搅拌法铸造空心微珠-铝复合材料组织和性能的研究

采用半固态搅拌铸造法制备了铝-空心微珠复合材料，分别对金属型铸造和挤压铸造方法制备的铝-空心微珠复合材料的组织和性能进行了研究，并对其拉伸断口形貌进行了扫描电镜分析。结果表明：两种铸造方法制备的复合材料的抗拉强度都低于基体铝合金，随着空心微珠加入量的增加，复合材料的抗拉强度有所降低，密度减小，比强度增大，韧性降低，使复合材料的断裂形态从塑性断裂发展为脆性断裂。     

粉末冶金法制备纳米碳管／铝复合材料的力学性能

采用粉末冶金法制备纳米碳管/铝基复合材料,研究不同质量分数纳米碳管对复合材料力学性能的影响.通过X射线衍射仪(XRD)和扫描电镜(SEM)对复合材料及其断口进行分析.结果表明,纳米碳管能细化复合材料的晶粒组织,明显提高复合材料的硬度和抗拉强度.含质量2%纳米碳管复合材料的硬度和抗拉强度达到54HV和121.5MPa,分别比铝基体提高了约80%和28%.复合材料的断口形貌显示,纯铝的断裂方式为微孔聚集型韧性断裂,而2%CNT/Al复合材料具有微孔聚集型和解理型脆性断裂的混合特征.     

不同铸造方法下废玻璃-铝基复合材料的组织和性能

采用半固态搅拌铸造法制备了废玻璃-废铝复合材料,分别对金属重力铸造和挤压铸造方法制备得到的该复合材料的组织和性能进行了研究,并对其拉伸断口形貌进行了扫描电镜分析。结果表明:随玻璃加入量的增加,复合材料的抗拉强度、硬度均先上升后下降,磨损量先下降后上升。该复合材料韧性降低,使其断裂形态从塑性断裂转变为脆性断裂。     

热挤压对内氧化法制备Cu-Al2O3组织性能的影响

采用一种新型简化内氧化工艺结合热挤压工艺,制备了Cu-Al2O3复合材料.对热挤压后复合材料的微观组织和硬度、抗拉强度和电导率进行了研究.结果表明,热挤压明显细化了复合材料的组织,提高了组织均匀性,减少了孔隙等粉末烧结缺陷,得到了较为致密的Cu-Al2O3复合材料;密度达到8.82 g·cm-3;热挤压后其硬度、抗拉强度和电导率显著提高,分别达到HV111、242 MPa、40.6 MS/m.拉伸断口分析表明,烧结态和挤压态断口均为韧窝聚集型断裂,热挤压改善了烧结态的韧性.     

粉煤灰微珠增强铝基复合材料的断裂力学行为

对粉煤灰微珠增强铝基复合材料的力学性能进行了研究,并对其拉伸断口形貌进行了扫描电镜观察.研究结果表明,复合材料的抗拉强度高于纯铝,随着粉煤灰微珠加入量的增加,复合材料的抗拉强度不断增加,但塑性下降.复合材料的断口出现较明显的"河流花样" 和撕裂棱,断裂形态由塑性断裂向脆性断裂转化.     

CNTs含量对CNTs/Al5083复合材料力学性能的影响

利用高能球磨和冷压烧结工艺制备出碳纳米管（CNTs）增强Al5083复合材料,并对球磨过程中CNTs的演变及成型后复合材料的力学性能和形貌进行研究。结果表明,在球磨过程中,通过机械力的作用下带动钢球将CNTs切断,长径比变小,并均匀地分散在Al基体中;在CNTs含量为2wt%下,复合材料抗拉强度和屈服强度分别达到294和239 MPa,硬度达到95 HV5,复合材料的力学性能最好。通过观察复合材料的断口,随着碳纳米管含量的增加,复合材料的断口形貌从韧性断裂向脆性断裂转变。     

