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Online since: January 2016
Authors: Rafael Sukhorukov, Farid Z. Utyashev, Radik Mulyukov, Vener Valitov
The methods of local form-shaping of the parts under SP [5] conditions allow to solve the problem of fabrication of the complicated axisymmetric parts provided a minimum metal loss, without application of powerful press equipment and massive forging tools and with minimum number of operations.
In this case the main mechanism of deformation is grain boundary sliding.
Therefore, in the rim of the disk it is important to have coarse-grained structure that give the material heat-resistance, and in the hub it is important to have fine-grained structure that provides higher strength.
It is characterized by a combination elongated in the radial direction coarse grains separated by thin layers of fine grains; this structure is typical for thermal deformation.
The experiments on generating disc regulated structure and its properties are described sufficiently detailed in a number of papers [1, 11].
In this case the main mechanism of deformation is grain boundary sliding.
Therefore, in the rim of the disk it is important to have coarse-grained structure that give the material heat-resistance, and in the hub it is important to have fine-grained structure that provides higher strength.
It is characterized by a combination elongated in the radial direction coarse grains separated by thin layers of fine grains; this structure is typical for thermal deformation.
The experiments on generating disc regulated structure and its properties are described sufficiently detailed in a number of papers [1, 11].
Online since: September 2005
Authors: Leo A.I. Kestens, Petra Backx
The occurrence of DRX is revealed by optical micrographs that
display bulging grain boundaries and the formation of newly formed grains.
As DRX leads to grain refinement and grain refinement leads to an increased strength, DRX is an appropriate instrument to improve the strength of this alloy.
At low strains twins are formed (1) and grain boundaries start bulging (2) but no new grains are formed yet.
Examples of such grains, are indicated with a question mark, cf.
It should be mentioned, however, that by not removing the doubtful grains we probably overestimate the number of orientations of which the crystal c-axis is parallel to the compression axis.
As DRX leads to grain refinement and grain refinement leads to an increased strength, DRX is an appropriate instrument to improve the strength of this alloy.
At low strains twins are formed (1) and grain boundaries start bulging (2) but no new grains are formed yet.
Examples of such grains, are indicated with a question mark, cf.
It should be mentioned, however, that by not removing the doubtful grains we probably overestimate the number of orientations of which the crystal c-axis is parallel to the compression axis.
Online since: December 2011
Authors: A.K. Mukhopadhyay, S. Raveendra, A. Kumar, K.S. Prasad, Indradev Samajdar
It is noteworthy that the number density of the dispersoids significantly increases with strain.
Figs. 2(a) through (d) represent transmission electron micrographs showing the evolution of recrystallized grain structure during SPD.
During the early stages of SPD, large, highly misoriented subgrains developed by local migration of boundaries [marked by arrows in Fig. 2(a)] and merger of suitably oriented subgrains leading to recrystallized grains [one such grain is labeled at the centre of Fig.2(b)].
Such processes, however, became increasingly restricted because of the formation of an increasing number density of dispersoids with strain.
With increasing strain, both the number density of the dispersoids and the percentage recrystallization increased.
Figs. 2(a) through (d) represent transmission electron micrographs showing the evolution of recrystallized grain structure during SPD.
During the early stages of SPD, large, highly misoriented subgrains developed by local migration of boundaries [marked by arrows in Fig. 2(a)] and merger of suitably oriented subgrains leading to recrystallized grains [one such grain is labeled at the centre of Fig.2(b)].
Such processes, however, became increasingly restricted because of the formation of an increasing number density of dispersoids with strain.
With increasing strain, both the number density of the dispersoids and the percentage recrystallization increased.
Online since: April 2020
Authors: Dong Sheng Wang
Due to toughening effect of residual nanoparticles in the remelting region of laser remelted nanostructured coating, grain-boundary strength is high and there are a considerable number of transgranular fractures, but the fractures in the remelting region of laser remelted conventional coating are basically intergranular fractures.
For ceramic materials, fracture mode of crystal grains is usually related to grain boundary strength.
As transgranular fractures need a large energy, grain boundary strength becomes greater, where crystal grains can easily go through transgranular fracture; on the contrary, the smaller the grain boundary strength, the more easily the crystal grains can experience intergranular fracture.
