Effect of Grain Size on Mechanical Properties of Dual Phase Steels Composed of Ferrite and Martensite

MRS Advances ◽  
2016 ◽  
Vol 1 (12) ◽  
pp. 811-816 ◽  
Author(s):  
Myeong-heom Park ◽  
Akinobu Shibata ◽  
Nobuhiro Tsuji
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Tensile Test ◽  
Coarse Grained ◽  
Dual Phase ◽  
Fine Grained ◽  
Grain Sizes ◽  
Dp Structure ◽  
Dp Steels

ABSTRACTIt is well-known that dual phase (DP) steels composed of ferrite and martensite have good ductility and plasticity as well as high strength. Due to their excellent mechanical properties, DP steels are widely used in the industrial field. The mechanical properties of DP steels strongly depend on several factors such as fraction, distribution and grain size of each phase. In this study, the grain size effect on mechanical properties of DP steels was investigated. In order to obtain DP structures with different grain sizes, intercritical heat treatment in ferrite + austenite two-phase region was carried out for ferrite-pearlite structures having coarse and fine ferrite grain sizes. These ferrite-pearlite structures with coarse and fine grains were fabricated by two types of heat treatments; austenitizing heat treatment and repetitive heat treatment. Ferrite grain sizes of the specimens heat-treated by austenitizing and repetitive heat treatment were 47.5 µm (coarse grain) and 4.5 µm (fine grain), respectively. The ferrite grain sizes in the final DP structures fabricated from the coarse-grained and fine-grained ferrite-pearlite structures were 58.3 µm and 4.1µm, respectively. The mechanical behavior of the DP structures with different grain sizes was evaluated by an uniaxial tensile test at room temperature. The local strain distribution in the specimens during tensile test was obtained by a digital image correlation (DIC) technique. Results of the tensile test showed that the fine-grained DP structure had higher strength and larger elongation than the coarse-grained DP structure. It was found by the DIC analysis that the fine-grained DP structure showed homogeneous deformation compared with the coarse-grained DP structure.

Effect of Grain Size and Grain Boundary on Mechanical Yielding Behavior of Fully Stabilized Zirconia

2006 ◽  
Author(s):  
Jie Lian ◽  
Javier Garay ◽  
Junlan Wang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Boundary Effect ◽  
Coarse Grained ◽  
Stabilized Zirconia ◽  
Fine Grained ◽  
Grain Sizes ◽  
Reduced Modulus ◽  
Grain Boundary Effect

Mechanical properties of fully yttria stabilized zirconia (F-YSZ) with different grain sizes were investigated using instrumented indentation. While the grain size effect on the yield strength was performed on both the coarse-grained and fine-grained F-YSZ, the grain boundary effect was studied on the coarse-grained F-YSZ by performing nanoindentation within the grains and on/near the grain boundaries. Little variations were observed on mechanical properties such as hardness and reduced modulus, interesting results were obtained on the grain boundary effect on the yielding load for the course-grained F-YSZ.

Studies with the intraruminal selenium pellet. 2. The effect of grain size of selenium on the functional life of pellets in sheep

1981 ◽  
Vol 32 (6) ◽  
pp. 935 ◽  
Author(s):  
DR Hudson ◽  
RA Hunter ◽  
DW Peter
Keyword(s):  
Grain Size ◽  
Progressive Increase ◽  
Coarse Grained ◽  
Elemental Selenium ◽  
Average Composition ◽  
Plasma Selenium ◽  
Iron Selenide ◽  
Fine Grained ◽  
Grain Sizes

Grain size of elemental selenium is a major factor controlling the long-term effectiveness of intraruminal selenium pellets. Microscope studies of polished sections of new and used selenium pellets showed that two commercially manufactured pellets contained selenium with average grain sizes about 4 and 40 �m respectively. Plasma selenium concentrations in sheep treated with pellets containing the coarse-grained selenium were maintained at higher levels over longer periods of time than those measured for sheep treated with pellets with fine-grained selenium. Pellets removed from sheep after 2, 4, 8, 16 and 28 days showed a progressive increase in the degree of alteration of selenium to a compound of average composition (g/100 g) iron, 33.7; selenium, 51.3 ; oxygen, 15.0. After 28 days only a small percentage of elemental selenium remained in pellets with fine-grained selenium, whereas about 50% remained in pellets with coarse-grained selenium. CSIRO prototype pellets, for which long-term effectiveness had been established, also contained coarse-grained selenium, and remnants of selenium were found in pellets that had been in sheep for periods up to 3 years. Selenium, administered in gelatin capsules or as sachets containing glass-selenium mixtures, was stable under the pH-Eh conditions of the rumen, but was rendered unstable in selenium pellets or iron-selenium mixtures by the presence of iron. It is probable that the most rapid release of selenium to the sheep occurs as a result of a chemical reaction involving the oxidation of iron and concomitant alteration of elemental selenium to iron selenide.

