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Synergistic effect of ball milling time and nano‑sized Y2O3 addition on hardening of Cu‑based nanocomposites

Salur Emin

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e103, 1--18

EN

A fruitful combination of powder metallurgy and the mechanical alloying route is one of the most promising process for producing advanced Cu-based nanocomposites. In this study, three different material systems, namely, pure copper (Cu), 5 wt% Cr reinforced Cu matrix composites, and 1 wt% Y2O3 reinforced Cu-Cr matrix nan-composites were synthesized by ball milling method at different milling times. The influence of different ball milling times (0.5, 2, and 4 h) and different types of reinforcements (Cr and Y2O3) on the powder and sintered parts properties were thoroughly analyzed with a holistic approach. The milled powders were then consolidated using a cold press followed by a liquid phase sintering process. Results revealed that the Cr and Y2O3 particles were fractionally dispersed and imbedded in the ductile Cu matrix with respect to increasing milling time. Milling for 4 h of Cu-Cr-2O3 powders produced the lowest level of particle size (28 μm) with reduced and flattened and uniformly distributed reinforcement phases due to intense plastic deformation induced shearing effect and dominant powder-ball-jar collisions. Besides, the ball milling process of the same powders concluded a decrement of crystallite size to 35 nm in concomitant with an increase of lattice strain and dislocation density ⁓ % 0.3 and 0.8×1015 line/m2 , respectively. Brinell hardness of the sample produced by these powders increased from 39 to 95 HB. A ⁓%145 striking increase of hardness could be attributed to the strong hindrance of high-dense dislocations triggered by several concurrent strengthening mechanisms. Nevertheless, relative density results of sintered samples revealed that the addition of Cr and Y2O3 along with increasing milling time deteriorated the density due to the higher hardness and brittleness of milled powders and accompanying worsened compressibility and sinterability. The source of noticed differences between hardness and density results were discussed within the process-structure-performance framework.

2

Properties Of MgB2/Ga Composites Prepared By Mechanical Alloying

Yoon K., Ahn J.-H.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1271--1274

EN

In this study, we examined the effect of Ga-doping and mechanical alloying in MgB2 on microstructural and phase evolution. A comparison was made between in-situ and ex-situ processed Mg-B-Ga samples. Densification was markedly improved by ex-situ sintering of ball-milled MgB2+Ga. The Ga-doping and ball-milling prior to sintering resulted in the formation of impurity phases such as MgO, Ga5Mg2 and Ga2O3. Lattice parameter of MgB2 increased with increasing ball-milling duration as well as by Ga-doping.

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Effect Of Heat-Treatment On Microstructure And Magnetic Properties Of Nanocrystallized Mn-Zn Ferrite Powders

Lee W. H., Hong C. S., Chang S. Y.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1347--1350

EN

The initial ferrite powders were subjected to high energy ball milling at 300rpm for 3h, and subsequently heat-treated at 573-1273K for 1h. Based on the observation of microstructure and measurement of magnetic properties, the heat-treatment effect was investigated. The size of initial powders was approximately 70μm. After milling, the powders with approximately 230nm in size were obtained, which were composed of the nano-sized particles of approximately 15nm in size. The milled powders became larger to approximately 550nm after heat-treatment at 973K. In addition, the size of particles increased to approximately 120nm with increasing temperature up to 973K. The coercivity of initial powders was almost unchanged after milling, whereas the saturation magnetization increased. As the heat-treatment temperature increased, the saturation magnetization gradually increased and the maximum coercivity was obtained at 773K.

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Influence of workpiece inclination angle on the surface roughness in ball end milling of the titanium alloy Ti-6Al-4V

Daymi A., Boujelbene M., Linares J. M., Bayraktar E., Ben Amara A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 35, nr 1

79-86

EN

Purpose: The aim of this work is to provide an in-depth understanding of the surface texture produced by various workpiece inclination angles using high speed finish ball end-milling of the titanium alloy Ti-6Al-4V. Design/methodology/approach: This paper presents an approach to develop a mathematical model of surface roughness in end-milling by the experimental design methodology. Machining variables such as cutting speed, feed and radial depth of cut, which are easily controllable, are considered in building the model. The influence of the workpiece inclination angle on the surface roughness of the machined workpiece was also investigated. Findings: According to the mathematical model, an increase in either the feed or the radial depth of cut increases the surface roughness, whilst an increase in cutting speed decreases it. The radial depth of cut ae is the most significant parameter in the model. Results analysis of the 2D/3D surface roughness parameters of the machined parts shows the improvement of the surface roughness quality when it is machined with a workpiece inclination angle of 25°. Research limitations/implications: As perspectives of this work, we can study the influence of the different machining strategies on the surface integrity of this titanium alloy, including the study of the residual stress. Practical implications: We propose to study the improvement of the surface quality of the orthopedic prostheses, which is an influencing parameter in their lifetime, by implementing the high speed cutting technique. The mathematical model of the surface roughness is a very important result of this work. In fact, it allows selecting the best cutting conditions to obtain a better workpiece surface quality. Originality/value: In this work, three dimensional surface roughness parameters were studied: the 3D surface topographies were obtained using a 3D measurement station and the mathematical model of Sa. The arithmetic mean deviation of the surface was established in order to minimize the experimental works and to have an idea about the surface roughness evolution as a function of cutting parameters.