Grain Refinement of Pure Magnesium Using Nonlinear Twist Extrusion

2018 ◽  
Vol 939 ◽  
pp. 54-62 ◽  
Author(s):  
Muhammad Lutfi Maulidi ◽  
Hiroyuki Miyamoto ◽  
Motohiro Yuasa
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Bulk Material ◽  
Equivalent Plastic Strain ◽  
Pure Magnesium ◽  
Electron Backscattered Diffraction ◽  
Twist Extrusion ◽  
First Pass ◽  
Different Temperatures ◽  
Number Of Passes

Nonlinear Twist Extrusion (NTE) is a new severe plastic developed (SPD) method for producing grain refinement by extruding and twisting bulk materials through the channel designed for more effective straining compared with the so-called twist extrusion (TE). In this experiment pure magnesium was pressed using NTE for up to 4 passes. The pressing was conducted under two different temperatures, the first pass was conducted in 523K followed by pressing from 2 to 4 passes at 473K pressing temperature. The microstructure of the material is observed with increasing number of passes using optical microscopy (OM), laser microscope and scanning electron microscopy (SEM) electron backscattered diffraction (EBSD). Grain size decreased with increasing passes and become finer than those obtained by other SPD processing. If compared by the same equivalent plastic strain, and it suggests that NTE is a promising approach in strengthening bulk material. The grain size of the as-received material reduced from 97μm down to 3μm after 4 passes. Moreover, the hardness of material also increasing up to 41Hv for the first pass and constantly increased with the increasing number of pressing. This result shows that NTE is one of the promising methods in severe plastic deformation.

scholarly journals Crystallography of grain refinement in cast zinc–copper alloys

2015 ◽  
Vol 48 (3) ◽  
pp. 890-900 ◽  
Author(s):  
Zhilin Liu ◽  
Dong Qiu ◽  
Feng Wang ◽  
John A. Taylor ◽  
Mingxing Zhang
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Copper Alloys ◽  
Diffraction Method ◽  
Electron Backscattered Diffraction ◽  
Grain Coarsening ◽  
Cu Content ◽  
Edge Matching ◽  
Average Grain Size ◽  
Cast Alloys

Adding the peritectic forming element Cu effectively reduced the average grain size of cast Zn by over 85%. At a specified cast condition, the smallest grain size was obtained at 2 wt% Cu addition. A further increase in Cu content led to grain coarsening in the cast Zn–Cu alloys. Although the solute effect of Cu was predominately responsible for the grain refinement through restriction of the grain growth, it was found that the variation of grain size is also closely related to the formation of the pro-peritectic phase, ∊-CuZn4. Crystallographic calculations using the edge-to-edge matching model showed low interatomic misfit and interplanar mismatch between Zn and the ∊-CuZn4phase. In addition, a reproducible h.c.p.–h.c.p. (h.c.p. denotes hexagonal close-packed) orientation relationship between Zn and the ∊-CuZn4particles (located within the Zn grain centres) was also experimentally determined using the electron backscattered diffraction method. This indicated the high potency of the pro-peritectic ∊-CuZn4particles as effective heterogeneous nucleation sites for η-Zn, which further refined the Zn grains. However, when the Cu content was over 2.0 wt%, formation of large ∊-CuZn4particles resulted in grain coarsening of the cast alloys.

scholarly journals The Effect of ECAP Temperature on the Microstructure and Properties of a Rolled Rare Earth Magnesium Alloy

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1554 ◽  
Author(s):  
Yun Tan ◽  
Wei Li ◽  
Weiwei Hu ◽  
Xiaofang Shi ◽  
Liang Tian
Keyword(s):  
Grain Size ◽  
Rare Earth ◽  
Magnesium Alloy ◽  
Deformation Temperature ◽  
Diffraction Intensity ◽  
Electron Backscattered Diffraction ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Different Temperatures ◽  
Microstructure Examination

Deformation of an as-rolled rare earth Mg-2Y-0.6Nd-0.6Zr alloy, at different temperatures, was carried out along the BC (90° anticlockwise rotation of the samples after each ECAP pass) route by equal channel angular pressing (ECAP). The effects of the deformation temperature and the predeformation on the microstructure of the magnesium alloy were determined by the microstructure examination. The slip systems and texture change of the Mg-2Y-0.6Nd-0.6Zr alloy were investigated by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD), after equal channel angular deformation. The results showed that after seven passes of rolling, the grain size in the Mg-2Y-0.6Nd-0.6Zr alloy was refined to approximately 22 µm and the slip occurred mainly by a cylindrical slip and a pyramidal slip. After one pass of ECAP at 340 °C, the internal average grain size was significantly reduced to 11 µm, the cylindrical diffraction intensity clearly weakened, and the pyramidal diffraction intensity increased. EBSD pole figure analysis revealed that the base texture of the rolled Mg-2Y-0.6Nd-0.6Zr alloy weakened from 24.31 to 11.34 after ECAP. The mechanical properties indicated that the tensile strength and elongation of the rolled Mg-2Y-0.6Nd-0.6Zr alloy reached maximum values, when the deformation temperature was 340 °C.

