scholarly journals Effective Surface Nano-Crystallization of Ni2FeCoMo0.5V0.2 Medium Entropy Alloy by Rotationally Accelerated Shot Peening (RASP)

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1074 ◽  
Author(s):  
Ningning Liang ◽  
Xiang Wang ◽  
Yang Cao ◽  
Yusheng Li ◽  
Yuntian Zhu ◽  
...  
Keyword(s):  
Grain Size ◽  
Surface Layer ◽  
Grain Refinement ◽  
Shot Peening ◽  
Model Material ◽  
High Entropy Alloy ◽  
Transmission Electron Microscopy Analysis ◽  
High Entropy ◽  
Average Grain Size ◽  
Electron Microscopy Analysis

The surface nano-crystallization of Ni2FeCoMo0.5V0.2 medium-entropy alloy was realized by rotationally accelerated shot peening (RASP). The average grain size at the surface layer is ~37 nm, and the nano-grained layer is as thin as ~20 μm. Transmission electron microscopy analysis revealed that deformation twinning and dislocation activities are responsible for the effective grain refinement of the high-entropy alloy. In order to reveal the effectiveness of surface nano-crystallization on the Ni2FeCoMo0.5V0.2 medium-entropy alloy, a common model material, Ni, is used as a reference. Under the same shot peening condition, the surface layer of Ni could only be refined to an average grain size of ~234 nm. An ultrafine grained surface layer is less effective in absorbing strain energy than a nano-grain layer. Thus, grain refinement could be realized at a depth up to 70 μm in the Ni sample.

Fabrication and Characterization of Nanostructured Surface Layer of 38CrSi Steel

2007 ◽  
Author(s):  
Shi-Ning Ma ◽  
De-Ma Ba ◽  
Chang-Qing Li ◽  
Fan-Jun Meng
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Surface Layer ◽  
Grain Refinement ◽  
Fine Particles ◽  
Nanostructured Surface ◽  
Cell Structures ◽  
Strain And Strain Rate ◽  
Transmission Electron ◽  
Average Grain Size

A nanocrystalline surface layer was fabricated on a 38CrSi Steel with tempered sorbite structure by using Supersonic Fine Particles Bombarding (SFPB). The microstructural evolution of SFPB-treated specimens under different processing conditions was characterized by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Experimental evidence showed severe plastic deformation and obvious grains refinement were observed and a nanocrystalline surface layer (grain size < 100nm) was found after SFPB treatment. The thickness of nanostructured surface layer varies from a few to about 25μm as treated time increasing from 80s to 240s, but the grain size varies slightly. For the sample treated for 240s, the average grain size of equiaxed nanocrystallites with random crystallographic orientations on the top surface layer is about 16nm. The indexing of diffraction rings indicates nanostructured surface layer consists of ferrite and cementite phases without any evidence of a new phase. The structure size increases gradually from nano-scale to original-scale with an increase of the distance from the top surface layer. In the region about 20–30μm deep from the top surface, the microstructures are mainly composed of 60–100nm roughly equiaxed grains and subgrains. Some subbounsaries are composed of dense dislocation walls (DDWs). In this regime some cell structures are also seen, which are separated by dislocation lines (DTs) and some DDWs. Experimental analysis indicate coarse-grains are gradually refined into nano-sized grains by dislocations activity with gradual increase of strain and strain rate from matrix to treated surface. Both ferrite and cementite phases occur grain refinement. Grain refinement of 38CrSi sample is mainly attributed to the movement of dislocation.

scholarly journals Atomic Simulations of Grain Structures and Deformation Behaviors in Nanocrystalline CoCrFeNiMn High-Entropy Alloy

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1010 ◽  
Author(s):  
Junling Hou ◽  
Qiang Li ◽  
Chuanbao Wu ◽  
Limei Zheng
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Shape Change ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
Common Neighbor ◽  
High Entropy ◽  
Average Grain Size ◽  
The Face ◽  
Deformation Behaviors

Using the molecular dynamics method, the melting character, mechanical properties, microstructures, and strain deformation mechanisms of nanocrystalline CoCrFeNiMn high-entropy alloy are systematically investigated in the present work. The simulation results suggest that the melting point in CoCrFeNiMn high-entropy alloy decreases with the grain size, decreasing from 3.6 to 2.0 nm. The grain size has a significant effect on shear and Young’s modulus compared to bulk modulus. The stress-strain simulation demonstrates that the ultimate tensile strength decreases with the decrease of the grain size, while the plastic deformation increases with the decrease in grain size. While the average grain size decreases to 2.0 nm, the amorphization induced by small grain size reduces plastic deformation. The common neighbor analysis shows that the face-centered cubic (FCC) composition of CoCrFeNiMn decreases gradually with decreasing grain size. For the sample with a grain size of 2.0 nm, the FCC composition is about 19% at a strain of 20%, accompanied by severe amorphization. The inverse Hall-Petch effect is observed for nanocrystalline CoCrFeNiMn high-entropy alloy in the present simulations. The atomic snapshot of CoCrFeNiMn with a grain size of 2.0 nm under the uniaxial strain confirms that the grain shape change, stacking fault formation, and amorphization are important mechanisms of plastic deformation in nanocrystalline high-entropy CoCrFeNiMn.

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.