热处理对原位(ZrB_2+TiB_2)增强AlSi9Cu3复合材料组织和性能的影响

采用Al-K2Ti F6-K2ZrF6-KBF4体系制备(ZrB_2+TiB_2)二元纳米颗粒增强AlSi9Cu3基复合材料,并对其进行热处理,研究了颗粒加入量对复合材料组织与性能的影响。结果表明,确定的优选颗粒加入量为3.14%;铸态抗拉强度和伸长率分别为265 MPa和14.8%;时效处理后,复合材料的强度略有上升。经过T6和T7热处理后强度有了大幅度提升,拉伸断口呈明显的韧性断裂形式,T7处理的拉伸断口韧窝较清晰、伸长率高于T6。     

Si对SiC_p/Al-Si复合材料抗拉强度与断口形貌的影响

研究了基体中Si含量对铝基复合材料抗拉强度的影响,并对断口形貌与抗拉强度的关系进行了分析。结果表明,随着基体中Si含量的增加,以亚共晶、共晶和过共晶Al-Si合金为基体的SiCP增强铝基复合材料的抗拉强度是逐渐降低的。通过对断口形貌分析发现,随着基体中Si含量的增加,代表塑性断口特征的"韧窝"数量逐渐减少;代表脆性断口特征的"小平面"逐渐增多。通过对小平面进行能谱分析发现,小平面主要由3种相组成:SiCp、Si相、Al8FeMg3Si6相。     

热压烧结-热挤压复合工艺制备SiCp/6061Al基复合材料

采用热压烧结-热挤压复合工艺制备了SiC体积分数为35%的SiCp/6061Al基复合材料。观察了复合材料的金相组织和断口形貌,检测了复合材料的密度和抗拉强度。分析了热压和热挤压复合工艺对复合材料的影响。结果表明:采用热挤压二次成形后,增强体在基体中的分布均匀化,与挤压方向平行;复合材料的致密度达到98.09%,抗拉强度达到248 MPa;基体组织晶粒细化,并产生大量的位错和亚晶组织;SiCp/6061Al复合材料断裂机理主要由6061Al基体的韧性断裂和增强体SiC颗粒的脆性断裂组成。     

喷射沉积SiC/Al-Fe-V-Si复合材料的组织与力学性能研究

研究了沉积态、热压态和热压+轧制态体育器材用Si C/Al-Fe-V-Si复合材料的显微组织和力学性能,并对拉伸断口形貌进行了观察。结果表明:喷射沉积态、热压态和热压+轧制态复合材料主要由α-Al、β-Si C和Al_(12)(Fe,V)_3Si相组成,并没有出现其它高温条件下容易出现的θ-Al_(13)Fe_4脆性相的衍射峰;经过热压以及热压+轧制处理后Si C/Al-Fe-V-Si复合材料的抗拉强度和断后伸长率都相对于沉积态得到不同程度的提高;热压态复合材料的断裂方式为局部韧性和整体脆性的混合断裂,而热压+轧制复合材料的断裂方式为韧性断裂。     

粉煤灰/铝-镁合金复合材料的微观组织及摩擦磨损性能

采用粉末冶金法制得粉煤灰/Al-25%Mg复合材料,研究不同粉煤灰含量对复合材料微观组织、硬度和摩擦磨损性能的影响,采用扫描电子显微镜观察复合材料的磨损表面形貌,并对其磨损机制进行探讨。结果表明:随着粉煤灰含量的增加,复合材料的硬度呈现先增大而后减小的趋势;在较低粉煤灰含量和较低载荷下,该复合材料的摩擦因数均低于基体铝合金的,并且随粉煤灰含量的增加复合材料的耐磨性有所提高,复合材料的磨损机制主要为粘着磨损和磨粒磨损;在较高粉煤灰含量和较高载荷下,该复合材料的磨损机制转化为以剥层磨损和磨粒磨损为主。     

电厂飞灰颗粒增强铝基复合材料的摩擦磨损行为

对挤压铸造制成的飞灰颗粒增强ZL109复合材料在不同条件下的的摩擦磨损行为进行了研究。结果表明：飞灰颗粒的加入可提高铝合金材料的耐磨性,复合材料同基体合金相比,摩擦因数也较低。在摩擦磨损过程中,在较低载荷下复合材料的摩擦表面形成一稳定的摩擦转移层,该转移层的存在可以起到降低摩擦因数的作用。在较高载荷下由于该摩擦转移层遭到破坏,从而影响了其减摩作用的发挥。镶嵌在基体中的飞灰颗粒在摩擦过程中主要起到承受载荷、限制对磨材料与铝基体直接接触的作用。脱落的飞灰颗粒可以起到“滚珠”的作用,在摩擦表面形成“三体”摩擦,从而起到减摩的作用。     

