scholarly journals Mechanical properties, deformation and fracture mechanisms of bimodal Cu under tensile test

2021 ◽  
Vol 60 (1) ◽  
pp. 15-24
Author(s):  
Silu Liu ◽  
Yonghao Zhao
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Tensile Specimen ◽  
Deformation Mechanisms ◽  
Fracture Mechanisms ◽  
Fracture Angle ◽  
Area Reduction

Abstract Metals with a bimodal grain size distribution have been found to have both high strength and good ductility. However, the coordinated deformation mechanisms underneath the ultrafine-grains (UFGs) and coarse grains (CGs) still remain undiscovered yet. In present work, a bimodal Cu with 80% volume fraction of recrystallized micro-grains was prepared by the annealing of equal-channel angular pressing (ECAP) processed ultrafine grained Cu at 473 K for 40 min. The bimodal Cu has an optimal strength-ductility combination (yield strength of 220 MPa and ductility of 34%), a larger shear fracture angle of 83∘ and a larger area reduction of 78% compared with the as-ECAPed UFG Cu (yield strength of 410 MPa, ductility of 16%, shear fracture angle of 70∘, area reduction of 69%). Grain refinement of recrystallized micro-grains and detwinning of annealing growth twins were observed in the fractured bimodal Cu tensile specimen. The underlying deformation mechanisms for grain refinement and detwinning were analyzed and discussed.

Fracture Resistance of Wire-Wrapped Cylinders

1973 ◽  
Vol 95 (1) ◽  
pp. 219-226 ◽  
Author(s):  
A. K. Shoemaker ◽  
T. Melville ◽  
J. E. Steiner
Keyword(s):  
Yield Strength ◽  
Fracture Resistance ◽  
Crack Extension ◽  
Shear Fracture ◽  
Steel Wire ◽  
Crack Opening ◽  
High Strength ◽  
Opening Displacement ◽  
Propagating Crack ◽  
The Wire

Steel cylinders wrapped with steel wire have the capability of offering not only an economical high-strength structure, but also a structure with improved fracture resistance compared with that of an unwrapped cylinder of equivalent strength. Accordingly, 2000-psi-pressure hydraulic burst tests were therefore conducted to determine the fracture resistance of 36-in-dia, 60-ksi yield-strength, 1000-psi-pressure wire-wrapped cylinders at different levels of shell notch ductility, which was varied by testing at different temperatures. The cylinders were prestressed with 1/4-in-dia cold-drawn wire, and the shells contained part-through-wall flaws. A similarly flawed unwrapped cylinder was tested for comparison. The working-stress level was 72 percent of the specified minimum yield strength in the shell and 60 percent of the minimum tensile strength in the wire. The results showed that at a pressure double that of the unwrapped shell, no crack extension occurred at a temperature at which the steel exhibited fully ductile shell behavior (+110 deg F). A 2-ft crack extension occurred at a temperature (+10 deg F) at which the steel was still in the transition temperature range from ductile-to-brittle behavior (about 20 percent shear fracture), but a brittle crack (−70 deg F) propagated to the end of the wire-wrapped shell. Except for the brittle propagating crack, wire wrapping appears to provide sufficient constraint of a shell defect or propagating crack to limit bulging and crack-opening displacement. A model based on the compatibility in displacements between the crack opening and the local wire strain is presented for calculating the arrest conditions of the propagating crack in the test at 10 deg F. The same flaw size was critical at the constant failure pressure for all test temperatures, and showed that, as predicted, ductile initiation occurs even at the −70 deg F temperature in both the wrapped and unwrapped-cylinder tests. A circumferential flaw was shown to be less critical than a longitudinal flaw of the same size.

Discussions on Fracture Factors of Brittle Materials under the Shear-Compression Condition

2011 ◽  
Vol 250-253 ◽  
pp. 90-94
Author(s):  
Zhi Hui Li ◽  
Jun Ping Shi ◽  
An Min Tang
Keyword(s):  
Shear Stress ◽  
Stress State ◽  
Uniaxial Compression ◽  
Frictional Force ◽  
Shear Fracture ◽  
Maximum Shear Stress ◽  
Brittle Materials ◽  
Fracture Mechanisms ◽  
Initiation Point ◽  
Fracture Angle

Based on fundamental ideas in tribology and basic concept of stress state in solid mechanics, the existence of frictional force on shear plane is discussed under uniaxial compression of brittle materials. On account of macroscopic fracture forms and mesoscopic fracture mechanisms, the key factors influencing shear fracture angle are analyzed. The results show that, when brittle materials are compressed and shear fracture occurs, shear fracture surface at the crack initiation point is consistent with the maximum shear stress. But the reason of shear fracture angle examined in experiment greater than 45º lies in that, the existence of frictional force between endface of specimen and pressure head of testing machine, and additional tensile stress produced in the materials when harder crystalline grain wedge in softer medium have changed original uniaxial compression stress state and the direction of maximum shear stress on next fracture path.

