Low Stored Energy Research Articles

Evolution of microstructure and mechanical properties of warm-rolled W[sbnd]10Re alloy during annealing at 1500 °C

W10Re alloy is preferred for computed tomography anodes with high molar heat capacity. The deformed W10Re alloy will undergo recrystallization and grain growth during service, resulting in reduced mechanical properties, thermal shock resistance, and service life. The aim of this work is to study the microstructure of the warm-rolled W10Re alloy, its evolution of microstructure and mechanical properties after annealing at 1500 °C. During annealing at 1500 °C, recrystallization and growth of the deformed grain occurred with a latent period. The characteristics of deformed grains in the as-rolled alloy and the variation of kernel average misorientation (KAM) and geometrically necessary dislocations (GND) densities during recrystallization are discussed in detail. In high-temperature annealing, lower stored energy can allow the recrystallization behavior to have a latent period, and the residual deformation of the grain can be retained for a long time. In elevated temperatures, the deterioration of the mechanical properties of the alloy is initially evidenced by a notable decline in strength. This is subsequently followed by the loss of plasticity, which occurs as a result of the further degradation of the structure.

Influence of annealing treatment on grain growth, texture and magnetic properties of a selective laser melted Fe-6.5 wt% Si alloy

The high-density Fe-6.5 wt% Si soft magnetic alloy samples were prepared using selective laser melting (SLM) technology. Annealing treatments with different temperatures were employed to promote grain growth. The microstructure, texture and magnetic hysteresis loops were characterized, aiming to investigate the relationship between microstructure and magnetic properties. The as-printed Fe-6.5 wt% Si alloy had weak texture and low density of ordered phases, and was featured by coarse grains in the top-view section and columnar grains in the side-view section. After annealing at 800 °C–1000 °C, the textures were slightly weakened, while the grain growth was not significant. Increasing the annealing temperature to 1100 °C led to abnormal grain growth behaviors. The grains of the as-printed Fe-6.5 wt% Si alloy showed randomly abnormal growth behaviors rather than oriented growth, which may be related to the low stored energy and initial size advantage before annealing. After annealed at 1100 °C for 1 h, the abnormal grain growth and the formation of large Goss ({110}<001>) and Cube ({100}<001>) grains resulted in microstructure coarsening and texture optimization. Thus, the corresponding ring-shaped sample exhibited excellent magnetic performance. The magnetic induction B8 is 1.21 T, the maximum relative permeability is 14.71 × 103 and the core loss P10/50 is 11.69 W/kg.

To the question of construction of welding inverter sources with a high power factor

Purpose. Design a power-factor-corrected, energy- and cost-efficient switchmode power supply for welding. Methodology. It is proposed to use the principle of direct conversion and to develop the "hybrid" power circuit consisting of a main power path using direct conversion and an auxiliary power path having a converter with an intermediate DC link with relatively low stored energy. Since a load to the welding power supply is the welding arc, its instantaneous power fluctuations during the mains voltage period essentially do not influence the welding process due to the thermal constant of the weld pool molten metal. Effective use of this features of the welding arc allows to optimize the power processing, reduce the amount of energy stored in the reactive elements of the circuit and improve the economical, mass and dimensional parameters of the supplies. Findings. A new power factor corrected switchmode power supply topology is proposed utilizing beforementioned principles of power processing. The algorithm for calculating the switching frequency of supply power switches is given. To confirm the adequacy of the developed provisions, an experimental sample of the power supply was created. Oscillograms of mains voltage and source current consumption and oscillograms in output current limitation mode are obtained. The results of experiments showed that the supply has a power factor &gt; 0.94 in a wide range of powers. Originality. A distinctive feature of the supply is the absence of additional inductive components in the power path, a lower capacitance of the DC-link bulk capacitor and a simplified scheme for limiting its inrush current during initial charging. The supply has an increased open circuit voltage, independent of the mains voltage, which allows for easy arc ignition during manual arc welding. Practical value. Due to the increased power factor, the current drawn from the mains is 30 % to 45 % lower than that of widespread inverter supplies without a power factor corrector. These features allow to simultaneously use more power supply units with the same mains current load, and/or to provide stable welding in conditions of a "weak" mains.

