Effect of Grain Refinement on the Mechanical Behaviour of Ferritic Steels: Evolution of Isotropic Hardening and Kinematic Hardening

2008 ◽  
Vol 584-586 ◽  
pp. 605-609 ◽  
Author(s):  
Olivier Bouaziz ◽  
A. Aouafi ◽  
Sebastien Allain
Keyword(s):  
Experimental Data ◽  
Grain Size ◽  
Grain Refinement ◽  
Mechanical Behaviour ◽  
Kinematic Hardening ◽  
Metallic Alloys ◽  
Isotropic Hardening ◽  
Ferritic Steels ◽  
Size Refinement ◽  
Fine Grain

New experimental data related to the grain size and the Bauschinger effects have been obtained for ferritic steels with grain size in the range of 3.5-22m. As the data show an increasing contribution of the kinematic hardening with grain size refinement, a new physical based model describing the isotropic hardening and the kinematic hardening is presented and validated with regard to the grain size. The consequences are discussed for fine grain metallic alloys.

Pertinence of the Grain Size on the Mechanical Strength of Polycrystalline Metals

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
N. A. Zontsika ◽  
A. Abdul-Latif ◽  
S. Ramtani
Keyword(s):  
Grain Size ◽  
Mechanical Strength ◽  
Kinematic Hardening ◽  
Uniaxial Stress ◽  
Isotropic Hardening ◽  
Ultrafine Grained ◽  
Consistent Model ◽  
Micromechanical Approach ◽  
Interaction Law ◽  
Small Deformations

Motivated by the already developed micromechanical approach (Abdul-Latif et al., 2002, “Elasto-Inelastic Self-Consistent Model for Polycrystals,” ASME J. Appl. Mech., 69(3), pp. 309–316.), a new extension is proposed for describing the mechanical strength of ultrafine-grained (ufg) materials whose grain sizes, d, lie in the approximate range of 100 nm < d < 1000 nm as well as for the nanocrystalline (nc) materials characterized by d≤100 nm. In fact, the dislocation kinematics approach is considered for characterizing these materials where grain boundary is taken into account by a thermal diffusion concept. The used model deals with a soft nonincremental inclusion/matrix interaction law. The overall kinematic hardening effect is described naturally by the interaction law. Within the framework of small deformations hypothesis, the elastic part, assumed to be uniform and isotropic, is evaluated at the granular level. The heterogeneous inelastic part of deformation is locally determined. In addition, the intragranular isotropic hardening is modeled based on the interaction between the activated slip systems within the same grain. Affected by the grain size, the mechanical behavior of the ufg as well as the nc materials is fairly well described. This development is validated through several uniaxial stress–strain experimental results of copper and nickel.

Practical Considerations on the Application of Ultrasonic Treatment to Mg-Al Shape Castings

2013 ◽  
Vol 765 ◽  
pp. 255-259
Author(s):  
Eraldo Pucina ◽  
Geoff de Looze ◽  
Dacian Tomus ◽  
Mark A. Easton ◽  
Andreas Schiffl ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Ultrasonic Treatment ◽  
Solidification Front ◽  
Al Alloys ◽  
Grain Refining ◽  
Fine Grain ◽  
Effective Form

This paper investigates the use of ultrasonic treatment on the grain refinement of Mg-Al alloys in castings similar to commercial gravity castings. It shows that it is a very effective form of grain refinement but it is limited spatially and by the advancing solidification front if partially-solidified product is washed into the die. It was found that the best way to obtain a homogeneous fine grain size through-out the casting was to combine a grain refining addition, SiC, with ultrasonic treatment during the initial stages of solidification.

Rosenhain Centenary Conference - 3. Materials development present and future 3.2 Controlled rolling

1976 ◽  
Vol 282 (1307) ◽  
pp. 289-303 ◽  
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Low Temperatures ◽  
Controlled Rolling ◽  
Processing Conditions ◽  
Materials Development ◽  
Fine Grain ◽  
Heat Treated ◽  
Grains Refinement ◽  
Major Consideration

Controlled rolling is a means whereby the properties of steel can be improved to a level equivalent to those of more highly alloyed or heat-treated steels. The processing conditions are controlled to refine the austenite structure and thereby give fine ferrite grains. Refinement of the structure is aided by the addition of micro-alloying elements such as Nb, V or Ti. The improved strength and toughness of controlled rolled steels are shown to be a result of the fine grain size. A further increase in strength beyond that due to grain refinement can be obtained by finishing rolling at low temperatures in the y + oc or cc regions. Commercial controlled rolling in various mill layouts, together with some properties obtained are described and it is pointed out that optimization of productivity is a major consideration when controlled-rollmg procedures are being planned.

