Dynamic Recovery Mechanism Research Articles

Microstructure and mechanical properties of Al-Mg-Si alloy during solution heat treatment and forging integrated forming process

The integrated forming process of an Al-Mg-Si alloy was designed, which combined solution heat treatment (SHT) and hot forging into one operation followed by artificial aging. The effect of deformation strains on the microstructure and mechanical properties was investigated by electron backscatter diffraction (EBSD), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile tests. The results show that the tensile strength and yield strength of the compressed specimens were increased by at least 12.9% and 13.8%, respectively, when compared to the undeformed T6 specimen. {001}〈110〉 and {011}〈110〉 texture components were produced at low strains and gradually vanished as strain increased, in contrasting to the T6 specimen, which produced strong recrystallized texture components. As a result of the dynamic recovery (DRV) mechanism, intense {112}〈110〉 and {111}〈110〉 texture components were obtained in the integrally processed specimens at high strains along with a high fraction of low angle grain boundaries (LAGBs). The dispersed Al12(Fe,Mn)3Si phases aided in the formation of cellular structures and facilitated in the development of the DRV. The dislocations significantly accelerated the precipitation of β'' phases, which conversely pined the movement of dislocations and improved the mechanical properties of the Al-Mg-Si alloy.

Analytic model of dislocation density evolution in fcc polycrystals accounting for dislocation generation, storage, and dynamic recovery mechanisms

An analytic model of the evolution of dislocation density in fcc polycrystals is described. The evolution equations approximately account for most known dislocation storage, dynamic recovery, and dislocation generation mechanisms in fcc polycrystals. Specifically, the model incorporates network (forest) and grain boundary storage, mobile-network and mobile–mobile annihilation, screw–screw annihilation via athermal and thermal single cross-slip, generation by double cross-slip (Koehler mechanism, including dipole formation), Frank-Read sources, grain boundary nucleation, and mobile–immobile dislocation nucleation due to shock loading. Single cross-slip is assumed to proceed through the Friedel–Escaig (FE) mechanism; the corresponding activation energy is calculated using a modified FE model. The activation energy for double cross-slip is calculated for the first time by extending the FE model. The exact evolution equations are integro-differential equations, and as such are difficult to implement in a code; hence, the evolution equations are simplified by making several approximations. Preliminary results on copper are presented, including comparisons to experimental data.

Hot deformation behaviour and microstructure evolution of Al-3%Mg2Si alloy

To investigate the hot deformation behaviour of Al-3%Mg 2 Si, isothermal compression tests were carried out in the temperature range of 300–500 °C and strain rate range of 0.01–5 s −1 . The deformed microstructures were characterized by optical microscope, scanning electron microscope, transmission electron microscope and electron backscatter diffraction. The results show that the flow stress curves reveal a typical dynamic recovery characteristic. A modified Arrhenius-type constitutive equation was built to describe the flow behaviour of Al-3%Mg 2 Si alloy. Furthermore, based on the processing map of Al-3%Mg 2 Si alloy established under the strain of 0.8, microstructure evolution was analyzed. The high efficiency of power dissipation regions is mainly due to the softening mechanism of dynamic recovery and partial dynamic recrystallization. Mg 2 Si particles also play a positive role in dynamic recrystallization. The damage mechanism of unstable domains is the fracture and debonding of Mg 2 Si particles. • A modified constitutive model was built to describe the rheological properties of Al-3%Mg 2 Si alloy. • The softening mechanism is dominated by DRV with partial dynamic recrystallization. • Mg 2 Si particles play a positive role in dynamic recrystallization. • The damage mechanism of unstable domains is fracture and debonding of Mg 2 Si particles.

Microstructure Evolution and a Unified Constitutive Model of Ti-55511 Alloy Compressed at Stepped Strain Rates.

The flow behavior and microstructure change of the Ti-55511 alloy are investigated by thermal compression experiments with stepped strain rates. The phase transformation features, the dynamic recrystallization (DRX) behavior of the β matrix, the dynamic spheroidization mechanism of the lamellar α phase and the evolution of the β sub-grain size are quantitatively analyzed. A unified constitutive model is constructed to characterize the hot deformation features of the Ti-55511 alloy. In the established model, the work hardening effect is taken into account by involving the coupled effects of the equiaxed and lamellar α phases, as well as β substructures. The dynamic softening mechanisms including the dynamic recovery (DRV), DRX and dynamic spheroidization mechanisms are also considered. The material parameters are optimized by the multi-objective algorithm in the MATLAB toolbox. The consistency between the predicted and experimental data indicates that the developed unified model can accurately describe the flow features and microstructure evolution of the hot compressed Ti-55511 at stepped strain rates.

