Papers by Keyword: Hardness

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Authors: Yang Tao Xu, Tian Dong Xia, Wen Jun Zhao, Xiao Jun Wang
Abstract: Co-Al-W supperalloy used pure element powder, according to the ratio of different atomic percentage composition to make ingredients. It is mixed by planetary ball mill, pressed into blocks after the melting shape. Vacuum arc melting process was prepared by melting, after grinding, polishing, and after a volume of 5% perchloric acid and 95% of the electrolytic etcheing solution prepared in ethanol corrosion observed after analysis of the microstructure and phase composition by XRD analysis .It can be found that Co-Al-W superalloys were mainly composed of cobalt-rich matrix of austenite precipitation of γ phase and coherent with matrix of the L12 structure of γ′-Co3(Al,W) phase. In addition, Nb have effect on grain refinement and refine grain. Rockwell hardness test and analysis, It can be found that Nb can clearly improve the Co-Al-W superalloy hardness.
Authors: Jaroslav Sedláček, Dušan Galusek, P. Švančárek, A. Brown, R. Brydson
Authors: D. Sujan, C.W. Yeo, Muhammad Ekhlasur Rahman, M. Mohan Reddy, Md Abdul Maleque, Mohammad Yeakub Ali
Abstract: Stir casting method is used in the production of SiC reinforced-aluminium metal matrix composite (AMMC) to enhance the properties of base metal. Different weight fraction of Silicon carbide, SiC (5 wt%, 10 wt% and 15 wt %) particulate-reinforced AMMCs are fabricated and characterizations of physical and mechanical properties of the materials are performed based on the experimental. The microstructure of the fabricated composite material are studied and analyzed. The results indicate that the mechanical properties of the composite, including yield strength, tensile strength and hardness are enhanced by the increment of the weight fraction of reinforcing phase. Nevertheless, the elongation and fracture toughness of the composite decreased as the reinforcing phase increased. This is mainly due to the brittleness of the SiC particles which act as micro void initiator.
Authors: Rafidah Razuan, Mohamad Kamal Harun, Mahesh Talari
Abstract: High Entropy Alloy (HEA) with at least 5 elements with equimolar ratios were developed to investigate the characteristics of Zr added in FeNiAlCoCrZrx (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0). HEAs were prepared by arc melting technique in Ar atmosphere and were remelted five times to ensure homogeneity. The microstructure and phase constitution of these alloys are examined by X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM). The results show that addition of Zr to FeNiAlCoCr HEA resulted in multiple solid solution phases viz., BCC1, BCC2, FCC1 and FCC2 as evidenced by XRD patterns. Furthermore, presence of both BCC and FCC phases at higher Zr additions suggests that Zr did not preferentially promoted the solidification of either BCC or FCC phase. It can be observed from the FESEM micrographs that with different Zr additions, solidified microstructures of FeNiAlCoCrZrx alloys varied between completely eutectic microstructures to proeutectic and eutectic phase mixtures. From FESEM micrographs it can be suggested that different Zr contents have resulted in different solidification modes. Hardness of Zr added samples is higher compared to base HEA which is FeNiAlCoCr. It was observed that hardness values are higher when proeutectic phases were present compared to completely eutectic FeNiAlCoCrZr alloy (x=0.1).
Authors: Yustiasih Purwaningrum, Panji Lukman Tirta Kusuma, Dwi Darmawan
Abstract: The aimed of this research is to investigate the effect of T-Joint’s root gap on physical and mechanical properties of weld metal. Low carbon steel were joined in T-joint types using MIG (Metal Inert Gas) with variation of root gap. The root gap used were 0 mm, 3 mm and 6 mm. The physical properties examined with chemical composition, microstructure and corrosion using optical microscope. The mechanical properties were measured with respect to the strength and hardness using Universal testing machine and Vickers Microhardness. The results show that the highest value found in welds with a gap of 3 mm with a value of 163.57 MPa. Hardness value is directly proportional to the tensile strength of the material. The highest value found in welds with root gap of 3 mm, followed by root gap of 6 mm, and 0 mm Hardness values in the welding area is higher than the parent metal and HAZ because the number of Si, Mn and Cu elements in the welding metals are bigger than base metal. Weld with all variation of root gap have a good corrosion resistance because the corrosion rate in welds with various root gap have a value below 0.02 mmpy. Microstructure of weld metals were Accicular ferrite, Widmanstatten ferrite, and grain boundary ferrite, while microstructure of base metal and HAZ were ferrite and perlite.