scholarly journals THE EFFECT OF ECAP PROCESSING TO HARDNESS, SURFACE MORPHOLOGI, AND CORROSION RESISTANCE OF 6061 ALUMINIUM ALLOYS

Metalurgi ◽  
2021 ◽  
Vol 36 (2) ◽  
Author(s):  
Vinda Puspasari ◽  
I. Nyoman Gede P. A. ◽  
Efendi Mabruri ◽  
Satrio Herbirowo ◽  
Edy Priyanto Utomo
Keyword(s):  
Grain Size ◽  
Corrosion Resistance ◽  
Corrosion Behaviour ◽  
Bulk Material ◽  
Ecap Processing ◽  
Al 6061 ◽  
Fine Grain ◽  
Ecap Process ◽  
Mechanical And Physical Properties ◽  
Number Of Passes

Al-Mg-Si alloys (6xxx) has been widely used as structural materials in building and vehicles because of its excellent strength and corrosion resistance. The improvement of fine grain microstructure which can increase mechanical and physical properties become an interesting field in recent research.. Equal channel angular press is the most promising method to apply severe plastic deformation (SPD) which can produce ultra-fine grain in the bulk material without residual porosity. This study presents some experiments results on the effect of ECAP number of passes variation to the hardness, microstructure, and corrosion behaviour of Al 6061 alloys. The samples were annealed in the furnace with argon gas environment at 530°C for 4 hours and then immersed in liquid nitrogen for 5 minutes before ECAP process. The ECAP process was done with Bc route using dies with 120° of internal channel angle and pass variation of 1, 2, 3, and 4. The optimum hardness is 107.58 HRB in Al 6061 samples with 3 passes of ECAP. The increasing ECAP number of passes leads to a significant grain size reduction from 0 way pass, the grain size is around 10 µm, while for a 4 way pass, the grain size is around 2.5 µm. The corrosion resistance of Al 6061 alloys increased with the increasing number of passes in ECAP process.

Effect of Processing on Grain Size and Corrosion of AA2024-T3

CORROSION ◽  
2011 ◽  
Vol 67 (10) ◽  
pp. 105001-105001-10 ◽  
Author(s):  
K.D. Ralston ◽  
J.G. Brunner ◽  
S. Virtanen ◽  
N. Birbilis
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Polarization Current ◽  
Electron Backscattered Diffraction ◽  
Microstructural Refinement ◽  
Transmission Electron ◽  
Material Environment ◽  
Deformation Processes ◽  
Specific Material ◽  
Ph Range

Abstract Recent works on high-purity materials have indicated that microstructural modification via grain refinement can alternately reduce or enhance corrosion, depending on the specific material-environment combination. Generally, however, a paucity of information exists in understanding how microstructural alteration and processing, in combination with grain refinement, affects corrosion. In this work, the effect of microstructural refinement on an alloy containing a high number density of precipitates and intermetallics is explored. Grain-refined AA2024-T3 (UNS A92024) samples were produced through severe plastic deformation processes and their corrosion response was compared to control samples of commercial ingot and sheet across the pH range. Microstructure and grain size were characterized using a combination of electron backscattered diffraction and transmission electron microscopy. It is revealed that there is a difference in corrosion between the specimens (which possess nearly the same bulk chemistry) as based on anodic potentiodynamic polarization, current transient, and exposure/profilometry experiments in sodium chloride (NaCl) electrolytes. However, in all cases, the effect is dominated by the environment, micro-chemical differences, and grain size.

Microstructure Development in Single and Double-Pass Friction Stir Processing of Aluminium

2013 ◽  
Vol 753 ◽  
pp. 50-53 ◽  
Author(s):  
Devinder Yadav ◽  
Ranjit Bauri
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Friction Stir Processing ◽  
Recrystallization Process ◽  
Pure Aluminium ◽  
Electron Backscattered Diffraction ◽  
Double Pass ◽  
Tem Analysis ◽  
Friction Stir ◽  
First Pass

Single pass and double-pass friction stir processing was carried out on commercially pure aluminium at a rotation speed of 640 rpm and traverse speed of 150 mm/min and a detailed electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) analysis was carried out to understand the microstructure developed. The grain size was refined substantially after the first pass whereas there was no significant change in the grain size after the second pass. This indicates that the final grain size after friction stir processing does not depend on the starting grain size. The equiaxed fine grains were formed by dynamic recrystallization process as revealed by EBSD analysis. TEM observations showed banded contrast across the grain boundaries indicating grain boundaries to be in equilibrium. Free dislocations observed inside grains after the first pass were well arranged into subgrain boundaries after the second pass. EBSD also revealed some variation in microstructural features such as grain size, texture index, grain orientation spread and grain average misorientation across the surface and also in the cross section of the stir zone both after single and double pass.