Developing Superplasticity in Metallic Alloys through the Application of Severe Plastic Deformation

2008 ◽  
Vol 604-605 ◽  
pp. 97-111 ◽  
Author(s):  
Roberto B. Figueiredo ◽  
Megumi Kawasaki ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Elevated Temperatures ◽  
Metallic Alloys ◽  
Superplastic Flow ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Processing through the application of severe plastic deformation (SPD) provides an opportunity for achieving very significant grain refinement in bulk metals. Since the occurrence of superplastic flow generally requires a grain size smaller than ~10 µm, it is reasonable to anticipate that materials processed by SPD will exhibit superplastic ductilities when pulled in tension at elevated temperatures. This paper summarizes the fundamental principles of SPD processing and describes recent results demonstrating the occurrence of exceptional superplastic flow in these ultrafine-grained materials.

Dynamic Deformation Behavior of ECAPed AZ31 Magnesium Alloy

2014 ◽  
Vol 566 ◽  
pp. 104-109
Author(s):  
Hai Tao Hu ◽  
Feng Zhao ◽  
Ying Gang Miao ◽  
Tao Suo ◽  
Qiong Deng ◽  
...  
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Hardening ◽  
Grain Refinement ◽  
Rate Sensitivity ◽  
Dynamic Mechanical Properties ◽  
Angular Pressing ◽  
Fine Grain ◽  
Split Hopkinson ◽  
Dynamic Deformation Behavior

Equal channel angular pressing (ECAP) has been widely used for grain refinement in many alloys. In this article, the major emphasis was on the effect of grain size, temperature and strain rate on dynamic behavior of ECAPed AZ31. The dynamic mechanical properties of 6 pass and 8 pass ECAPed AZ31 were tested by split hopkinson pressing bar (SHPB) at wide temperatures range. At dynamic loading conditions, the ECAPed AZ31 shows strong strain hardening properties. The strain hardening rates decrease due to more slip systems’ opening with the increase of temperature. With the grain refinement, the fine-grain size and temperature show strong effect on the strain rate sensitivity.

Grain Refinement in Constrained Groove Pressing of 7050 Aluminum Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 2823-2826 ◽  
Author(s):  
Xiao Lei Dong ◽  
Bing Yun ◽  
Zhi Hao Ma
Keyword(s):  
Experimental Data ◽  
Grain Size ◽  
Regression Analysis ◽  
Aluminum Alloy ◽  
Grain Refinement ◽  
7050 Aluminum Alloy ◽  
Simulation Results ◽  
Refinement Effect

Constrained groove pressing is a simple and effective method of grain refinement. Using the experimental data obtained by regression analysis, this paper analyzes the simulation of the four pass constrained groove pressing deformation of 7050 aluminum alloy. The simulation results show that the grain size of the billet is refined significantly after four pass constrained groove pressing deformation and decreases from the original 90 μm to a minimum of 14.0 μm. With the increase of the number of deformation passes, refinement effect becomes weakened gradually, the grain size tends to stabilize and the organization is more uniform.

Microstructural Evolution in an Al-6061 Alloy Processed by High-Pressure Torsion and Rapid Annealing

2010 ◽  
Vol 667-669 ◽  
pp. 223-228 ◽  
Author(s):  
Aicha Loucif ◽  
Roberto B. Figueiredo ◽  
Thierry Baudin ◽  
François Brisset ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Grain Refinement ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Al 6061 ◽  
Fine Grain ◽  
Grain Structures ◽  
Average Grain Size ◽  
Continuous Recrystallization

The processing of bulk metals through the application of severe plastic deformation provides the opportunity for introducing significant grain refinement into bulk solids. In the present investigation, an aluminum alloy (Al-6061) was processed by high-pressure torsion (HPT) at room temperature under an applied pressure of 6.0 GPa up to a total of 5 turns. Detailed measurements after processing revealed the occurrence of continuous grain refinement and material strengthening with increasing imposed strain. The average grain size of the alloy was reduced from ~150 m to a grain size in the range of ~500 nm through processing by HPT. Although there was a difference in the average grain size of samples processed to different levels of imposed strain, careful inspection showed that the structures became similar after annealing at 250°C for 5 min. This suggests that the additional grain refinement introduced at large amounts of deformations is less stable at high temperatures. The results of this investigation, including the distributions of the grain sizes after annealing, are consistent with the predictions of a model based on the occurrence of continuous recrystallization in aluminum alloys having fine grain structures, large fractions of high-angle grain boundaries and where there is a large amount of deformation.