Exceptional thermal stability of additively manufactured CoCrFeMnNi high-entropy alloy with cellular dislocation structures

CoCrFeMnNi high-entropy alloy (HEA) was additively manufactured (AM) by laser powder-bed fusion (L-PBF). The AM CoCrFeMnNi has prominent cellular dislocation structures with a small number of Mn-rich oxides. The thermal stability of the AM CoCrFeMnNi was investigated by isochronal annealing treatment at various temperatures from 400 to 1300 °C for 1 h. Microstructural analysis shows slow dislocation recovery, retarded recrystallization process, and precipitation of additional Cr-Mn based oxides during thermal annealing, resulting in exceptional thermal stability and retained high hardness at elevated temperatures. By thermodynamic calculations, a low stored energy of 1.31 MJ/m3 and a high activation energy of 353 kJ/mol for recrystallization were estimated for the AM CoCrFeMnNi. The exceptional thermal stability of the AM CoCrFeMnNi HEA is mechanistically attributed to the low crystallographic misorientations across the dislocation cell walls, sluggish atomic diffusion, and the pinning effects of the oxide nanoprecipitates.

Fast Quench Propagation Conductor for Protecting Canted Cos-Theta Magnets

Canted Cos-Theta (CCT) magnet design offers remarkable advantages such as a low number of parts and the ability to intercept with the formers the Lorenz forces acting on the windings. However, by principle, it is very challenging to design a self-protected CCT magnet, even with relatively low stored energy and conductor current density. This is predominantly due to the normal zone being unable to propagate along the magnet axial direction. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fast Quench Propagation Conductors (FQPCs) for quench protection of CCT magnets are proposed and studied. FQPC is a superconducting conductor carrying the magnet transport current and placed along the main axis of the CCT magnet in good thermal contact with the turns of the windings. FQPC is connected electrically in series with the CCT windings but electrically insulated at the thermal contacts by the electric insulation of the conductors. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">The FQPCs aim to spread the normal zones in the CCT windings via a shorter axial path rather than only the path along CCT conductors and between them in the formers channels. Typically, ribs of the former inhibit axial quench propagation, and the FQPCs thermally connect CCT windings in the axial direction. The FQPCs quench due to the heat generated in the quenched turn and then act effectively like quench heaters powered by the magnet current. It means a completely passive system powered by the magnet energy that becomes inactive after magnet current decay. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Quench protection transients are calculated using a consecutive-simulation approach involving two software tools developed as part of the STEAM framework at CERN: a finite element (FE) based tool called FiQuS coupled with a finite difference (FD) based tool called LEDET. This approach allows for a three-dimensional (3D) quench simulation and introduces a great level of geometrical detail while maintaining a reasonable computational effort. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">The benefits of the FQPCs depend on their number, placement, and duration of quench transient, which is affected by the CCT magnet size. These dependencies are studied in terms of the winding maximum temperature and voltage-to-ground that result from single, hot-spot-induced quenches in various locations in the windings.

Double Dual High Step-Up Power Converter with Reduced Stored Energy

This paper introduces a dual-switchhigh step-up DC-DC power converter. The proposed converter features a high step-up voltage gain, relatively low cumulative stored energy over its inductors, low voltage stress on the active switches, and high efficiency, even at a relatively high duty ratio. An assessment of the proposed converter against conventional boost and a high step-up power converter is presented in terms of steady-state time, voltage gain, stored energy over its inductors, and efficiency. The assessment shows a reduction of 81.25% and 62.5% of stored energy in inductors to comply with the same operational conditions. Simulation and experimental results are provided to validate the benefits of the proposed dual-switch high step-up power converter.