Ultra-Fine Ferrite Grain Refinement by Static Re-Crystallization of Hot Rolled Vanadium Micro-Alloyed Steels

2010 ◽  
Vol 442 ◽  
pp. 227-235
Author(s):  
E. Ahmad ◽  
T. Manzoor ◽  
M. Sarwar
Keyword(s):  
Grain Boundaries ◽  
Grain Refinement ◽  
Grain Growth ◽  
Microalloyed Steels ◽  
Ultrafine Grain ◽  
Electron Backscattered Diffraction ◽  
Effective Dispersion ◽  
Different Temperatures ◽  
Ebsd Technique ◽  
Hot Rolled

The phenomenon of ultrafine-grain refinement of ferrite during transformational grain refinement (TGR) followed by static re-crystallization of vanadium micro-alloyed steels was studied. A substantial grain refinement (2.8m) was attained during TGR process by rolling at 900°C. Cold rolling with 70% of reduction introduced strain, utilized for re-crystallization during annealing at different temperatures. Electron Backscattered Diffraction (EBSD) technique was employed to quantify the low angle grain boundaries (LAGB) and high angle grain boundaries (HAGB) spacings and results were correlated with hardness drops during annealing process. At higher annealing times and temperatures the vanadium precipitates restricted the process of grain growth probably due to effective dispersion strengthenening. The abnormal grain growth during annealing, predicted previously for niobium steels, found absent in the present vanadium microalloyed steels.

scholarly journals Research on Grain Refinement Mechanism of 6061 Aluminum Alloy Processed by Combined SPD Methods of ECAP and MAC

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1246 ◽  
Author(s):  
Zhenwei Zhang ◽  
Junli Wang ◽  
Qinglong Zhang ◽  
Supeng Zhang ◽  
Qingnan Shi ◽  
...  
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Grain Refinement ◽  
Short Form ◽  
Secondary Phase ◽  
Processing Route ◽  
Secondary Phases ◽  
Electron Backscattered Diffraction ◽  
6061 Aluminum Alloy ◽  
Average Grain Size

Equal channel angular pressing (ECAP) and multi-axial compression deformation (MAC) are severe plastic deformation (SPD) processes that produce bulk nanostructured materials with ultrafine grains. The grains could be observably refined by multi-pass of ECAP and MAC. This research proposed new routes of cyclic equal channel compression (CECC), which combines ECAP and MAC to increase the mechanical properties of 6061 aluminum alloy. The tests, which are conducted through electron backscattered diffraction (EBSD) and transmission electron microscope (TEM), were performed on the grain size, recrystallization distribution, misorientation distributions, dislocations, and secondary phase distributions of CECC-processed 6061 aluminum alloys on the purpose of exploring the mechanism of grain refinement. MEM is the short form for the CECC processing route of MAC + ECAP + MAC, which is one ECAP pass between two MAC passes. The tests results showed that the average grain size could reach to as much as 1.1 μm after two MEM deformation circles named MEM-MEM, with the non-annealing average grain size being 21 μm and recrystallization annealed average grain size being 28 μm. The dislocation cells, which could be transformed into sub-grains with the increase of the strain, were formed by the slip and the accumulation of dislocations. The secondary phase was Mg2Si, which could prevent the refined grains from growing up again by pinning at the grain boundaries. Above all, the dislocation proliferation and secondary phases will both lead to the grain refinement.

scholarly journals Effect of Vanadium Reinforcement on the Microstructure and Mechanical Properties of Magnesium Matrix Composites

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 806
Author(s):  
Liqing Sun ◽  
Shuai Sun ◽  
Haiping Zhou ◽  
Hongbin Zhang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Milling Process ◽  
Mg Alloy ◽  
Matrix Composites ◽  
Magnesium Matrix Composites ◽  
Pinning Effect ◽  
Average Grain Size ◽  
The Matrix ◽  
Hot Press Sintering

