scholarly journals Microstructure analysis and crack nucleation in TWIP steel tube at expansive deformation

2021 ◽  
Author(s):  
ChunYuan Liu ◽  
Kaihong Song ◽  
Wei Wu ◽  
Ping Jiang ◽  
YanFei Jiang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Room Temperature ◽  
Twip Steel ◽  
Crack Nucleation ◽  
Steel Tube ◽  
Austenite Phase ◽  
Expansion Test ◽  
Integral Number ◽  
Pile Up ◽  
The Difference

Abstract The expansion test of twinning induced plastic (TWIP) steel tube was carried out at room temperature. Cracks appeared inside the tube edge when TWIP steel tube expands by 15.6%. The microstructure evolution, deformation mechanism and crack generation of TWIP steel after expansion were investigated by XDR OM TEM and EBSD. The results show that TWIP steel tube still austenite phase after expansion at room temperature; a great deal of dislocations are gathered around the grain boundaries and twin boundaries, the integral number of twins is high, and the mechanism of expansion deformation is the joint action of dislocations slip and deformation twins; Twins produce a large number of finer secondary or even multiple twins, intersecting each other; After expansion, the silk texture with direction of <111>∥X0 dominated by rotating brass texture {110}<111> is gradually produced through grain deformation and rotation; The proportion of small angle grain boundaries increased greatly; It is deduced that the criterion of crack nucleation is based on the difference between the dislocation pile-up energy (DPE) and the crack nucleation energy (CNE), and the expansion deformation process of TWIP steel satisfies the condition of crack nucleation.

scholarly journals The Internal Friction of Single Crystals, Bicrystals and Polycrystals of Pure Magnesium

2015 ◽  
Vol 60 (1) ◽  
pp. 371-375 ◽  
Author(s):  
W.B. Jiang ◽  
Q.P. Kong ◽  
L.B. Magalas ◽  
Q.F. Fang
Keyword(s):  
Activation Energy ◽  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Room Temperature ◽  
Internal Friction Peak ◽  
Self Diffusion ◽  
Boundary Relaxation ◽  
The Difference

Abstract The internal friction of magnesium single crystals, bicrystals and polycrystals has been studied between room temperature and 450°C. There is no internal friction peak in the single crystals, but a prominent relaxation peak appears at around 160°C in polycrystals. The activation energy of the peak is 1.0 eV, which is consistent with the grain boundary self-diffusion energy of Mg. Therefore, the peak in polycrystals can be attributed to grain boundary relaxation. For the three studied bicrystals, the grain boundary peak temperatures and activation energies are higher than that of polycrystals, while the peak heights are much lower. The difference between the internal friction peaks in bicrystals and polycrystals is possibly caused by the difference in the concentrations of segregated impurities in grain boundaries.

The study lithoidal fracture of steel at electric arc smelting 35HGSL

2019 ◽  
pp. 55-64
Author(s):  
M. L. Scriabin ◽  
A. I. Chuprakov
Keyword(s):  
Grain Boundaries ◽  
Electric Arc ◽  
Austenite Phase ◽  
Individual Particles

The paper deals with the classification of defects of castings obtained by electric arc smelting. Of particular interest to researchers is the rock-like and naphthalene fracture, but there is still no clear mechanism explaining its origin. A stone-like fracture is characterized by a clearly defined uniform surface over which the fracture occurs. Grain boundaries are partially soluble in the austenite phase, consisting of fine individual particles or films formed from molten eutectics. It is also worth noting that in most cases, the stone-like fracture is observed at the grain boundaries.

Deformation Twins Formed in Nanocrystalline Materials

2006 ◽  
Vol 503-504 ◽  
pp. 125-132 ◽  
Author(s):  
Yuntian T. Zhu
Keyword(s):  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Partial Dislocation ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Nucleation And Growth ◽  
Analytical Models ◽  
Partial Dislocations ◽  
Deformation Twins ◽  
Low Strain Rate

Deformation twins have been oberved in nanocrystalline (NC) Al synthsized by cryogenic ball-milling and in NC Cu processed by high-pressure torsion under room temperature and at a very low strain rate. They were found formed by partial dislocations emitted from grain boundaries. This paper first reviews experimental evidences on deformation twinning and partial dislocation emissions from grain boundaries, and then discusses recent analytical models on the nucleation and growth of deformation twins. These models are compared with experimental results to establish their validity and limitations.