%Y2O3 nanopowder consists of nanoparticles with small grain sizes.
(3) Due to toughening effect of residual nanoparticles in the remelting region of laser remelted nanostructured coating, grain-boundary strength is high and there are a considerable number of transgranular fractures, but the fractures in the remelting region of laser remelted conventional coating are basically intergranular fractures
For ceramic materials, fracture mode of crystal grains is usually related to grain boundary strength.
As transgranular fractures need a large energy, grain boundary strength becomes greater, where crystal grains can easily go through transgranular fracture; on the contrary, the smaller the grain boundary strength, the more easily the crystal grains can experience intergranular fracture.
%Y2O3 nanopowder consists of nanoparticles with small grain sizes.
(3) Due to toughening effect of residual nanoparticles in the remelting region of laser remelted nanostructured coating, grain-boundary strength is high and there are a considerable number of transgranular fractures, but the fractures in the remelting region of laser remelted conventional coating are basically intergranular fractures
Online since: July 2013
Authors: Mark White, Yun Wang, Douglas Watson, Zhong Yun Fan, Shouxun Ji
Although a number of additions can be used to enhance the ductility, titanium is the most promising addition because of its wide application in wrought alloys.
The main influence of the titanium addition was in the reduction of the number of defects.
%Ti, the number and the size of the defects were reduced, as shown in Fig. 2b.
The grain size at the edge was smaller than that in the centre for the castings of all compositions.
Effect of Ti on the grain size of the Al-Mg-Si alloy solidified in the TP-1 mould.
The main influence of the titanium addition was in the reduction of the number of defects.
%Ti, the number and the size of the defects were reduced, as shown in Fig. 2b.
The grain size at the edge was smaller than that in the centre for the castings of all compositions.
Effect of Ti on the grain size of the Al-Mg-Si alloy solidified in the TP-1 mould.
Online since: September 2016
Authors: D.S. Balaji, C. Guhan, Thangasamy Jeyapoovan
The microhardness of the material at the surface is high compared to the core of the material, this is due to grain refinement the large elongated grains are refined into small grains on the surface layer after peening.
OA is a matrix of numbers arranged in rows and columns.
Before peening has the grain size of 2.8µm after peening has the grain size of 2.5µm.
Continuous striking of the sample surface with ball leads to larger grains are elongated into the smaller grains.
Based on this operation the best optimized result comes, when the Speed is 200 rpm, Diameter of ball is 10mm, and the number of balls are 100.
OA is a matrix of numbers arranged in rows and columns.
Before peening has the grain size of 2.8µm after peening has the grain size of 2.5µm.
Continuous striking of the sample surface with ball leads to larger grains are elongated into the smaller grains.
Based on this operation the best optimized result comes, when the Speed is 200 rpm, Diameter of ball is 10mm, and the number of balls are 100.
Online since: February 2006
Authors: Z. Horita, Yu Can Fu, Bing Xiao, Hong Jun Xu, Jiu Hua Xu, Hong Hua Su
Machining Performance of Brazed Diamond Wire Saw
with Optimum Grain Distribution
B.
Because brazing can only improve the bonding strength and the high protrusion of grains, the three-dimensional distribution of grains at the tool surface has effective impact on the machining performance of tools.
So only by synthetically adopting brazing and optimum grain distribution, can the new generation monolayer tools ultimately make use of and bring into full play the intrinsic performance superiority and machining advantages of diamond grains.
Fig. 5 shows contrast feed speed versus accumulated cutting area for monolayer brazed diamond saw with optimum grain distribution and sintered one with random grain distribution under the condition of keeping the same load electric current and machining object.
Why the life and machining efficiency of monolayer brazed diamond wire saw with optimum grain distribution obviously outperform those of multi-layer sintered one with random grain distribution can be better understood if one observes diamond grits failing process during sawing shown in Fig. 6.
Because brazing can only improve the bonding strength and the high protrusion of grains, the three-dimensional distribution of grains at the tool surface has effective impact on the machining performance of tools.
So only by synthetically adopting brazing and optimum grain distribution, can the new generation monolayer tools ultimately make use of and bring into full play the intrinsic performance superiority and machining advantages of diamond grains.