Characterization of X80 Grade Linepipe Steel Coil With 24 mm Thickness

2012 ◽  
Author(s):  
Nuria Sanchez ◽  
Nenad Ilić ◽  
Martin Liebeherr
Keyword(s):  
Volume Fraction ◽  
Shear Fracture ◽  
High Strength ◽  
Microstructural Characterization ◽  
Steel Coil ◽  
Microstructural Parameters ◽  
High Toughness ◽  
Average Grain Size ◽  
Fracture Appearance

High strength and high toughness at low temperatures on heavy wall thickness skelp is required to build high pressure gas transportation pipelines. Detailed mechanical and microstructural characterization was carried on 24mm thick ArcelorMittal X80 coils in order to identify the microstructure control required to reach high toughness as determined by the shear fracture appearance after DWTT testing. Detailed microstructural characterization through thickness reveals that the microstructure gradient described by a systematic increase of the average grain size between surface and middle thickness of the strip and the increment of the volume fraction of M/A (martensite/ retained austenite) are the key microstructural parameters to control in order to ensure the adequate toughness of the material. The obtained high toughness of the coils indicates that the microstructure, controlled by an optimized rolling and cooling practice, is homogeneous through thickness of heavy wall linepipe grades.

Strengthening Mechanisms of Vanadium Micro-Alloyed Reinforcing Steel Bar

2011 ◽  
Vol 130-134 ◽  
pp. 942-945
Author(s):  
Lie Jun Li ◽  
Xiang Dong Huo ◽  
Lin Guo
Keyword(s):  
Yield Strength ◽  
Grain Refinement ◽  
Precipitation Hardening ◽  
High Strength ◽  
Experimental Methods ◽  
Strengthening Mechanisms ◽  
Large Numbers ◽  
Steel Bar ◽  
Micro Alloyed Steel ◽  
Grain Refinement Strengthening

High strength vanadium micro-alloyed steel with yield strength of 600MPa has been developed based on commercial 20MnSi steel bar. Experimental methods, such as OM, SEM and TEM, were used to study the experimental steels. Compared with 20MnSi, steel 20MnSiV boasts much finer microstructure, and large numbers of nanometer precipitates exist in the specimens of 20MnSiV. Analysis shows that strength of 20MnSiV dramatically increases through grain refinement strengthening and precipitation hardening of nanometer VCN particles.

Hall-Petch Relationship in an Al-Mg-Sc Alloy Subjected to ECAP

2014 ◽  
Vol 922 ◽  
pp. 120-125 ◽  
Author(s):  
Andrii Dubyna ◽  
Anna Mogucheva ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Refinement ◽  
Volume Fraction ◽  
Strain Range ◽  
High Strength ◽  
Strengthening Mechanisms ◽  
Dispersion Strengthening ◽  
Remarkable Effect ◽  
Petch Relationship ◽  
Angular Pressing ◽  
Average Size

Effect of extensive grain refinement on mechanical properties of an Al-Mg-Sc alloy subjected to equal-channel angular pressing (ECAP) at 300°C is considered in detail. It was shown that the Hall-Petch relationship with the coefficient, ky, of 0.2 MPa×m1/2 is valid in a wide strain range despite a great difference in deformation structures. Volume fraction of fine grains with an average size of ∼1 μm gradually increases with strain. It is caused by the fact that additive contributions of grain size strengthening and dislocation strengthening to the overall strengthening take place in this alloy. Upon ECAP the extensive grain refinement is accompanied by increasing dislocation density. Superposition of deformation and structural strengthening mechanisms provides achieving very high strength in the alloy. It was shown that ECAP at 300°C has no remarkable effect on a dispersion of coherent dispersoids. Al3(Sc,Zr), which gives a significant contribution to overall strength through dispersion strengthening. Contributions of different strengthening mechanisms to overall strength of the material are analyzed.

Grain Refinement in Austenitic Stainless Steel during Warm Screw Rolling

2012 ◽  
Vol 715-716 ◽  
pp. 889-894
Author(s):  
Anna Mogucheva ◽  
Nikolay Lopatin ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Screw Rolling ◽  
Structural Mechanism ◽  
Continuous Dynamic Recrystallization ◽  
Area Reduction ◽  
The Difference

The development of dynamic recrystallization in a 304-type austenitic stainless steel during warm multi-pass screw rolling was studied. The fraction recrystallized depended significantly on the distance from the centre of rolled rods. The highly elongated original grains were mainly observed in the centre of processed samples, while the portions close to the sample edge were characterized by relatively fast development of dynamic recrystallization leading to formation of almost equiaxed fine grains with a size of about 1 μm. The volume fraction of fine grains in the edge areas increased with straining and exceeded 0.7 after rolling to 63% cross area reduction. The structural mechanism responsible for the grain refinement was considered as continuous dynamic recrystallization. The difference in the recrystallization kinetics across the sample is associated with the variation in strain intensity.