An Innovative Approach of Parameter Loading Path Design for Grain Refinement and Its Application in Ni80A Superalloy.

In order to obtain the desired mechanical properties of products, an innovative method of loading parameter designs for acquiring the desired grain refinement is proposed, and it has been applied in the compression process of Ni80A superalloy. The deformation mechanism maps derived from processing maps based on the Dynamic Materials Model (DMM) theory were constructed, since the critical indicator values corresponding to dynamic recrystallization (DRX) and dynamic recovery (DRV) mechanisms were determined. The processing-parameter domains with DRX mechanisms were separated from the deformation mechanism map, while such domains were chaotic and difficult to apply in innovative parameter loading path design. The speed-loading path derived from strain rate-loading path in a compression process was pursued. The grain refinement domains are discretized into a finite series of sub-domains with clear processing parameters, and the optimal strain rate of each sub-domain is determined by step-by-step finite element simulation. A 3D response surface of the innovative optimal loading path of strain rate was fitted by interpolating methods. Finally, the isothermal compression experiments for Ni80A superalloy were conducted, and the microstructure observations indicated that the desired grain refinement was achieved. This innovative method of parameter loading path design contributes to the microstructure adjustment of the alloys with DRX mechanism.

A modified constitutive model coupled with microstructure evolution incremental model for machining of titanium alloy Ti–6Al–4V

• A modified constitutive model that considers work hardening, dynamic recovery and dynamic recrystallization mechanism is proposed. • The constitutive model provides an interface to response of flow stress on microstructure evolution. • Incremental formulation of the JMAK model is proposed to capture microstructure evolution during cutting process. The altered microstructure during machining process had an inverse influence on materials behavior, machining forces and surface integrity. Thus, a constitutive model which builds the response of flow stress on microstructure evolution is gaining rising interest. Based on Johnson-Cook model, a modified constitutive model coupled with microstructure evolution incremental model for machining of Ti-6Al-4V is proposed. The competing effect of work hardening and dynamic recovery mechanism on flow stress is accentuated in the constitutive model. And a new softening term is introduced to describe material softening behavior caused by dynamic recrystallization. In addition, the modified constitutive model builds the response of flow stress on microstructure evolution by introducing the dynamic recrystallization volume fraction as an internal state variable. Considering the complex and variable loading conditions during the cutting process, the incremental formulation of the Johnson-Mehl-Avrami-Kolmogorov model is proposed to capture microstructure evolution during cutting process. Subsequently, orthogonal cutting experiments and simulations of Ti-6Al-4V have been carried out to evaluate the effectiveness of the proposed model. Simulation results show that the modified constitutive model has accurate predictions of the cutting and thrust forces and illustrates that DRX is the inducement of serrated chip formation. In addition, the modified model is able to simulate the microstructure evolution during Ti-6Al-4V cutting process, which is attractive for surface integrity research of cutting operations.

New insights on the laser powder bed fusion processing of a NiTi alloy and the role of dynamic restoration mechanisms

NiTi alloys are a remarkable class of materials capable of exhibiting unique behaviors such as shape memory effect and superelasticity. Laser powder bed fusion (L-PBF), as one of the most prominent additive manufacturing processes, has been recently used by many researchers to fabricate high-quality NiTi alloys with desired properties. In this research, those findings were exploited to utilize an optimum range of volumetric energy density to produce dense parts and offer new insights into the microstructure and properties of the fabricated parts. Although the development of high residual stresses has been frequently reported, the effects of those stresses on the microstructural evolution of NiTi parts during the process have been rarely discussed. By utilizing finite element and analytical approaches, it was predicted that the driving force for the activation of restoration mechanisms, namely dynamic recovery and recrystallization, is provided at elevated temperatures, and the temperature range in which those mechanisms occur was calculated. Detailed microstructural investigations confirmed the results, revealing columnar grains along the building direction with strong substructures caused by dynamic recovery, in addition to new recrystallized grains at boundaries of the melt pools and scanned tracks. It was concluded that dynamic recovery acts as the dominant restoration mechanism during L-PBF of NiTi alloys, affecting both the microstructure and mechanical properties of the final part. Additionally, the peak temperature of the melt pool is a paramount factor that, if increased, results in further progress of the dynamic recovery mechanisms.