Effect of alloy grain size on oxidation resistance of silica-coated stainless steel

1994 ◽  
Vol 52 ◽  
pp. 676-677
Author(s):  
C. S. McDowell ◽  
S. N. Basu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Stainless Steel ◽  
Oxidation Resistance ◽  
Powder Processing ◽  
Hot Isostatic Pressing ◽  
Silica Coating ◽  
Austenitic Steels ◽  
Coarse Grained ◽  
Fine Grained

Oxidation resistance of stainless steels, which rely on the formation of a Cr2O3 (chromia) scale, can be further improved through minor alloying additions such as Al or Si, or by application of coatings to the exposed surfaces. Although, additions of Si to austenitic steels have demonstrated an improvement in oxidation resistance, high Si contents can be detrimental to the mechanical properties of these alloys. The application of a silica coating on the surface of the stainless steel provides improved oxidation resistance without detrimental effects on the mechanical properties. This study examines the effect of the grain size of the stainless steel on the effectiveness of a silica coating as an oxidation barrier.Fully austenitic stainless steel of composition Fe-18(wt%)Cr-20Ni-1.5Mn was produced in both coarsegrained and fine-grained form. The coarse-grained alloy, with a grain size of approximately 100 μm, was produced by casting and hot rolling. The fine-grained alloy, with a grain size of approximately 5 μm, was produced by rapid solidification powder processing, followed by consolidated by hot isostatic pressing and swaging.

scholarly journals Grain Size Effect on the Mechanical Behavior of Cohesionless Coarse-Grained Soils with the Discrete Element Method

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Renjie Wen ◽  
Cai Tan ◽  
Yong Wu ◽  
Chen Wang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Shear Strength ◽  
Size Effect ◽  
Discrete Element Method ◽  
Discrete Element ◽  
Force Chain ◽  
Coarse Grained ◽  
Biaxial Compression ◽  
Grain Sizes

Biaxial compression tests with the same specimen size and different maximum grain sizes were simulated for coarse-grained soils using the discrete element method to study the influence of grain size on the mechanical properties and force chain. The maximum grain sizes were 40, 20, 10, and 5 mm, respectively. The grading with self-similar fractal structure in mass is designed to ensure the same pore structure for soils. The shear strength increased with the increase in maximum grain size. Evident increase in shear strength and significant size effect were observed when the ratio of the specimen diameter to maximum grain size was less than five. The shear dilation of coarse-grained soils increases with the increase in maximum grain size. The contact force distribution was uniform when maximum grain size was small but tends to be uneven with the increase in maximum grain size, thereby causing the increase in shear strength by stable strong force chains. This finding demonstrates size effect on the mechanical properties and force chain of cohesionless coarse-grained soils under the biaxial compression condition.

Grain Size Dependence of the Flow Stress of TWIP Steel

2010 ◽  
Vol 654-656 ◽  
pp. 294-297 ◽  
Author(s):  
Ghasem Dini ◽  
Rintaro Ueji ◽  
Abbas Najafizadeh
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Twip Steel ◽  
Strengthening Mechanism ◽  
Mechanical Twinning ◽  
Coarse Grained ◽  
Strengthening Effect ◽  
Fine Grained ◽  
Hardening Behavior ◽  
Grain Sizes

The effect of grain size on the flow stress in TWinning Induced Plasticity (TWIP) steel was investigated via the X-ray diffraction (XRD) measurements of dislocation density. The results indicated that the hardening behavior of fine grained samples (mean grain sizes in the range of 2.1-3.8μm) can be described as typical dislocation interactions. However in coarse grained samples (mean grain sizes in the range of 4.7-38.5μm) where extensive mechanical twinning occurs, another strengthening mechanism is required. Consequently, the effect of grain size on the flow stress parameters of the proposed equation was considered and it was found that in the fine grained samples, the Holloman analysis can describe the hardening behavior. However, in coarse grained samples, a second hardening term due to the strengthening effect of mechanical twin boundaries needs to be added to the Holloman equation.