Correlation between tensile and indentation behavior of particle-reinforced metal matrix composites: an experimental and numerical study

The correlation between tensile and indentation behavior in particle-reinforced metal matrix composites (MMCs) was examined. The model composite system consists of a Al–Cu–Mg alloy matrix reinforced with SiC particles. The effects of particle size, particle volume fraction, and matrix aging characteristics on the interrelationship between tensile strength and macro-hardness were investigated. Experimental data indicated that, contrary to what has been documented for a variety of monolithic metals and alloys, a simple relationship between hardness and tensile strength does not exist for MMCs. While processing-induced particle fracture greatly reduces the tensile strength, it does not significantly affect the deformation under indentation loading. Even in composites where processing-induced fracture was nonexistent (due to relatively small particle size), no unique correspondence between tensile strength and hardness was observed. At very low matrix strengths, the composites exhibited similar tensile strengths but the hardness increased with increasing particle concentration. Fractographic analyses showed that particle fracture caused by tensile testing is independent of matrix strength. The lack of unique strength–hardness correlation is not due to the particle fracture-induced weakening during the tensile test. It is proposed that, under indentation loading, enhanced matrix flow that contributes to a localized increase in particle concentration directly below the indenter results in a significant overestimation of the overall composite strength by the hardness test. Micromechanical modeling using the finite element method was used to illustrate the proposed mechanisms under indentation loading and to justify the experimental findings.     

Mechanical Properties of Squeeze-Cast A356 Composites Reinforced With B4C Particulates

In this study, different volume fractions of B₄C particles were incorporated into the aluminum alloy by a mechanical stirrer, and squeeze-cast A356 matrix composites reinforced with B₄C particles were fabricated. Microstructural characterization revealed that the B₄C particles were distributed among the dendrite branches, leaving the dendrite branches as particle-free regions in the material. It also showed that the grain size of aluminum composite is smaller than that of monolithic aluminum. X-ray diffraction studies also confirmed the existence of boron carbide and some other reaction products such as AlB₂ and Al₃BC in the composite samples. It was observed that the amount of porosity increases with increasing volume fraction of composites. The porosity level increased, since the contact surface area was increased. Tensile behavior and the hardness values of the unreinforced alloy and composites were evaluated. The strain-hardening behavior and elongation to fracture of the composite materials appeared very different from those of the unreinforced Al alloy. It was noted that the elastic constant, strain-hardening and the ultimate tensile strength (UTS) of the MMCs are higher than those of the unreinforced Al alloy and increase with increasing B₄C content. The elongation to fracture of the composite materials was found very low, and no necking phenomenon was observed before fracture. The tensile fracture surface of the composite samples was indicative of particle cracking, interface debonding, and deformation constraint in the matrix and revealed the brittle mode of fracture.     

Optimizing Ceramic Preform Properties for Liquid Metal Infiltration

In this paper, a methodology to optimize the production technique and properties of fly ash porous preforms, for liquid metal infiltration, is introduced. The preforms were produced by mixing fly ash with acid phosphate binder and acetone as liquid carrier, at varying compositions. The homogeneity of the green product was determined by micro computed tomography (μCT) and scanning electron microscopy. The effect of binder quantity, porosity, and compaction pressure of the preforms on the resulting bending strength was investigated and considered as one of the criterions for the production of crack-free metal matrix composites (MMCs). Finally the quality of the MMCs, resulting by liquid metal infiltration of the optimized preforms, was examined by μCT to locate micro cracks and uniaxial compression to determine variations in their compressive strength.     