Analysis of flow stress and microstructure evolution of 9310 steel during the hot compression

Due to the low-cost and high-strength of carburizing 9310 steel, it has become widely used in the manufacturing industry especially gears and shafts manufacturing. Hence, this paper investigates the hot deformation behavior and microstructure evolution of the 9310 steel under hot compression conditions. With the help of a combination of standard compression testing, optical microstructure and electron backscatter diffraction (EBSD) observation experiment, the dynamic recrystallization (DRX) and dynamic recovery (DRV) mechanisms of the 9310 steel under compressive stress were determined and the constitutive equation model was also identified. It was found that the peak stress level, steady flow stress, dislocation density and number of substructures of the alloy increases with the decreasing of deformation temperature and the increasing of strain rate. Conversely, the high angle grain boundary area becomes larger, the grain boundary forms a serrated shape and the DRX in the alloy occurs. This comprehensive characterization of stress and phase transformation could enable a precise control of the microstructures of 9310 steel, and hence its properties.

Hot Deformation Behavior of Cu-2.7Be Alloy during Isothermal Compression

The hot deformation behavior of Cu-2.7Be alloy was studied through isothermal hot compression experiments under various temperature and strain rate conditions. To predict and investigate the flow stress behavior, modified Johnson–Cook, Arrhenius-type, and artificial neural network models were used. The predictabilities of the models were assessed considering the parameters of average absolute relative error, correlation coefficient, and relative error. Among the three constitutive models, the ANN model was revealed to be the most accurate. According to the results of the dynamic material model theory, the hot processing of Cu-2.7Be alloys achieved its maximum efficiency (~60%) under a strain rate of 0.6 s−1, temperature range of 1023-1073 K, and the logarithm of strain rate in the range (− 1.25)-(− 0.25) s−1. Microstructural analysis indicated that the temperature and strain rate factors significantly affected the primary dynamic softening mechanism of the Cu-2.7Be alloys, following hot compression processing. At temperatures below 973 K, the Cu-2.7Be alloy primarily obeyed the dynamic recovery mechanism. Furthermore, the predominant mechanisms followed by the samples under the temperature/strain rate conditions of 973/0.1 and 1073 K/0.1 s−1 were continuous dynamic recrystallization and discontinuous dynamic recrystallization, respectively.

Microstructure evolution and constitutive relation establishment of Mg–7Gd–5Y–1.2Nd–0.5Zr alloy under high strain rate after severe multi-directional deformation

At room temperature, dynamic mechanical response of Mg–7Gd–5Y–1.2Nd–0.5Zr alloy under high strain rate after severe multi-directional deformation were measured by a Split-Hopkinson pressure bar equipped with a set of limited strain rings under the strain rates of 0.001, 1800, and 2300 s−1 along the extrusion direction (ED). An electron back-scattering diffraction and a transmission electron microscopy were used to characterize the microstructure evolution of the alloy. When compressed along ED direction at the strain rate of 2300 s-1, prismatic and pyramidal < a > slip mechanisms first occurred in the ultra-fine grain band, and then tensile twins, basal slip, prismatic slip, pyramidal slip, dynamic recovery, and recrystallization occurred in the equiaxed fine-grained region. At the same strain rate (7% strain), various deformation mechanisms in the ultra-fine grain region and equiaxed fine-grained region, as well as the dynamic recovery and recrystallization mechanisms in the equiaxed fine-grained region were strengthened with the increase of strain rate. Based on the phenomenological Johnson–Cook relationship and the microstructure evolution analysis during deformation, a new constitutive relation was constructed by inserting a softening term with strain into the formula to calculate the stress–strain curve, which was in good agreement with the experimental data.