scholarly journals Grain Size Effect of the γ Phase Precipitation on Martensitic Transformation and Mechanical Properties of Ni–Mn–Sn–Fe Heusler Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2339
Author(s):  
Jinpei Guo ◽  
Minting Zhong ◽  
Wei Zhou ◽  
Yajiu Zhang ◽  
Zhigang Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Martensitic Transformation ◽  
Annealing Time ◽  
Volume Fraction ◽  
Heusler Alloys ◽  
Coarse Grained ◽  
Dual Phase ◽  
Average Grain Size ◽  
Stress Hysteresis

Isothermal annealing of a eutectic dual phase Ni–Mn–Sn–Fe alloy was carried out to encourage grain growth and investigate the effects of grain size of the γ phase on the martensitic transformation behaviour and mechanical properties of the alloy. It is found that with the increase of the annealing time, the grain size and volume fraction of the γ phase both increased with the annealing time predominantly by the inter-diffusion of Fe and Sn elements between the γ phase and the Heusler matrix. The isothermal anneals resulted in the decrease of the e/a ratio and suppression of the martensitic transformation of the matrix phase. The fine γ phase microstructure with an average grain size of 0.31 μm showed higher fracture strength and ductility values by 28% and 77% compared to the coarse-grained counterpart with an average grain size of 3.31 μm. The fine dual phase microstructure shows a quasi-linear superelasticity of 4.2% and very small stress hysteresis during cyclic loading, while the coarse dual phase counterpart presents degraded superelasticity of 2.6% and large stress hysteresis. These findings indicate that grain size refinement of the γ phase is an effective approach in improving the mechanical and transformation properties of dual phase Heusler alloys.

scholarly journals Fine-grained dual-phase high-entropy ceramics derived from boro/carbothermal reduction

2020 ◽  
Author(s):  
Si-Chun Luo ◽  
Wei-Ming Guo ◽  
Kevin Plucknett ◽  
Hua-Tay Lin
Keyword(s):  
Mechanical Properties ◽  
Carbothermal Reduction ◽  
Dual Phase ◽  
Boride Phase ◽  
High Entropy ◽  
Fine Grained ◽  
Grain Sizes ◽  
Pinning Effect ◽  
Precursor Powders ◽  
Reduction Approach

Abstract In the current work fine-grained dual-phase, high-entropy ceramics (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C with different phase ratios are prepared from powders synthesized via a boro/carbothermal reduction approach, by adjusting the content of B4C and C in the precursor powders. Phase compositions, densification, microstructure, and mechanical properties have been investigated. Due to the combination of pinning effect and the boro/carbothermal reduction approach, the average grain sizes (0.5–1.5 µm) of the dual-phase high-entropy ceramics, were much smaller as compared with previously reported values. The dual-phase high-entropy ceramics with 15 mol% boride phase exhibit the highest Vickers hardness (24.21 GPa) and fracture toughness (3.2 MPa•m1/2).

Relationship of Microstructure and Mechanical Properties of Dual Phase Steel after Various Annealing Conditions

2017 ◽  
Vol 891 ◽  
pp. 176-181
Author(s):  
Martin Šebek ◽  
Peter Horňak ◽  
Svätoboj Longauer ◽  
Peter Zimovčák ◽  
Pavol Zahumenský
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Dual Phase Steel ◽  
Dual Phase ◽  
Austenite Grain Size ◽  
Annealing Conditions ◽  
Intercritical Region ◽  
Dp Steels ◽  
Relationship Of ◽  
Three Phases

The development of ultrafine ferrite grain size has become one of attractive way how to improve the behavior of dual phase (DP) steels. The other possible way how to enhance mechanical properties of DP steels is to modify the chemical composition. Therefore object of our investigation was the dual phase steel with modified alloying (three times higher Cr content with addition of phosphorus). The dual phase steel was annealed in laboratory conditions in accordance with three specified annealing cycles: into intercritical region (780°C), into austenite region (920°C) and into austenite region (920°C) by subsequently cooling into intercritical region (780°C) with the hold at the temperature of 495°C. The obtained microstructure after selected annealing regimes consists of three phases (ferritic matrix, martensite and martensite/bainite grains) with different size and distribution. For studied annealing regimes were clearly defined mechanical properties such as: YS, UTS, elongation, n-parameter and ratio YS/UTS. It was defined the scheme of microstructure evolution on base of austenite grain size during the continual cooling process with defined three phases: 1) the hard martensite formed on the grain boundary; 2) the soft interior bainite and 3) the hard isolated martensite.