Enhanced {100} Recrystallization Texture in Strip‐Cast Nonoriented Electrical Steel by Two‐Stage Annealing

Herein, nonoriented electrical steel with enhanced {100} texture is prepared by two‐stage annealing, i.e., prerecovery annealing and then recrystallization annealing. The impact of the annealing process on microstructure, texture, and magnetic properties is investigated using optical microscopy, electron backscattered diffraction, and X‐ray diffraction. It is found that the large {100} deformed matrix with low stored energy begins to recrystallize after the matrix with high stored energy (such as shear bands) is completely recrystallized. Strong Cube and Goss ({110}&lt;001&gt;) texture is developed in the final sheet after conventional annealing. The introduction of prerecovery annealing decreases the stored energy of deformed microstructure and then retarders the start of recrystallization. The final annealed sheet subjected to prerecovery annealing exhibits enhanced multicomponent {100} recrystallization texture containing Cube and {001}&lt;120&gt;–{001}&lt;130&gt; and {001}&lt;110&gt; components. The volume fraction of {100} texture is increased to 22.7–33.6%. It can be attributed to the fact that the prerecovery annealing promotes the growth of new {100} grains recrystallized in the deformed matrix with low stored energy and activates the extended recovery behavior of {001}&lt;110&gt; deformed grains. This improvement of {100} recrystallization texture significantly increases the magnetic induction at the 45° direction and reduces the magnetic anisotropy.

Simulation of strain induced abnormal grain growth in aluminum alloy by coupling crystal plasticity and phase field methods

A mesoscale modeling methodology is proposed to predict the strain induced abnormal grain growth in the annealing process of deformed aluminum alloys. Firstly, crystal plasticity finite element (CPFE) analysis is performed to calculate dislocation density and stored deformation energy distribution during the plastic deformation. A modified phase field (PF) model is then established by extending the continuum field method to consider both stored energy and local interface curvature as driving forces of grain boundary migration. An interpolation mapping approach is adopted to transfer the stored energy distribution from CPFE to PF efficiently. This modified PF model is implemented to a hypothetical bicrystal firstly for verification and then the coupled CPFE-PF framework is further applied to simulating the 2D synthetic polycrystalline microstructure evolution in annealing process of deformed AA3102 aluminum alloy. Results show that the nuclei with low stored energy embedded within deformed matrix tend to grow up, and abnormal large grains occur when the deformation is close to the critical plastic strain, attributing to the limited number of recrystallized nuclei and inhomogeneity of the stored energy.

Avoiding cracks in additively manufactured non-weldable directionally solidified Ni-based superalloys

Additive manufacturing of directionally solidified Ni-based superalloys faces at least two critical obstacles, namely, the formation of stray equiaxed grains and the susceptibility to cracking; circumventing both of these simultaneously is considered difficult. In this study, a comparative study of a non-weldable superalloy IN738 fabricated through the laser directed energy deposition (DED) without preheating the base plate and the electron beam powder bed fusion (EB-PBF) with preheating up to the upper bound of ductility dip temperature range was performed. With appropriate process parameters, a steep and unidirectional temperature gradient, a sufficiently high cooling rate at the liquid/solid interface, and a relatively low cooling rate at the γ′ solvus are obtained simultaneously in the EB-PBF process. The prevalence of these conditions results in the growth of well-aligned columnar dendrites, mitigates the elemental segregation, reduces the built-in microscopic defects, and lowers the stored deformation energy. Consequently, cracking is successfully prevented and reasonable room temperature tensile properties are achieved in the as-printed EB-PBF product. Moreover, recrystallization is not triggered during the post-printing heat treatment, and thus the <001> fiber texture is preserved. This study provides a detailed understanding of the critical factors that need to overcome for producing directionally solidified superalloys through additive manufacturing. • Non-weldable IN738 superalloys was successfully fabricated by EB-PBF with preheating up to the upper bound of DTR. • A steep and unidirectional temperature gradient permits the directional growth of columnar dendrite. • High cooling rates during solidification suppress element segregation and low cooling rates at γ′ solvus help avoid cracks. • The as-printed EB-PBF product with a low stored deformation energy exhibits an excellent resistance to recrystallization.

Quadratic improved super-boost (ISB) converter with low stored energy in components

This article proposes a quadratic boost converter that requires small components compared to the traditional quadratic boost converter. The proposed converter is based on the recently proposed Improved Super-Boost (ISB) converter, and it is driven with a particular pulse width modulation technique (PWM). This allows producing a small switching ripple (input current and output voltage) with a relatively small value of inductors and capacitors. One of the main advantages of the proposed converter is the significant voltage gain, which is equal to the traditional quadratic boost converter; the other advantage is the small size of the components. The proposed converter contains more passive components, but their size is smaller. A comparative evaluation focused on the stored energy was performed; it is demonstrated that the proposed converter requires 50% of the stored energy in inductors and 14% of the stored energy in capacitors for a particular conversion with design specifications.