Dynamic Softening Mechanism and an Improved Unified Constitutive Model for an Al–Cu–Mn–Fe–Zr Alloy during Warm Deformation

Deformation behavior of an Al–Cu–Mn–Fe–Zr alloy is investigated by plane strain compression tests at a warm deformation region. The flow stress first increases and then keeps steady, and the flow stress increases with reducing temperature or raising strain rate. However, the influence of strain rate on flow stress is weak at 100 and 150 °C. The dynamic recovery (DRV) mechanism is the dominant mechanism to balance the work hardening, and a larger number of dislocations are consumed at low strain rates. So, the deformed grains are difficult to reach the critical strain for dynamic recrystallization (DRX). When the strain rate is relatively high, the critical strain can be reached in a short time, which promotes the process of DRX. In addition, an improved unified constitutive model is built based on the evolution of dislocation density. The predicted flow stresses are in a close agreement with the measured results, proving that the built model can nicely reproduce the flow behavior.

Effect of multi-directional hot forging process on the microstructure and mechanical properties of Al–Si based alloy containing high amount of Zn and Cu

Abstract In this study, the hypoeutectic Al–7Si based alloy containing Zn and Cu was severely deformed with multi-directional forging (MDF) process at 200 °C. The samples were placed into an open die allowing the free deformation in only one direction and forged with hydraulic press at cumulative strains of 2.07, 4.14 and 6.21. The microstructural examinations were performed with X-ray diffractometer, optical, scanning and transmission electron microscopies while their strength properties were determined by tensile and hardness tests. MDF led to a refinement in α-Al grains, hard Si, Al7Cu2Fe and Al2Cu particles of crystallization origin. This process also provided a method for formation of secondary precipitates within the alloy's microstructure. It was determined that MDF increased the tensile properties of the alloy but decreased its hardness. On the other hand, this process converted brittle type fracture of homogenized alloy to ductile type. These results were explained in terms of grain boundary strengthening, precipitation hardening, refining of hard particles, and softening in matrix due to dynamic recovery and recrystallization mechanisms.

Influence of intra-granular void distribution on the grain sub-structure of UO2 pellets after high temperature compression tests

The aim of this work is to study the role of intra-granular voids on the macroscopic behavior and the microstructure of uranium dioxide (UO2) for different strain conditions in the high temperature dislocational creep regime.Two batches (B1 and B2) of stoichiometric UO2 pellets were fabricated by adapted powder metallurgy processes to obtain very close mean grain size and porosity but different fractions of intra-granular voids: they were 2.5 times more numerous in the second batch. The pellets were then compressed at 1773 K mostly in the dislocational regime for different strain levels and strain rates. Large Electron BackScattered Diffraction (EBSD) maps were acquired to quantify the sub-boundaries fraction in each deformed sample (with reliable detection of disorientation lines down to 0.25°). Accurate-Electron Contrast Channeling Image (Accurate-ECCI) experiments were also performed to evidence the arrangement of dislocations in the sub-boundaries and highlight their interaction with intra-granular voids. The fractions of sub-boundaries and their disorientation increased in both batches with increasing strain levels and strain rates. This confirms that during creep, UO2 is subject to a dynamic recovery mechanism. Interestingly, for similar deformation conditions, the pellets from batch B2 crept slower than those from batch B1. They also had a higher fraction of sub-boundaries which were more tortuous and located essentially close to the grain boundaries where the voids clustered. This suggests an influence of intra-granular voids on the creep rate, probably due to a void pinning effect of dislocation sub-boundaries. This effect should be taken into account to optimize the microstructure and mechanical properties of UO2 nuclear fuel, in order to improve its behavior under irradiation.

Mechanistic study of the effects of dynamic fluid/fluid and fluid/rock interactions during immiscible displacement of oil in porous media by low salinity water: Direct numerical simulation