Microstructure Evolution in Undercooled Ni-Si Melt

2013 ◽  
Vol 749 ◽  
pp. 349-355
Author(s):  
Kai Fan ◽  
Feng Liu ◽  
Bao Quan Fu ◽  
Wen Zhong Luo ◽  
Yao He Zhou
Keyword(s):  
Experimental Data ◽  
Grain Size ◽  
Grain Refinement ◽  
Microstructure Evolution ◽  
Solid Solubility ◽  
Molten Glass ◽  
Dendrite Fragmentation ◽  
Equilibrium Solidification ◽  
Good Agreement ◽  
Non Equilibrium

Upon non-equilibrium solidification, the intrinsic parameters, such as moving velocity, temperature, solute partition coefficient, and liquid and solid concentrations at the interface, deviate from their equilibrium characteristics, and the morphology of the as-solidified structure and the grain size are influenced by the non-equilibrium liqulid/solid transformation, which further influences the subquent solidstate transformation. Adopting molten glass purification technology combined with cycle superheating method, the microstructure evolution of Ni-11at.%Si alloy in different undercooling was investigated. It was found that, with the increase of the initial undercooling, grain refinement occurred in microstructures of undercooled Ni-11at.%Si alloy. Meanwhile, the NL model was used to discuss the two different dendrite morphologies. According to Karmas model for dendrite fragmentation, the grain refinement of undercooled Ni-11at.%Si alloy was in good agreement with the experimental data, and the grain size was reduced with the increasing ΔT. The energy-dispersive spectroscopy (EDS) measurement was applied to analyze the solid solubility of Si atom in α-Ni matrix. It was found that the solid solubility of Si atom in α-Ni matrix increased with undercooling. At the undercooling of T>220K , a complete solute trapping occurred.

Modeling of grain refinement: Part II. Effect of nucleant particles—TiB2 additions for aluminum

2008 ◽  
Vol 23 (5) ◽  
pp. 1292-1300 ◽  
Author(s):  
X. Yao ◽  
S.D. McDonald ◽  
A.K. Dahle ◽  
C.J. Davidson ◽  
D.H. StJohn
Keyword(s):  
Experimental Data ◽  
Grain Size ◽  
Grain Refinement ◽  
Master Alloy ◽  
Commercial Purity ◽  
Grain Formation ◽  
Microstructure Morphology ◽  
The Relationship

Following the discussion of modeling grain refinement in Part I, [X. Yao, et al., J. Mater. Res.23(5), 1282, the effect of Al–Ti–B master alloy additions on grain formation in commercial-purity (CP) aluminum was investigated. The characteristics of the addition particles as applicable to the model are presented. The effect of adding TiB2 particles, the introduction of extra particles by reactions in the melt, and the effect of adding extra solute Ti are all modeled. The distribution of the potential particles and its effect on grain formation was also modeled to establish the relationship between the grain size and microstructure morphology and the additive characteristics. The calculated results are comparable with experimental data. Accordingly, possible mechanisms of grain refinement with Al–Ti–B refiners were proposed.

Effects of AlN Particles and Electromagnetic Stirring on As-Cast Structure of AZ31 Alloys

2011 ◽  
Vol 675-677 ◽  
pp. 771-774 ◽  
Author(s):  
Song Wei Gu ◽  
Hai Hao ◽  
Can Feng Fang ◽  
Shou Hua Ji ◽  
Xing Guo Zhang
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Grain Refinement ◽  
Grain Growth ◽  
Magnesium Alloys ◽  
Electromagnetic Stirring ◽  
Grain Refiner ◽  
Cast Structure ◽  
Fine Grain ◽  
Refinement Mechanism

A fine grain size generally leads to improved structural uniformity of magnesium alloys. AlN has been identified as a potential grain refiner and electromagnetic stirring may have great effects on microstructure and grain growth. This study will be focused on the effects of AlN particles and electromagnetic stirring on the as-cast structure of AZ31 alloys.The grain refinement mechanism of both methods on magnesium alloy and their interaction effects are also discussed.

Sign in / Sign up

Export Citation Format

Share Document