Technique d'observation de surface in situ (TOSIS) :

1996 ◽  
Vol 84 ◽  
pp. 17-22
Author(s):  
A. Ranaivoarisoa ◽  
J. M. Olive ◽  
D. Desjardins
Keyword(s):  
Aqueous Solution ◽  
Crack Initiation ◽  
Grain Boundaries ◽  
Growth Rates ◽  
Triple Junction ◽  
Crack Nucleation ◽  
Initiation Time ◽  
Mesoscopic Scale ◽  
Crack Growth Rates

An optical method named In Situ Surface Observation Technique (ISSOT) is presented in this paper. This method is used to detect crack nucleation from a flaw (here a pit) at mesoscopic scale during a triangular push-pull cycling test under the control of charge amplitude in aqueous solution ofMgCl2 at 117°C. It can be found that the crack initiation time determined by using this technique represents 2 % of that estimated from a mechanical criterion. Moreover, the follow of the crack tip evolution by the ISSOT allows to measure average local crack growth rates. It has been shown that the variations of the latter were related to the effects of barriers such as grain boundaries, twin boundaries and grain boundaries triple junction.

Effect of titanium alloys elasticity modulus on warping of stamped blanks during cooling

2021 ◽  
pp. 221-227
Author(s):  
M.O. Smirnov ◽  
A.M. Zolotov ◽  
A.M. Tyukhtyaev
Keyword(s):  
Mathematical Modeling ◽  
Titanium Alloys ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Elasticity Modulus ◽  
Preliminary Deformation ◽  
Wide Spread ◽  
Temperature Dependences ◽  
Cumulative Deformation ◽  
The Difference

Wide spread in the values of the elasticity modulus of the titanium VT6 alloy and its analogs Ti—6Al—4V, Ti—6Al—4V ELI at room temperature and at elevated temperatures is revealed аs result of the literature sources analysis. The data are ambiguous, the available temperature dependences of the elasticity modulus have very different values starting from the temperature T l 500 °C. Mathematical modeling of the warping process is carried out on the example of figurine-shaped stamped blank of turbine blade using various dependences of the elasticity modulus on temperature. Cases of warping during cooling of stamped blank after cooling-down in stamp with and without cumulative deformation are considered. The difference in the course of thermal deformations during the cooling of the workpiece is obtained using different temperature dependences of the elasticity modulus. The presence of preliminary deformation increases the warping of the workpieces.

Segregation engineering enables nanoscale martensite to austenite phase transformation at grain boundaries: A pathway to ductile martensite

2013 ◽  
Vol 61 (16) ◽  
pp. 6132-6152 ◽  
Author(s):  
D. Raabe ◽  
S. Sandlöbes ◽  
J. Millán ◽  
D. Ponge ◽  
H. Assadi ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Grain Boundaries ◽  
Austenite Phase

scholarly journals Storage and Condition of Biomass Influence to Biosorption of Lead (II) and Zinc(II) by Saccharomyces cerevisiae Biomass

2010 ◽  
Vol 1 (1) ◽  
pp. 11-15
Author(s):  
Jasmidi Jasmidi ◽  
Eko Sugiharto ◽  
Mudjiran Mudjiran
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Atomic Absorption ◽  
Room Temperature ◽  
Final Concentration ◽  
Biomass Storage ◽  
Lead And Zinc ◽  
The Difference ◽  
Biomass Influence ◽  
And Storage ◽  
Zinc Storage

The influence of length and condition of Biomass Storage on the biosorption of lead and zinc that present together in a solution by Saccharomyces cerevisiae biomass were studied. In this experiment, variables of length and condition of biomass storage were examined. Concentration of lead and zinc were determined by atomic absorption spectrophotometric (AAS) using air-acetilene as atomizing flame. Loading of lead and zinc on the biomass were determined as the difference between the initial and the final concentration of lead and zinc in the solution. Biosorption of lead and zinc were influenced by condition and storage of the biomass. Storage of biomass in the room temperature for one week cause an increasing uptake. Storage for longer period result in decrease of lead and zinc uptake. Storage of biomass in a freezer up to 2 weeks increased the uptake of lead, but did not influence the uptake of zinc. Storage for longer period decreased the uptake of both of lead and zinc. For all condition the uptake of lead higher than the uptake of zinc by Saccharomyces cerevisiae.

scholarly journals The principal magnetic susceptibilities of neodymium sulphate octahydrate at low temperatures

1939 ◽  
Vol 170 (941) ◽  
pp. 266-271 ◽  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Energy Levels ◽  
Constant Factor ◽  
The Other ◽  
Crystalline Field ◽  
Cubic Symmetry ◽  
The Subject ◽  
The Difference ◽  
The One