Topological aspects of mean-field crystallographically resolved models

It is well-known that the crystallographic texture of a polycrystalline aggregate can be represented by the Orientation Distribution Function (ODF). A similar statistical approach can be extended to other microstructural state variables that are of relevance in the context of obtaining microstructurally based and quantitatively accurate structure-properties relations. In principle such statistical representations are of a non-topological nature, in contrast to an RVE (Representative Volume Element) description of the microstructure. However, by including additional variables to the statistical descriptor specific features of the topology may be taken into account. In this paper the example will be shown on how the plastic anisotropy simulation of a conventional deep drawing grade of Interstitial Free (IF) steel can be improved by considering the crystallographic misorientation of pairs of neighboring crystals, which represent the basic structural units of the 2-point mean field ALAMEL crystal plasticity model. In another example it will be shown how the recrystallization texture of the same deep drawing IF steel can be modelled with improved accuracy if the Strain Induced Boundary Mechanism (SIBM) is taken into account whereby a crystal orientation of low stored energy grows into a neighboring orientation of high stored energy.

Role of Hot Rolling in Microstructure and Texture Development of Strip Cast Non-Oriented Electrical Steel

In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate reduction, such as the 20% used in this study, increases the shear bands and {100} deformed microstructure in the cold roll sheet. As a result, in our study, enhanced η and Cube recrystallization texture and the improved magnetic induction were obtained. However, hot rolling with excessive reduction (36–52%) decreased the shear bands and increased the α-oriented deformation microstructure with low stored energy. It enhanced the α recrystallization texture and weakened the η texture, resulting in a decrease in the magnetic induction. In addition, hot rolling promoted the precipitation of supersaturated solid solution elements in the as-cast strip, thereby affecting the subsequent microstructure evolution and the optimization of its magnetic properties.

Disparity in recrystallization of α- & γ-fibers and its impact on Cube texture formation in non-oriented electrical steel

An investigation into the recovery and recrystallization of the two major texture fibres, namely α and γ, during annealing yielded subtle differences between the two. It is reported that with thermal activation static recovery occurs, where dislocation free sub-grains are formed and tend to grow, coalesce, or bulge out. This can form new strain-free recrystallisation nuclei, with the coalescence or bulging phenomenon depending on stored energy and geometrically dislocation density (GND). Due to low lattice curvature or otherwise, it was found α-fiber has low stored energy and GND values which favours bulging into neighbouring deformed grains as opposed to subgrain coalescence. In contrast, γ-fiber tends to undergo rapid subgrain coalescence due to high lattice curvature, i.e., GND and stored energy. The newly formed grains from both texture fibers were also found to typically differ in size, as γ-fiber has a much higher nucleation rate with rapid subgrain coalescence. Furthermore, it was discovered that Cube texture component though nucleating in higher rates within α-fiber, nucleates in all regions of high dislocation densities but will only survive in regions with low recovery and nucleation rates, typically α-fiber. Moreover, Goss texture component was found to preferentially nucleate from γ-fiber.

Structural, electrical, and thermal features of polyimide composites filled with semiconductive MXene sheets

Polymer-based dielectrics are widely applied in the fields of electronics and electrical power systems due to the high breakdown strength, excellent flexibility, and unique self-healing capability. However, the low stored energy density and unsatisfactory heat management of polymer dielectrics hinder the development of polymer-based film capacitors. In this research, artificial composites with improved capacitive energy storage and thermal conductivity are fabricated by blending the two-dimensional semiconductive MXene sheets with a polyimide (PI) matrix. Remarkably, a PI based composite with 1 wt. % MXene sheets increases its dielectric permittivity from ≈3.27 to ≈3.53 and enhances its discharged energy density from ≈1.93 to ≈2.38 J/cm3 while maintaining its low dielectric loss of &amp;lt;0.02 and relatively high charge–discharge efficiency of &amp;gt;80%. Meanwhile, a high in-plane thermal conductivity of 0.418 W m−1 K−1 is achieved for PI/MXene composites with 5 wt. % MXene. In addition, the distribution of temperature field inside the composites has been investigated by a finite element method. These results represent a strategy in polymer dielectrics to achieve simultaneous high energy density and thermal conductivity, which may also have potential for applications in high temperature environments.