MANUFACTURING OF ALUMINUM/FLY ASH COMPOSITE WITH LIQUID REACTIVE SINTERING TECHNOLOGY

The Al/fly ash composites are fabricated by liquid reactive sintering P/M process with fly ash particles as intensifying phases. The reactivity and newly formed phases during liquid sintering process have been analyzed by combing Thermochemicdl data base calculation and XRD characterization. The results show that some of constituents in fly ash have reacted with liquid aluminum so that the elemental Si, Fe, Ti as well as some amount of intermetallic compounds occur. The properties of aluminum/fly ash composites have been improved. With the fraction of fly ash increase, the composite density decreases; the hardness and the modulus of the composite increases, and the composite wear resistance are significantly increased. The fly ash reinforced composites represent a sort of low cost product with possible widespread applications in the automotive, small engine, and electromechanical machinery sectors.     

陶瓷颗粒增强泡沫铝材料的研究

选用粉煤灰作为增强相,经X射线衍射分析,粉煤灰中主要成分为石英和莫来石,是一种坚硬的陶瓷颗粒。这种陶瓷颗粒起到了增粘作用,并且还有利于提高气泡的稳定性。将粉煤灰加入到熔融铝液中,经适当搅拌后,再加入发泡剂,经冷却,即可得到颗粒增强泡沫铝。利用粉煤灰颗粒增黏的泡沫铝与利用钙增黏的泡沫铝进行压缩强度性能检测。结果表明:粉煤灰不但有增黏作用,还由于石英与铝液发生原位反应生成的氧化物,以及粉煤灰中原有的莫来石起到颗粒增强作用。     

添加NH_4AlO（OH）HCO_3原位生成Al_2O_3/Al复合材料的制备及其性能

碳酸铝铵与熔融的铝液反应原位生成颗粒增强铝基复合材料,对复合材料的力学性能和摩擦磨损行为进行研究。结果表明：在搅拌的铝熔体中碳酸铝铵发生分解反应生成γ-Al2O3;该原位反应的增强颗粒比直接添加的Al2O3在铝熔体中分布得更均匀;复合材料的密度和硬度随着增强相加入量的增加而提高,而强度则随着增强相加入量的增加而降低;磨损率随着增强相加入量的增加和载荷的增加而提高;原位反应生成的复合材料的力学性能和耐磨性明显优于直接添加Al2O3颗粒形成的复合材料的。     

Effect of Fly Ash Particles on the Compressive Properties of Closed-Cell Aluminum Foams

The closed-cell aluminum foam reinforced by 1.5 and 3.0 wt.% fly ash particles were manufactured by molten body transitional foaming process. The backscattered electron image shows that fly ash particles distribute uniformly in the cell wall. The quasi-static compression tests were conducted. Results show that Al/Fly ash foams have stable compressive property and the sudden stress drop was not observed. The plateau stress increases nearly linearly with relative density. Moreover, the addition of fly ash particles improves the plateau stress. Also, the energy absorption property of Al/Fly ash foams increase with relative density and fly ash content. These can be attributed to the contribution of the compression of cell gas and the membrane stress in the cell wall.     

Enhanced Mechanical Properties of AA5083 Matrix Composite via Introducing Al0.5CoCrFeNi Particles and Cryorolling

High-entropy alloy particles (HEAPs) can markedly enhance the mechanical properties of metal matrix composites (MMCs). In this study, AA5083/Al_0.5CoCrFeNi HEAPs MMCs with different HEAPs contents (0, 1, and 3 wt%) were prepared via a stir-casting, and then these MMCs sheets were hot rolled (573 K) and cryorolled (77 K), respectively. The mechanical properties of the MMCs sheets were measured by tensile testing and microhardness test. Additionally, their microstructures were analyzed by scanning electron microscopy and transmission electron microscopy. Results revealed that the ultimate tensile strength (UTS) of the as-cast AA5083/Al_0.5CoCrFeNi HEAPs MMCs were improved from 203 to 257 MPa by adding 3 wt% HEAPs. And the mechanical properties of the MMCs sheets were improved after cryorolling. After cryorolling with 50% rolling reduction ratio, the MMCs with 1 wt% HEAPs had an UTS of 382 MPa, which was 1.9 times that of the MMCs before rolling. Finally, the strengthening mechanisms of HEAPs and cryorolling on the AA5083/HEAPs MMCs were discussed.