The magnetic and other related properties of neodymium sulphate have been the subject of numerous investigations in recent years, but there is still a remarkable conflict of evidence on all the essential points. The two available determinations of the susceptibility of the powdered salt at low temperatures, those of Gorter and de Haas (1931) from 290 to 14° K and of Selwood (1933) from 343 to 83° K both fit the expression X ( T + 45) = constant over the range of temperature common to both, but the constants are not the same and the susceptibilities at room temperature differ by 11%. The fact that the two sets of results can be converted the one into the other by multiplying throughout by a constant factor suggested that the difference in the observed susceptibilities was due to some error of calibration. It could, however, also be due to the different purity of the samples examined though the explanation of the occurrence of the constant factor is then by no means obvious. From their analysis of the absorption spectrum of crystals of neodymium sulphate octahydrate Spedding and others (1937) conclude that the crystalline field around the Nd+++ ion is predominantly cubic in character since they find three energy levels at 0, 77 and 260 cm. -1 .* Calculations of the susceptibility from these levels reproduce Selwood’s value at room temperature but give no agreement with the observations-at other temperatures. On the other hand, Penney and Schlapp (1932) have shown that Gorter and de Haas’s results fit well on the curve calculated for a crystalline field of cubic symmetry and such a strength that the resultant three levels lie at 0, 238 and 834 cm. -1 , an overall spacing almost three times as great as Spedding’s.

scholarly journals Kenaf Fibre Reinforced Polypropylene Composites: Effect of Cyclic Immersion on Tensile Properties

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
W. H. Haniffah ◽  
S. M. Sapuan ◽  
K. Abdan ◽  
M. Khalid ◽  
M. Hasan ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Tensile Properties ◽  
Room Temperature ◽  
Tap Water ◽  
Tensile Modulus ◽  
Polypropylene Composites ◽  
Preliminary Results ◽  
Kenaf Fibre ◽  
The Difference ◽  
Number Of Cycles

This research studied the degradation of tensile properties of kenaf fibre reinforced polypropylene composites due to cyclic immersion into two different solutions, as well as comparison of the developed composites’ tensile properties under continuous and cyclic immersion. Composites with 40% and 60% fibre loadings were immersed in tap water and bleach for 4 cycles. Each cycle consisted of 3 days of immersion and 4 days of conditioning in room temperature (28°C and 55% humidity). The tensile strength and modulus of composites were affected by fibre composition, type of liquid of immersion, and number of cycles. The number of immersion cycles and conditioning caused degradation to tensile strength and modulus of kenaf fibre reinforced polypropylene composites. Continuous and cyclic immersion in bleach caused tensile strength of the composites to differ significantly whereas, for tensile modulus, the difference was insignificant in any immersion and fibre loadings. However, continuous immersion in the bleach reduced the tensile strength of composites more compared to cyclic immersion. These preliminary results suggest further evaluation of the suitability of kenaf fibre reinforced polypropylene composites for potential bathroom application where the composites will be exposed to water/liquid in cyclic manner due to discontinuous usage of bathroom.

Simulation of the interaction of plastic zone dislocations with the grain boundary at brittle-plastic transition temperatures in molybdenum

2021 ◽  
Vol 2021 (3) ◽  
pp. 77-85
Author(s):  
K. M. Borysovska ◽  
◽  
N. M. Marchenko ◽  
Yu. M. Podrezov ◽  
S. O. Firstov ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Grain Boundary ◽  
Plastic Zone ◽  
Grain Boundaries ◽  
Crack Tip ◽  
Dynamics Simulation ◽  
Density Of Dislocations ◽  
Grain Sizes ◽  
Pile Up

The (DD) method was used to model the formation of the plastic zone of the top of the cracks in polycrystalline molybdenum. Special attention was paid to take into account the interaction of dislocations in the plastic zone with grain boundaries. Structural sensitivity of fracture toughness was analyzed under brittle-ductile condition. Simulations were performed for a range of grain sizes from 400 to 100 μm, at which a sudden increase in fracture toughness with a decrease of grain size was experimentally shown. We calculated the value of K1c taking into account the shielding action of dislocations. The position of all dislocations in the plastic zone at fracture moment was calculated. Based on these data, we obtained the dependences of dislocation density on the distance from the crack tip thereby confirming significant influence of the grain boundaries on plastic zone formation. At large grain sizes, when the plastic zone does not touch the boundary, the distribution of dislocations remained unchanged. As grains reduce their size to size of the plastic zone, they start formating a dislocation pile – up near the boundaries. Dislocations on plastic zone move slightly toward the crack tip, but the density of dislocations in the middle of the grain remains unchanged, and fracture toughness remains almost unchanged. Further reduction of the grain size leads to the Frank-Reed source activation on the grain boundary Forming dislocation pile-up of the neighbor grains. Its stress concentration acts on dislocations of the first grain and causes redistribution of plastic zone dislocations. If the reduction in grain size is not enough to form a strong pile-up, density of dislocations on plastic zone increases slightly and crack resistance increases a few percent. Further reduction of grains promotes strong pile-up, dislocations move to crack tip, and its density on plastic zone increases. Crack is shielded and fracture toughness increases sharply. The calculation showed that the fracture toughness jump is observed at grain sizes of 100—150 μm, in good agreement with the experiment. Keywords: dislocation dynamics simulation, molybdenum, fracture toughness, grain size, plastic zone, brittle-ductile transition.

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