Isotope dependence of the type I ELMy H-mode pedestal in JET-ILW hydrogen and deuterium plasmas

The pedestal structure, edge transport and linear MHD stability have been analyzed in a series of JET with the ITER-like wall hydrogen (H) and deuterium (D) type I ELMy H-mode plasmas. The pedestal pressure is typically higher in D than in H at the same input power and gas rate, with the difference mainly due to lower density in H than in D (Maggi et al (JET Contributors) 2018 Plasma Phys. Control. Fusion 60 014045). A power balance analysis of the pedestal has shown that higher inter-ELM separatrix loss power is required in H than in D to maintain a similar pedestal top pressure. This is qualitatively consistent with a set of interpretative EDGE2D-EIRENE simulations for H and D plasmas, showing that higher edge particle and heat transport coefficients are needed in H than in D to match the experimental profiles. It has also been concluded that the difference in neutral penetration between H and D leads only to minor changes in the upstream density profiles and with trends opposite to experimental observations. This implies that neutral penetration has a minor role in setting the difference between H and D pedestals, but higher ELM and/or inter-ELM transport are likely to be the main players. The interpretative EDGE2D-EIRENE simulations, with simultaneous upstream and outer divertor target profile constraints, have indicated higher separatrix electron temperature in H than in D for a pair of discharges at low fueling gas rate and similar stored energy (which required higher input power in H than in D at the same gas rate). The isotope dependence of linear MHD pedestal stability has been found to be small, but if a higher separatrix temperature is considered in H than in D, this could lead to destabilization of peeling-ballooning modes and shrinking of the stability boundary, qualitatively consistent with the reduced pedestal confinement in H.

The Origin of the Cube ({001}) Texture in Non-oriented Electrical Steel Sheets

Although cube ({001}<100>) is a preferred final texture in non-oriented electrical steel (NOES) sheets, this texture is rarely produced in commercial NOES products. The major texture of fully processed NOES is usually the unfavorable <111>//ND (normal direction) fibre, which originates from the deformed <111>//ND texture. To reduce/eliminate the <111>//ND texture and promote the cube texture, one method is to change the initial texture before cold rolling. In this research, two electrical steels containing 0.88 wt% and 2.8 wt% Si are cold rolled with the initial textures rotated by 60° around the ND before cold rolling. This rotation leads to the rotated Goss ({110}<110>) texture in the deformed microstructure. Within the shear bands of the rotated Goss grains, crystallites with cube orientation are formed. Regions of these crystallites may have lower stored energy than their neighboring areas. During annealing, these crystallites preferentially nucleate and grow, and form a strong cube texture in the final steel sheets.

Microstructural evolution and grain growth mechanism of pre-twinned magnesium alloy during annealing

Abstract The microstructural evolution and underlying grain growth mechanism of a {10–12}-twin-containing Mg alloy during annealing are investigated through quasi in situ electron backscatter diffraction measurements of a rolled AZ31 alloy subjected to precompression along the rolling direction (RD). The precompressed material shows a partially twinned structure consisting of a twinned region and a residual matrix region, and this structure changes to an almost twin-free structure consisting of grown grains with serrated grain boundaries in twin- and matrix-originated regions after annealing at 250 °C for 1 h. In addition, the average grain size almost doubles and the internal strain energy decreases significantly after annealing. These microstructural variations are induced mainly by grain growth through the strain-induced migration of high-angle grain boundaries without the movement of twin boundaries. The twinned region of the precompressed material has higher stored strain energy than the residual matrix region because the crystallographic orientation of the former region is favorable for basal slip and because of the occurrence of the dislocation transmutation reaction in the twins. For reducing the total strain energy accumulated in the precompressed material, the residual matrix region—having lower stored strain energy—preferentially grows while consuming the twinned regions formed in the surrounding grains during annealing. As a result, the area fraction of grains with a matrix texture increases whereas that of grains with a twin texture decreases after annealing. The twin texture intensity increases significantly and this texture becomes more concentrated along the RD because the highly RD oriented twins tend to grow during annealing on account of their fairly low stored strain energy.