scholarly journals Challenging Ultra Grain Refinement of Ferrite in Low-C Steel Only by Heat Treatment

2020 ◽  
Vol 7 ◽  
Author(s):  
Myeong-heom Park ◽  
Akinobu Shibata ◽  
Nobuhiro Tsuji
Keyword(s):  
Heat Treatment ◽  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Cyclic Heat Treatment ◽  
Austenite Grain Size ◽  
Fine Grained ◽  
Grain Sizes ◽  
Austenite Grain ◽  
Cyclic Heat

It is well-known that grain refinement is one of the most effective ways to improve strength of metals without addition of alloying elements. In order to obtain bulky metals having ultrafine grained (UFG) microstructures with average grain sizes smaller than 1 μm, severe plastic deformation (SPD) processes have made a great success. However, there are still big barriers to realize UFG metallic materials, especially UFG steels, in large scale industries, since severe plastic deformation processes usually need special techniques and equipment, and large deformation forces are required for heavy plastic deformations. Cyclic heat treatments to repeat martensitic transformation and austenitization have been known as a simple way to fabricate fine-grained austenitic structures in steels. In the present study, we tried to make final ferrite microstructures ultrafine in a low-C steel by means of the cyclic heat treatment. Evolution of microstructures during the cyclic heat treatment was systematically investigated, putting stress on the change of grain sizes of austenite and ferrite. The austenite grain size decreased with increasing the number of heat treatment cycles, and the minimum average austenite grain size obtained was 11 μm. By having furnace-cooling from austenite states with various grain sizes, ferrite microstructures with different mean grain sizes were fabricated. We could successfully obtain a fine-grained ferrite structure with a mean grain size of 4.5 μm and nearly a random texture through the heat treatment without deformation. Microstructural features and mechanical properties of the obtained fine-grained ferritic structures were investigated by scanning electron microscope/electron back-scattering diffraction measurements and a tensile test at room temperature. The specimens with ferrite + pearlite microstructure with the smallest average ferrite grain size of 4.5 μm managed both high strength (yield strength of 375 MPa and tensile strength of 500 MPa) and large tensile ductility (uniform elongation of 20% and total elongation of 39%) in the simple 2Mn-0.1C steel.

scholarly journals Structure and Mechanical Behavior of Bulk Nanocrystalline Materials

MRS Bulletin ◽  
1999 ◽  
Vol 24 (2) ◽  
pp. 44-53 ◽  
Author(s):  
J.R. Weertman ◽  
D. Farkas ◽  
K. Hemker ◽  
H. Kung ◽  
M. Mayo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Grain Size ◽  
Mechanical Behavior ◽  
Nanocrystalline Materials ◽  
Volume Fraction ◽  
Grain Boundary Sliding ◽  
Uniaxial Tensile ◽  
Fine Grained ◽  
Grain Sizes

The reduction of grain size to the nanometer range (˜2-100 nm) has led to many interesting materials properties, including those involving mechanical behavior. In the case of metals, the Hall-Petch equation, which relates the yield stress to the inverse square root of the grain size, predicts great increases in strength with grain refinement. On the other hand, theory indicates that the high volume fraction of interfacial regions leads to increased deformation by grain-boundary sliding in metals with grain size in the low end of the nanocrystalline range. Nanocrystalline ceramics also have desirable properties. Chief among these are lower sintering temperatures and enhanced strain to failure. These two properties acting in combination allow for some unique applications, such as low-temperature diffusion bonding (the direct joining of ceramics to each other using moderate temperatures and pressures). Mechanical properties sometimes are affected by the fact that ceramics in a fine-grained form are stable in a different (usually higher pressure) phase than that which is considered “normal” for the ceramic. To the extent that the mechanical properties of a ceramic are dependent on its crystal-lographic structure, these differences will become evident at the smaller size scales.It is uncertain how deformation takes place in very fine-grained nanocrystalline materials. It has been recognized for some time that the Hall-Petch relationship, which usually is explained on the basis of dislocation pileups at grain boundaries, must break down at grain sizes such that a grain cannot support a pileup. Even some of the basic assumptions of dislocation theory may no longer be appropriate in this size regime. Recently considerable progress has been made in simulating the behavior of extremely fine-grained metals under stress using molecular-dynamics techniques. Molecular-dynamics (MD) simulations of deformation in nanophase Ni and Cu were carried out in the temperature range of 300–500 K, at constant applied uniaxial tensile stresses between 0.05 GPa and 1.5 GPa, on samples with average grain sizes ranging from 3.4 nm to 12 nm.

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