强度提高,抗失效能力增强。金刚石的添加促使6061铝基体中热裂纹消失,但存在孔洞缺陷。较低的扫描速度增加了激光光斑与被加工材料接触的时间,导致金刚石颗粒部分石墨化,铝基体部分蒸发,进而形成内部缺陷,降低了复合材料的相对密度(97%)。金刚石的加入显著提高了激光粉末床熔融技术成形金刚石/6061铝基复合材料的抗拉强度,当激光功率为350 W、扫描速度为800 mm·s-1时,复合材料的极限抗拉强度达到最大值244.2 MPa,屈服强度211.6 MPa,伸长率2.1%。

高熵合金增强铝基复合材料的研究进展

多主元高熵合金具有优异的综合性能,以其做增强体的铝基复合材料极具研究价值和应用潜力。综述了高熵合金增强铝基复合材料的制备、显微组织和性能的研究进展,并展望了该材料未来的研究方向。

铝合金蒙皮表面漆膜去除工艺对比研究

为对比不同工艺去除铝合金蒙皮表面漆膜的效果及对基体材料的影响,分别采用机械打磨法、喷砂除漆法以及激光除漆法去除铝合金蒙皮表面的漆层,使用扫描电镜、激光共聚焦显微镜、拉曼光谱仪对除漆效果进行了表征。结果表明,机械打磨所用的SiC磨粒不仅会嵌入除漆表面,还会破坏漆层聚合物的化学结构,导致Si、N-H、-CH含量显著增大,无法避免基底损伤。喷砂除漆法的喷砂压力从0.1 MPa分别增大至0.3 MPa、0.5 MPa后,除漆表面冲击凹坑直径增大,表面粗糙度由7.89μm分别增大至14.27μm、13.29μm,误差较大,无法保证再喷漆的工艺质量。激光除漆法可以精细化控制除漆进程,将热输入量控制为50.4 J/cm^(2)时,表面漆层几乎完全去除,且基底表面未见明显损伤。本研究证明,激光除漆作为新兴除漆工艺,具备高效、参数可控、可实时监控等优势,在工业领域具有一定应用价值及发展潜力。