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Effect of equal channel angular extrusion on Al-6063 bending fatigue characteristics

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International Journal of Minerals,Metallurgy and Materials 2015年第4期22卷 395-404页

作者： J.Nemati g.h.majzoobi S.Sulaiman B.T.h.T.Baharudin M.A.Azmah hanim Department of Mechanical and Manufacturing Engineering University Putra Malaysia Engineering Faculty Bu-Ali Sina University School of Mechanics Islamic Azad UniversityTakestan Branch

The purpose of this investigation was to refine the grains of annealed 6063 aluminum alloy and to improve its yield stress and ul- timate strength. This was accomplished via the equal channel angular extrusion （ECAE） process at a temperature of 200℃ using route A, with a constant ram speed of 30 mm/min through a die angle of 90° between the die channels for as many as 6 passes. The experiments were conducted on an Avery universal testing machine. The results showed that the grain diameter decreased from 45 μm to 2.8 μm after 6 extru- sion passes. The results also indicated that the major improvement in fatigue resistance occurred after the first pass. The subsequent passes improved the fatigue life but at a considerably lower rate. A maximum increase of 1100% in the case of low applied stresses and an ap- proximately 2200% increase in fatigue resistance in the case of high applied stresses were observed after 5 passes. The improvement of fa- tigue resistance is presumed to be due to （1） a reduction in the size and the number of Si crystals with increasing number of ECAE passes, （2） the aggregation of Cu during the ECAE process, （3） the formation and growth of CuA12 grains, and （4） grain refinement of the A1--6063 alloy during the ECAE process.

关键词： aluminum alloys equal channel angular pressing bending fatigue life grain size microstructure

Improvements in the microstructure and fatigue behavior of pure copper using equal channel angular extrusion

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International Journal of Minerals,Metallurgy and Materials 2014年第6期21卷 569-576页

作者： J.Nemati g.h.majzoobi S.Sulaiman B.T.h.T.Baharudin M.A.Azmah hanim Department of Mechanical and Manufacturing Engineering Universiti Putra Malaysia School of Mechanics Islamic Azad UniversityTakestan Branch348194 9479 Takestan Iran

In this study, annealed pure copper was extruded using equal channel angular extrusion （ECAE） for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applied stresses using fatigue tests, fractography, and metallography. The mechanical properties of the extruded material were obtained at a tensile test velocity of 0.5 mm/min. It was found that the maximum increase in strength occurred after the 2nd pass. The total increase in ultimate strength after eight passes was 94%. The results of fatigue tests indicated that a significant improvement in fatigue life occurred after the 2nd pass. In subsequent passes, the fatigue life con-tinued to improve but at a considerably lower rate. The improved fatigue life was dependent on the number of passes and applied stresses. For low stresses （or high-cycle fatigue）, a maximum increase in fatigue resistance of approximately 500%was observed for the extruded material after eight passes, whereas a maximum fatigue resistance of 5000%was obtained for high-applied stresses （or low-cycle fatigue）. Optical microscopic examinations revealed grain refinements in the range of 32 to 4 μm. A maximum increase in impact energy absorption of 100%was achieved after eight passes. Consistent results were obtained from fractography and metallography examinations of the ex-truded material during fatigue tests.

关键词： copper equal channel angular extrusion fatigue of materials grain size grain refinement fracture toughness

粉末冶金Mg−B4C复合材料的准静态、动态力学性能及磨损行为

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Transactions of Nonferrous Metals Society of China 2021年第2期31卷 371-381页

作者： K.RAhMANI g.h.majzoobi g.EBRAhIM-ZADEh M.KAShFI Mechanical Engineering Department Bu-Ali Sina UniversityHamedan 65174Iran Department of Soil Science Faculty of AgricultureGuilan UniversityRasht ***Iran Mechanical Engineering Department Ayatollah Boroujerdi UniversityBoroujerd ***Iran

制备体积分数分别为0、1.5%、3%、5%和10%B4C颗粒增强Mg金属基复合材料,研究其力学性能和磨损行为。在450℃和不同加载速率下,分别采用分离式霍普金森棒(ShB)、锻锤(Dh)和Instron(QS)制备Mg−B4C样品,其应变速率分别为1600、800和0.008 ... 详细信息

制备体积分数分别为0、1.5%、3%、5%和10%B4C颗粒增强Mg金属基复合材料,研究其力学性能和磨损行为。在450℃和不同加载速率下,分别采用分离式霍普金森棒(ShB)、锻锤(Dh)和Instron(QS)制备Mg−B4C样品,其应变速率分别为1600、800和0.008 s−1。研究Mg−B4C复合材料的显微硬度、准静态及动态抗压强度等力学性能和磨损性能。结果显示,ShB和Dh样品的硬度分别比QS样品高20.2%和5.7%。ShB法制备的Mg−10.0%B4C样品的磨损率和磨损质量损失分别比QS样品的低33%和39%。与纯Mg相比,ShB、Dh和QS制备的Mg−5.0%B4C样品的准静态抗压强度分别提高39%、30%和29%。此外,含B4C样品的动态抗压强度比准静态抗压强度提高51%~110%。

关键词：粉末压制高应变速率 Mg–B4C复合材料硬度力学性能磨损行为

Fabrication and mechanical properties of MWCNTs-reinforced aluminum composites by hot extrusion

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Rare Metals 2012年第4期31卷 372-378页

作者： Mortazavi Majid majzoobi g.h. golikand A.Noozad Reihani A. Mortazavi S.Z. gorji M.S. Department of Mechanical Engineering Faculty of EngineeringBu-Ali Sina UniversityHamedanIran Department of Materials Engineering Monash UniversityClaytonVictoria 3800Australia Material Research School Tehran P.O.Box 31485-498Iran School of Materials Engineering Najafabad BranchIslamic Azad UniversityIsfahanIran School of Materials and Mineral Resources Engineering Universiti Sains MalaysiaPenangMalaysia

Over the past decade,the interest in aluminum composites reinforced with carbon nanotubes has grown significantly.Studies have been carried out to overcome problems with uniform dispersion,interfacial bonding,void formation and carbide formation of the composites.In the present work,multi-wall carbon nanotubes(MWCNTs) aluminum composites were produced.high-energy ball milling with the aim at developing well-dispersed MWCNTs Al composites was followed by cold compaction,sintering,and hot extrusion at 500 ℃.Different amounts of stearic acid as processing control agent(PCA) is used in order to minimize cold welding of the Al particles,and to produce finer particles.Differential scanning calorimetry(DSC),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD) were employed to analyze the MWCNTs,the aluminum powder,and the composites’ microstructural behavior.The hardness and tensile properties of the composites are also evaluated.The results showed 500% increase in yield stress after the addition of 1 wt% MWCNTs in Al-MWCNTs based composite.The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.

关键词： aluminum matrix composite multi-wall carbon nanotubes(MWCNTs) ball milling mechanical properties