Authors: Reza Nosouhi, Saeed Behbahani, Saeed Amini, Mohammad Reza Khosrojerdi
Abstract: The machinability of Al 6061 in 1D and 2D ultrasonic assisted turning (UAT) in terms of machining forces, surface roughness and hardness is investigated in this research. In order to perform the machining experiments, a 1D vibration tool and a 2D vibration tool are designed and manufactured. The cutting forces and surface roughness of the work-pieces in 1D UAT and 2D UAT are measured in different cutting speeds and feed rates and compared with that in conventional machining. To investigate the effect of the ultrasonic vibration on the material properties, hardness tests are performed on the work-piece material and micro-hardness tests are carried out on the chip specimens. The results showed that reduction in the cutting forces occurred in UAT. The results also showed that the surface roughness is exceled in UAT in comparison with the conventional machining. While no detectable effect of the ultrasonic vibration on the work-piece material could be observed, the chip micro-hardness experiments showed that the softening phenomenon occurred in UAT, which can be the cause of the force reduction in UAT.
Authors: A.A. Ibrahim
Abstract: Roller burnishing process was applied to Al2O3/A356 composite specimens. The process was carried out on vertical milling machine. Effects of the burnishing process with varying process parameters on the characteristics of the machined surface and sub-surfaces were investigated. Residual stress distribution at different depths beneath the burnished surfaces, microhardness distribution, surface roughness were used as criteria to obtain the optimum burnishing conditions that give burnished surfaces with high integrity for the Al2O3/A356 composite. Results showed an improvement in surface characteristics of Al2O3/A356 composites using burnishing process. The better surface roughness was obtained with double passes burnishing, depth of penetration of 0.12 mm, and burnishing speed of 72 mm/min. Increase of number of burnishing passes increases the value of residual compressive stress and the microhardness at the burnished surface and subsurface. The microhardness slightly decreased with the increase of burnishing speed.
Authors: Ting Zhang, Xing Sheng Tong
Abstract: In this study, low temperature plasma carburizing of austenitic stainless steels has been studied, with the aim to improve the hardness and wear resistance of austenite layers. Austenitic stainless steels were plasma carburized at 450°C, using C3H8 as carbon carrier gas. Depth profiles of hardness, hardness distribution and the friction coefficient of carburized layer were measured. The results show that carburized layers range from 10 to 20μm, causing the improvement of the hardness and wear resistance of the surface of austenitic stainless steels.
Authors: Jostein Røyset, Hilde Hovland, Nils Ryum
Authors: Hamed Razavi, Mohammad Javad Nategh, H. Soleimanimehr
Abstract: The experimental investigation of UAT shows that the movement of cutting tool edge relative to the workpiece results from the cutting speed, feed speed and tools vibration in tangential direction affects the lateral machined surface of workpiece and leaves a repeating pattern of toothed regions on it. In UAT process, because of constant feed rate of tool toward workpiece, the cutting tool never separates from workpiece, though the tool rake face may separate periodically from chip in every cycle of vibration. This results in an increase in the surface hardness of the lateral machined surface in comparison with conventional turning (CT). The results of the present study confirm the advantage of UAT as far as the lower cutting force is concerned compared with CT. The higher surface hardness of the lateral surface observed in UAT causes the maximum cutting force to increase but the average force decreases with respect to CT.
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