Modeling and Numerical Simulation Research on Hollow Steel Ingot Forging Process of Heavy Cylinder Forging

2013 ◽  
Vol 712-715 ◽  
pp. 627-632
Author(s):  
Min Liu ◽  
Qing Xian Ma
Keyword(s):  
Numerical Simulation ◽  
Grain Size ◽  
Shear Zone ◽  
Grain Refinement ◽  
Steel Ingot ◽  
Effective Strain ◽  
Meridian Plane ◽  
Forging Process ◽  
Forming Load ◽  
Average Grain Size

Aiming at the disadvantages of low utilization ratio of steel ingot, uneven microstructure properties and long production period in the solid steel ingot forging process of heavy cylinder forgings such as reactor pressure vessel, a new shortened process using hollow steel ingot was proposed. By means of modeling of lead sample and DEFORM-3D numerical simulation, the deformation law and grain refinement behavior for 162 ton hollow steel ingot upsetting at different reduction ratios, pressing speeds and friction factors were investigated, and the formation rule of inner-wall defects in upsetting of hollow steel ingots with different shape factors was further analyzed. Simulation results show that the severest deformation occurs in the shear zone of meridian plane in the upsetting process of hollow steel ingot, and the average grain size in the shear zone is the smallest. As pressing speed increases, the forming load gradually increases and the deformation uniformity gets worse, while the average grain size decreases. An increase in friction factor can increase the peak value of effective strain, but it significantly reduces the deformation uniformity, increases the forming load and goes against grain refinement. Moreover, the four kinds of defects on the inner wall of steel ingot can be eliminated effectively by referring to the plotted defect control curve for hollow steel ingot during high temperature upsetting.

scholarly journals Grain Refinement of a Powder Nickel-Base Superalloy Using Hot Deformation and Slow-Cooling

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1978 ◽  
Author(s):  
Xianqiang Fan ◽  
Zhipeng Guo ◽  
Xiaofeng Wang ◽  
Jie Yang ◽  
Jinwen Zou
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Hot Deformation ◽  
Nickel Base Superalloy ◽  
Polycrystalline Nickel ◽  
Slow Cooling ◽  
Homogeneous Microstructure ◽  
Average Grain Size ◽  
Nickel Base ◽  
Base Superalloy

A pre-hot-deformation process was applied for a polycrystalline nickel-base superalloy to active deformation twins and dislocations, and subsequent slow cooling treatment was used to achieve grain refinement and microstructure homogenization. The microstructural evolution of the alloy was investigated, and the corresponding underlying mechanism was discussed. It was found that twinning mainly occurred in large grains during pre-hot-deformation owing to the stress concentration surrounding the large grains. High density dislocations were found in large grains, and the dislocation density increased approaching the grain boundary. The average grain size was refined from 30 μm to 13 μm after slow cooling with a standard deviation of grain size decreasing from 10.8 to 2.8, indicating a homogeneous microstructure. The grain refinement and microstructure homogenization during cooling process could be achieved via (i) static recrystallization (SRX), (ii) interaction of twin tips and γ’ precipitates, and (iii) grain coarsening hindered by γ’ precipitates in grain boundaries.

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 Author Correction: Effect of FeCoNiCrCu0.5 High-entropy-alloy Substrate on Sn Grain Size in Sn-3.0Ag-0.5Cu Solder

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yu-An Shen ◽  
Chun-Ming Lin ◽  
Jiahui Li ◽  
Siliang He ◽  
Hiroshi Nishikawa
Keyword(s):  
Grain Size ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Alloy Substrate ◽  
Correction Effect

Transition of twinning behavior in CoCrFeMnNi high entropy alloy with grain refinement

2018 ◽  
Vol 712 ◽  
pp. 603-607 ◽  
Author(s):  
S.J. Sun ◽  
Y.Z. Tian ◽  
H.R. Lin ◽  
H.J. Yang ◽  
X.G. Dong ◽  
...  
Keyword(s):  
Grain Refinement ◽  
High Entropy Alloy ◽  
High Entropy

Effect of Surface Nano-Crystallization on Microstructure and Mechanic Properties of Commercial Pure Titanium

2004 ◽  
Vol 261-263 ◽  
pp. 1605-1610 ◽  
Author(s):  
Ai Ling Wen ◽  
R.M. Ren ◽  
Sheng Wu Wang ◽  
Shinichi Nishida
Keyword(s):  
Grain Size ◽  
Surface Layer ◽  
Shot Peening ◽  
Pure Titanium ◽  
High Energy ◽  
X Ray Diffraction ◽  
Surface Microhardness ◽  
Commercial Pure Titanium ◽  
Nano Crystalline ◽  
Crystalline Surface

The paper investigated nano-crystallization on surface layer of commercial pure titanium by using high-energy shot peening. The grain size and the microstructure in deformed surface layer by high-energy shot peening are analyzed with X-ray diffraction and TEM etc. In addition, the variations of surface microhardness are examined after high-energy shot peening. The results described that the nano-crystalline surface layer have been formed in commercial pure titanium with a structure of hexagonal closet packet, by high-energy shot peening. The surface microhardness increases and the grain size in nano-crystalline surface layer diminishes, with increasing the time in high-energy shot peening. The minimum nano-crystalline grain size is approximately 40 nm.

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