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RISS 인기검색어
- 검색키워드
- 저자 : Hamidreza Mohammadian Semnani (검색결과 3 건)
- 무료
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Computational and Experimental Studies on the Effect Back Pressure on Twist Extrusion Process
Mehran Nouri,Hamidreza Mohammadian Semnani,Esmaeil Emadoddin 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8
In the current study, aluminium 6063 alloy (AA6063) was successfully gain refined by twist extrusion (TE) technique. TEis a representative severe plastic deformation process to fabricate ultrafine-grained in bulk materials by repetitive passes. In order to investigate the influence of back pressure, a direct extrusion (DE) channel was embedded after the twist zoneand the behavior of AA6063 was investigated and compared with and without this channel. Analyzing microstructuralevolutions by scanning electron microscope and Vickers microhardness evaluations showed that, adding the DE channelincreased the hardness distribution and a more homogenous structure was obtained. Finite element analysis was utilized tostudy the distribution of the equivalent plastic strain (PEEQ) numerically. According to the obtained results, with applyingthe TE process, strain increase was observed all over the sample surface, whereas modeling the DE channel after the twistzone caused a better homogeneity in the PEEQ distribution of the transverse cross-section. The PEEQ distribution duringTE process can be correlated to the extent of grain refinement and the uniformity of ultrafine grains. This method seems tobe very interesting and very promising for the future industrial application.
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Nouri, Mehran,Mohammadian Semnani, Hamidreza,Emadoddin, Esmaeil,Seop Kim, Hyoung Elsevier 2018 MEASUREMENT -LONDON- Vol.127 No.-
<P><B>Abstract</B></P> <P>Twist extrusion (TE) is a relatively new severe plastic deformation technique in which radial deformation is heterogeneously distributed in the sample. In this research, in order to achieve favorable properties, a direct extrusion (DE) channel was embedded after the twist zone at the bottom of the TE die. The plastic deformation behavior of aluminum alloy 6063 (AA6063) was investigated in the TE process, with and without the DE channel. AA6063 successfully underwent TE under the conditions designed using the finite element analysis. According to the simulation results, a very heterogeneous distribution of the equivalent plastic strain (PEEQ) was observed in TE, while the TE+DE simulation exhibited more homogeneous PEEQ in the central and lateral regions. Microstructural evolution analysis using scanning electron microscope and Vickers microhardness evaluations showed that utilizing the DE channel increased the hardness and provided a more homogenous microstructure. Moreover, tensile testing results indicated an increase in strength and enhanced mechanical properties of the TE+DE processed AA6063.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Innovative twist extrusion was achieved by embedding a direct extrusion channel after the twist zone. </LI> <LI> Finite element analysis showed that the direct extrusion channel decreased sample deformation heterogeneity. </LI> <LI> All data indicated that absence of sufficient back pressure led to distortion and elongation of samples. </LI> <LI> The best microstructure was achieved by combining twist extrusion and direct extrusion channel. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Mojtaba Dehghan,Fathallah Qods,Mahdi Gerdooei,Hamidreza Mohammadian‑Semnani 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12
In this study, the cross accumulative roll-bonding (CARB) process, as an improved technique of the conventional accumulativeroll-bonding (ARB), was conducted on the AA1050 sheet up to 10 passes in two processing modes. The specimenswere either preheated before the rolling step of CARB passes and promptly roll bonded (warm CARB) or were processedat room temperature (cold CARB). The microstructure of samples was characterized using a scanning electron microscope. The effect of intermediate heat treatment on the planar homogeneity of the mechanical properties in the CARB (and evenARB) deformed sheets has not been examined yet. Hence, the present research focuses on the comparison of the planarisotropy of tensile properties between warm and cold CARB products. Also, the uniformity of microhardness distributionthroughout the thickness of samples was evaluated. The warm CARB presented higher elongation, lower tensile strength andmicrohardness with more uniformity of the microhardness distribution, and also premier planar isotropy of the mechanicalproperties than the cold CARB.
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