Ti (CN) Precipitation in Ultra-High Strength Ti Micro-Alloyed Steels with 700MPa Yield Strength on TSCR Process

2013 ◽  
Vol 842 ◽  
pp. 61-69 ◽  
Author(s):  
Qi Lin Chen ◽  
Xin Ping Mao ◽  
Xin Jun Sun
Keyword(s):  
Yield Strength ◽  
Volume Fraction ◽  
High Strength ◽  
High Volume ◽  
Thermal Simulation ◽  
Cast Slab ◽  
Transmission Electron ◽  
The Matrix ◽  
Segregation Band ◽  
Physical And Chemical

Precipitates in ultra-high strength Ti micro-alloyed strips with 700MPa yield strength on TSCR process and in the thermal simulation experimental specimen are observed via Scanning Electronic Microscope (SEM) and Transmission Electron Microscope (TEM), the results show that: the precipitates in the Ti micro-alloyed cast slab thermal simulation experiment can be divided into three categories: 1) micron-sized liquation TiN, 2) 100-200nm sized TiC formed along original austenite grain boundaries or along the dendrite segregation band, 3) solid precipitated 50-100nm sized TiN. Deformation induced spherical TiC (about 10nm-30nm) homogeneously distributed in the matrix after the austenite deformation .After simulated coiling, dispersed TiC (about 5-15nm ) precipitated from ferrite are found in the specimen. TiN with hundreds of nanometers size are commonly found in Ti micro-alloyed strips in industrial production. Ti4C2S2and Ti (CN) are complex precipitated, Ti4C2S2size is less than 30nm; physical and chemical phase analysis shows that the nanosized TiC precipitates are characterized by high volume fraction and small dimensions.

ACHIEVING ULTRAFINE GRAIN SIZE IN Mg-Al-Zn ALLOY BY COLD DRAWING

2009 ◽  
Vol 23 (06n07) ◽  
pp. 927-933 ◽  
Author(s):  
HONGYING CHAO ◽  
YANG YU ◽  
ERDE WANG
Keyword(s):  
Grain Size ◽  
Strain Hardening ◽  
Grain Refinement ◽  
Annealing Temperature ◽  
High Strength ◽  
Cold Drawing ◽  
Ultrafine Grain ◽  
Area Reduction ◽  
Ultrafine Grain Size ◽  
Cold Area

Ultrafine-grain size of ~1µm was achieved in an AZ31B Mg alloy wires with high strength prepared by cold drawing and subsequent annealing in the present study. Effects of cold-drawn area reduction (CAR) on strain hardening, recrystallized grain refinement and annealing temperature were investigated. The results showed that the maximum cold area reduction as high as 65.1% could be reached at room temperature, which resulted in the notable strain hardening, grain refinement and the decrease of annealing temperature.

Microstructure and Yield Strength Evolution of Aluminum Alloys

2019 ◽  
Author(s):  
Kai Li ◽  
Yong Du ◽  
Min Song
Keyword(s):  
Aluminum Alloys ◽  
Yield Strength ◽  
Volume Fraction ◽  
Weight Ratio ◽  
High Strength ◽  
Industrial Applications ◽  
Dynamic Strain ◽  
Dynamic Strain Ageing ◽  
Architectural Structures ◽  
Strength Modeling

Aluminum alloys are light materials with high strength-to-weight ratio, corrosion resistance, and excellent formability. Due to these advantages, they are widely used in many industrial applications such as fabrication of aeroplanes, automobiles, ships, and architectural structures. Many fabrication parameters, such as alloy composition, casting and solidification conditions, strain rate, and ageing conditions, strongly affect the microstructural features such as morphology of phases, solute-dislocation interactions, as well as size and volume fraction of strengthening precipitates, and therefore determine the mechanical properties especially yield strength. This chapter probes microstructural optimization of aluminum alloys and the relationship between their microstructures and yield strength, with emphases on recent progress in microstructural modification of Al-Si alloys, yield strength modeling of dynamic strain ageing in Al-Mg alloys, and modeling of precipitate strengthening in Al-Mg-Si(-Cu) alloys.

Grain Refinement in Titanium-Erbium Alloys

1974 ◽  
Vol 32 ◽  
pp. 522-523
Author(s):  
B. B. Rath ◽  
J. E. O'Neal ◽  
R. J. Lederich
Keyword(s):  
Electron Microscopy ◽  
Size Distribution ◽  
Grain Refinement ◽  
Grain Growth ◽  
Volume Fraction ◽  
Pure Titanium ◽  
Systematic Investigation ◽  
Second Phase ◽  
Titanium Matrix ◽  
Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

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