Fig. 5 shows contrast feed speed versus accumulated cutting area for monolayer brazed diamond saw with optimum grain distribution and sintered one with random grain distribution under the condition of keeping the same load electric current and machining object.
Why the life and machining efficiency of monolayer brazed diamond wire saw with optimum grain distribution obviously outperform those of multi-layer sintered one with random grain distribution can be better understood if one observes diamond grits failing process during sawing shown in Fig. 6.
Online since: March 2013
Authors: Radomír Kužel, Miloš Janeček, Zdeněk Matěj
Significant dependence of thermal stability of fine ECAP microstructure on number of passes was found.
As a consequence, the samples with higher number of passes were less stable.
Anyway, the difference in stability of the samples deformed by different number of ECAP passes is clear also in the evolution of line broadening (e.g.
However, the problem is that for recrystallization of severely deformed copper a fast grain growth is typical when only a few grains begin to grow quickly while others remain small.
We are not able to estimate grain growth above the limit from the XRD line profile broadening.
As a consequence, the samples with higher number of passes were less stable.
Anyway, the difference in stability of the samples deformed by different number of ECAP passes is clear also in the evolution of line broadening (e.g.
However, the problem is that for recrystallization of severely deformed copper a fast grain growth is typical when only a few grains begin to grow quickly while others remain small.
We are not able to estimate grain growth above the limit from the XRD line profile broadening.
Online since: May 2019
Authors: Mikhail Georgievich Leontiev
The dependence of the strength characteristics on the grain size is well described by the law of Hall-Petch, according to which when the average grain size is reduced by 3...5 times there is an increase in the hardness of the material, with a further decrease in the average grain size by more than 10 times – an increase in plasticity.
The melt has a large number of different impurities and it is necessary that the modifier particles were the center of crystallization.
Numbering of steel samples (1...5) corresponds to numbering of modifier samples (1...5).
Evaluation of grain size was carried out according to GOST 5639.
In samples 1 and 3, the grain value corresponds to two points (the actual average grain diameter is 0.387...0.694 and 0.338..0.581 mm, respectively), in other samples grain corresponds to three points or more (the actual average grain diameter of the control sample – 2,325...3,168 mm) (figure 9)
The melt has a large number of different impurities and it is necessary that the modifier particles were the center of crystallization.
Numbering of steel samples (1...5) corresponds to numbering of modifier samples (1...5).
Evaluation of grain size was carried out according to GOST 5639.
In samples 1 and 3, the grain value corresponds to two points (the actual average grain diameter is 0.387...0.694 and 0.338..0.581 mm, respectively), in other samples grain corresponds to three points or more (the actual average grain diameter of the control sample – 2,325...3,168 mm) (figure 9)
Online since: March 2021
Authors: Andreas Weisheit, Markus Bambach, Irina Sizova, Waldemar Koch, Rebar Hama-Saleh, Frank Meiners, Michael Mathes, Johannes Henrich Schleifenbaum, Susanne Hemes
Primary investigations on the microstructure and mechanical properties of the material show results similar to conventional hot forged material, but reduce the number of processing steps and increase the material yield.
Grain boundary angles were defined as misorientations ≥ 5°
Determine triple points of alpha-alpha grain boundaries in MATLAB/MTEX.
Heat treatment above the beta-transus-temperature results in a transformation of the elongated prior beta grains into equiaxed grains, up to 5 mm in width (diameter).
Summary, Conclusions & Outlook In the present study, a hybrid manufacturing process chain, combining hot forging with powder laser metal deposition (powder LMD) is presented, to produce hybrid demonstrator parts and reduce the number of processing steps as well as the amount of machining necessary after manufacturing.
Grain boundary angles were defined as misorientations ≥ 5°
Determine triple points of alpha-alpha grain boundaries in MATLAB/MTEX.
Heat treatment above the beta-transus-temperature results in a transformation of the elongated prior beta grains into equiaxed grains, up to 5 mm in width (diameter).
Summary, Conclusions & Outlook In the present study, a hybrid manufacturing process chain, combining hot forging with powder laser metal deposition (powder LMD) is presented, to produce hybrid demonstrator parts and reduce the number of processing steps as well as the amount of machining necessary after manufacturing.