In this work, vanadium particles (VP) were utilized as a novel reinforcement of AZ31 magnesium (Mg) alloy. The nanocrystalline (NC) AZ31–VP composites were prepared via mechanical milling (MM) and vacuum hot-press sintering. During the milling process, the presence of VP contributed to the cold welding and fracture mechanism, resulting in the acceleration of the milling process. Additionally, increasing the VP content accelerated the grain refinement of the matrix during the milling process. After milling for 90 h, the average grain size of AZ31-X wt % Vp (X = 5, 7.5, 10) was refined to only about 23 nm, 19 nm and 16 nm, respectively. In the meantime, VP was refined to sub-micron scale and distributed uniformly in the matrix, exhibiting excellent interfacial bonding with the matrix. After the sintering process, the average grain size of AZ31-X wt % VP (X = 5, 7.5, 10) composites still remained at the NC scale, which was mainly caused by the pinning effect of VP. Besides that, the porosity of the sintered composites was no more than 7.8%, indicating a good densification effect. As a result, there was little difference between the theoretical and real density. Compared to as-cast AZ31 Mg alloy, the microhardness of sintered AZ31-X wt % VP (X = 5, 7.5, 10) composites increased by 65%, 87% and 96%, respectively, owing to the strengthening mechanisms of grain refinement strengthening, Orowan strengthening and load-bearing effects.

scholarly journals Switch Strategy from Direct Aspiration First Pass Technique to Solumbra Improves Technical Outcome in Endovascularly Treated Stroke

2021 ◽  
Vol 18 (5) ◽  
pp. 2670
Author(s):  
Enrico Pampana ◽  
Sebastiano Fabiano ◽  
Gianluca De Rubeis ◽  
Luca Bertaccini ◽  
Alessandro Stasolla ◽  
...  
Keyword(s):  
Added Value ◽  
Stroke Patients ◽  
First Line ◽  
Anterior Circulation ◽  
First Pass ◽  
Procedural Time ◽  
The Mean ◽  
The Difference ◽  
Number Of Passes ◽  
Switch Strategy

Background: The major endovascular mechanic thrombectomy (MT) techniques are: Stent-Retriever (SR), aspiration first pass technique (ADAPT) and Solumbra (Aspiration + SR), which are interchangeable (defined as switching strategy (SS)). The purpose of this study is to report the added value of switching from ADAPT to Solumbra in unsuccessful revascularization stroke patients. Methods: This is a retrospective, single center, pragmatic, cohort study. From December 2017 to November 2019, 935 consecutive patients were admitted to the Stroke Unit and 176/935 (18.8%) were eligible for MT. In 135/176 (76.7%) patients, ADAPT was used as the first-line strategy. SS was defined as the difference between first technique adopted and the final technique. Revascularization was evaluated with modified Thrombolysis In Cerebral Infarction (TICI) with success defined as mTICI ≥ 2b. Procedural time (PT) and time to reperfusion (TTR) were recorded. Results: Stroke involved: Anterior circulation in 121/135 (89.6%) patients and posterior circulation in 14/135 (10.4%) patients. ADAPT was the most common first-line technique vs. both SR and Solumbra (135/176 (76.7%) vs. 10/176 (5.7%) vs. 31/176 (17.6%), respectively). In 28/135 (20.7%) patients, the mTICI was ≤ 2a requiring switch to Solumbra. The vessel’s diameter positively predicted SS result (odd ratio (OR) 1.12, confidence of interval (CI) 95% 1.03–1.22; p = 0.006). The mean number of passes before SS was 2.0 ± 1.2. ADAPT to Solumbra improved successful revascularization by 13.3% (107/135 (79.3%) vs. 125/135 (92.6%)). PT was superior for SS comparing with ADAPT (71.1 min (CI 95% 53.2–109.0) vs. 40.0 min (CI 95% 35.0–45.2); p = 0.0004), although, TTR was similar (324.1 min (CI 95% 311.4–387.0) vs. 311.4 min (CI 95% 285.5–338.7); p = 0.23). Conclusion: Successful revascularization was improved by 13.3% after switching form ADAPT to Solumbra (final mTICI ≥ 2b was 92.6%). Vessel’s diameter positively predicted recourse to SS.

scholarly journals Microstructure Evaluation Study of Al5083 Alloy Using EBSD Technique after Processing with Different ECAP Processes and Temperatures

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 862
Author(s):  
Muneer Baig ◽  
Asiful H. Seikh ◽  
Ateekh Ur Rehman ◽  
Jabair A. Mohammed ◽  
Faraz Hussain Hashmi ◽  
...  
Keyword(s):  
Grain Refinement ◽  
Evaluation Study ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Microstructure Evaluation ◽  
Microstructural Evaluation ◽  
Higher Temperature ◽  
Ebsd Technique ◽  
Number Of Passes ◽  
Positive Effect

The temperature effects on the microstructural evolution of a coarse-grained Al5083 alloy during equal channel angular pressing (ECAP), were studied at ambient and high temperatures. The microstructural evaluation was done using an EBSD (electron backscattering diffraction) process. The grain refinement occurred as the number of passes increased, which had a positive effect on its strength. Additionally, increasing the pressing temperature leads to a decrease in the new grain’s formation and an increase in the normal grain size in the third pass. This can be ascribed to the unwinding of strain similarity between the grains because of the continuous activity of dynamic recuperation and the grain limit sliding occurring at a higher temperature. The attainment of grain refinement is examined exhaustively in this study.

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