Low salinity waterflooding (LSWF) is a process in which by lowering the ionic strength and/or manipulation of the composition of the injection water, the long term equilibrium in oil/brine/rock system is disturbed to reach a new state of equilibrium through which the oil production will be enhanced due to fluid/fluid and/or rock/fluid interactions. In spite of recent advances in the simulation of the LSWF at core scale and beyond, there are very few works that have modelled and simulated this process at the pore scale specially using direct numerical simulation (DNS). As a result the effects of wettability alteration and/or Interfacial Tension (IFT) change on the distribution of the phases at pore scale, as well as dynamics and mechanisms of the oil displacements in porous media are neither thoroughly investigated nor well understood. With this objective, the present study takes into account modelling both rock/fluid (dynamic contact angle) and fluid/fluid (dynamic oil/water IFT as well as diffusion between high salinity and low salinity water) interactions. Additionally, the proposed model is capable to effectively capture the time scale pertinent in the wettability alteration by LSWF via reaction rate and near solid surface diffusion coefficients. The model is developed and incorporated into OpenFOAM and both the Navier-Stokes equation for oil/water two-phase flow and the advection-diffusion equation for ion transport are solved. The developed model is validated against one dimensional (1D) sinusoidal micromodel experiments reported in the literature, and then applied to two dimensional (2D) heterogeneous micromodel to investigate the sole effect of wettability alteration as well as its coupled effect with IFT variations. Different degrees of contact angle alteration, different trends of IFT variations reported in the literature, as well as different injection scenarios (secondary or tertiary) are considered. 1D sinusoidal micromodel simulations visualize a dominant dynamic recovery mechanism which boosts the low salinity effect (LSE) via coalescence of the detached or partially detached residual oil blobs which forms a large oil ganglion towards the downstream and can effectively produce the residual oil saturation at shorter period of time compared to the case if such a coalescence didn't happen. The sensitivity analysis in 2D heterogeneous micromodel shows that the performance of the LSWF is a function of the degree of wettability alteration as well as IFT variations. Although the IFT decreasing trend with salinity can enhance the oil production through synergetic effect, the IFT increasing trend has a detrimental effect on the oil production and surpasses the effectiveness of wettability alteration interactions. The results confirm the importance of fluid/fluid interactions such as IFT variation on the LSE which has been previously ignored in numerical simulation LSWF altogether. The presented simulations shed the lights to the reasons behinds some of the discrepancies reported in the literature.

Dynamic restoration of the ferrite and austenite phases during hot compressive deformation of a lean duplex stainless steel

The active restoration processes within the ferrite and austenite phases were investigated in a Ni-free duplex stainless steel with the 75/25 austenite/ferrite ratio performing compression tests over the wide range of temperature and strain rate (700–1000 °C and 0.001–0.1s−1, respectively). The substructural features under different Zener-Hollomon parameters (Z) were examined using the electron backscatter diffraction analysis. A significant portion of flow softening was attributed to the active softening mechanisms in the continuous network of ferrite phase. The ferrite was softened through continuous dynamic recrystallization (CDRX) at high Z values, but the dynamic recovery (DRV) surmounted CDRX at low Z parameters. Interestingly, the discontinuous dynamic recrystallization (DDRX) mechanism was testified by increasing temperature and strain rate, i.e. at medium Z values. DDRX occurred by the growth of high-angle subgrains near the austenite/ferrite interfaces. With decreasing Z values, an increase in subgrain and grain sizes was observed. Contrarily to ferrite, the austenite phase was softened mostly through the dynamic recovery mechanism. At higher Z values microband arrays were formed in austenite holding specific character resembling to band-like misorientation gradients. However, under the lower Z values, a small fraction of recrystallized grains was formed through the CDRX/DDRX mechanisms. This was justified considering the lower strain accommodation in the austenite phase during deformation of duplex stainless steel.

Hot deformation behavior and processing map of Zr-4 alloy

The hot deformation behavior of Zr-4 alloy at the deformation temperature range of 750–1000 °C and the strain rate range of 0.001–10 s−1 was studied on a Gleeble-3500 thermal simulator. The results show that the flow stress increases with the increasing strain rates or the decreasing deformation temperature. Based on the experimental data, the strain-compensated constitutive equation was established to predict flow stress during different strains, strain rates and temperatures. Meanwhile, the hot deformation activation energy of Zr-4 alloy was respectively calculated to be 224.31 kJ/mol, 593.50 kJ/mol and 345.71 kJ/mol in α single-phase region, α+β two-phase region and β single-phase region, which are obviously much higher than the activation energy of pure zirconium (113 kJ/mol). It indicates that the main deformation mechanism is not the dynamic recovery but other deformation mechanisms. According to the dynamic material model and Murty instability criterion, Murty processing maps have been constructed at the true strain of 0.6 and 1.2. Moreover, by combining microstructural observations, the areas of 750–880 °C/0.01–0.32 s−1 and 900–1000 °C/0.03–1 s−1 are identified to be the optimum hot working parameters.

Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel

It is well recognized the importance of the rheological characterization for the development of the steel in thermomechanical treatments, especially for the mechanical properties improvement of bainitic steels in subsequent hot forging optimization. Therefore, the plastic strain behaviour of a low carbon high silicon bainitic steel was studied through isothermal compression tests using a thermomechanical simulator at temperatures of 1123 K – 1423 K and strain rates of 0.1 – 5 s-1. Arrhenius equation was used to obtain the constitutive constants, which represents the material behaviour of flow stress in high temperature. Besides, work hardening, dynamic recovery, and the JMAK model in the dynamic recrystallization (DRX) of the steel parameters were determined. The second part of this research compared two proposed modified models from the literature, which showed the differences in modelled flow curves behaviour when they are applied for high strain levels. The flow curves were modelled in high strain levels for further implementation in numerical simulation, thus allowing an adjustment of parameters in hot forming processes for this bainitic steel. The proposed models presented an agreement with experimental values. However, only the Avrami equation to DRX showed the dynamic recovery mechanism in high strain levels, which has represented physical behaviour during the thermomechanical process.

Resilience Assessment of Interdependent Infrastructure Systems: A Case Study Based on Different Response Strategies

Resilient infrastructure systems are essential for continuous and reliable functioning of social and economic systems. Taking advantage of network theory, this paper models street network, water supply network, power grid and information infrastructure network as layers that are integrated into a multilayer network. The infrastructure interdependencies are described using five basic dependence patterns of fundamental network elements. Definitions of dynamic cascading failures and recovery mechanisms of infrastructure systems are also established. The main contribution of the paper is a new infrastructure network resilience measure capable of addressing complex infrastructure system, as well as network component (layer) interdependences. The new measure is based on infrastructure network performance, proactive absorptive capacity and reactive restorative capacity, with three resilience features of network—robustness, resourcefulness, and rapidity. The quantitative resilience measure using dynamic space-time simulation model is illustrated with a multilayer infrastructure network numerical test, including different response strategies to floods of different scale. The results demonstrate that the resilience measure provides an evaluation method of various protection and restoration strategies that will optimize the performance of interdependent infrastructure system. The sector-specific decisions could not always lead to optimal system solutions, and systems approach offers significant benefits for increasing infrastructure system resilience. This study can assist municipal decision makers in (i) better understanding the effects of different response strategies on the resilience of interdependent infrastructure system, and (ii) deciding which strategy should be adopted under different types of disasters.

Constitutive Model and Processing Maps for a Ti‐55511 Alloy in β Region

The flow behavior of a high‐strength Ti alloy (Ti‐55511) in the β region is studied by hot compressive experiments. A dislocation density–based constitutive equation, together with processing maps, is established to describe the flow behavior and hot workability of the studied Ti alloy. It is found that the strain rate () and temperature (T) distinctly influence the hot compressive deformation behavior. The flow stress increases distinctly with a rising or reducing T. The main softening mechanism in the β region is dynamic recovery (DRV). The established constitutive equation based on the work hardening (WH) and DRV mechanisms has the desired prediction accuracy, and the correlation coefficient between the predicted and experimental results is 0.9912. The processing maps indicate that a high strain rate (0.4–10 s−1) easily causes unstable deformation, whereas low and medium strain rates (0.001–0.2 s−1) are suitable for hot compressive deformation of the studied alloy.

A Crystal-Plasticity Cyclic Constitutive Model for the Ratchetting of Polycrystalline Material Considering Dislocation Substructures

A crystal-plasticity cyclic constitutive model of polycrystalline material considering intra-granular heterogeneous dislocation substructures, in terms of three dislocation categories: mobile dislocations, immobile dislocations in the cell interiors and in the cell walls, is proposed based on the existing microscopic and macroscopic experimental results. The multiplication, annihilation, rearrangement and immobilization of dislocations on each slip system are taken as the basic evolutionary mechanism of the three dislocation categories, and the cross-slip of screw dislocations is viewed as the dynamic recovery mechanism at room temperature. The slip resistance associated with the isotropic hardening rule results from the interactions of dislocations on the slip systems. Meanwhile, a modified nonlinear kinematic hardening rule and a rate-dependent flow rule at the slip system level are employed to improve the predictive capability of the model for ratchetting deformation. The predictive ability of the developed model to uniaxial and multiaxial ratchetting in macroscopic scale is verified by comparing with the experimental results of polycrystalline 316L stainless steel. The ratchetting in intra-granular scale which is obviously dependent on the crystallographic orientation and stress levels can be reasonably predicted by the proposed model.