Severe warm-rolling mediated microstructure and texture of equiatomic CoCrFeMnNi high entropy alloy: A comparison with cold-rolling

The effect of severe warm-rolling on the microstructure and texture development in FCC equiatomic CoCrFeMnNi HEA was investigated in the present work. For this purpose, the HEA was warm-rolled to 90% reduction in thickness at 600 °C and annealed for 1 h at temperatures up to 1200 °C. To highlight the effect of warm-rolling, a critical comparison was made with similarly deformed and annealed cold-rolled HEA. The warm-rolled HEA showed an ultrafine lamellar microstructure, which was, however, significantly coarser than the cold-rolled HEA. The significantly coarser microstructure in the warm-rolled HEA could be attributed to the dynamic annihilation of dislocations during deformation. Warm-rolled HEA showed a pure metal or copper type texture instead of a predominantly brass type texture in the cold-rolled HEA. The stark differences in the deformation texture could be attributed to the increase in the SFE at the temperature of warm-rolling, which promoted more homogeneous deformation by dislocation slip over twin mediated deformation and extensive shear band formation. The lower stored energy and coarser deformation structure of the warm-rolled HEA resulted in higher recrystallization temperature, and consistently larger recrystallized grain size than the cold-rolled HEA. Annealing also resulted in the weakening of the recrystallization texture owing to the absence of strong preferential nucleation or growth. The HEA warm-rolled and annealed at 750 °C resulted in a fine-grained, completely recrystallized microstructure with the optimum strength-ductility combination. The present results revealed that warm-rolling could be effectively used as a processing route for tailoring microstructure and properties of CoCrFeMnNi HEA.

Thermomechanical Processing Map in Retaining {100}//ND texture via Strain-Induced Boundary Migration Recrystallization Mechanism

The feasibility of establishing thermomechanical conditions to promote {100}//ND fiber texture via strain-induced boundary migration (SIBM) recrystallization mechanism in a non-grain oriented (NGO) electrical steel was investigated. Single-hit uniaxial compression at various temperatures and strains has been applied on Fe-6 wt pct Si to establish the relationship between stored energy and the softening mechanisms. Recovery only and recrystallization by SIBM or by subgrain growth (SGG) have been observed depending on the stored energy level. A strong {100}//ND fiber recrystallization texture, i.e., 45 pct area fraction, was seen in the sample which was deformed to 0.2 strain at 650 °C and then annealed at 1000 °C for 15 minutes, whereas only 13 pct {100}//ND fiber component was observed after 0.4 strain at 500 °C followed by the same annealing treatment. By examining the same microstructural region before and after annealing via EBSD, it has been shown that {100}//ND textured recrystallized grains were formed adjacent to the {100}// ND textured deformed matrix. Low stored energy has been shown to favor the formation of {100}//ND texture recrystallized grains via SIBM recrystallization mechanism attributed to its slow recrystallization nucleation rate. The results from the deformation studies have been used to suggest a processing window map concept to define the recovery, SIBM, and SGG regions for the starting as-cast columnar microstructure.

Formation mechanism and evolution of surface coarse grains on a ZK60 Mg profile extruded by a porthole die

Porthole die extrusion of Mg alloys was studied by means of experimental and numerical studies. Results indicated that an inhomogeneous microstructure formed on the cross-section of the extruded profile. On the profile surface, abnormal coarse grains with an orientation of <11−20> in parallel to ED (extrusion direction) appeared. In the profile center, the welding zone was composed of fine grains with an average size of 4.19 μm and an orientation of <10−10> in parallel to ED, while the matrix zone exhibited a bimodal grain structure. Disk-like, near-spherical and rod-like precipitates were observed, and the number density of those features was lower on the profile surface than that in the profile center. Then, the formation and evolution of coarse grains on the profile surface were investigated, which were found to depend on the competition between static recrystallization and grain growth. The stored deformation energy was the factor dominating the surface structure through effective regulation over nucleation of the precipitates and recrystallization. A profile with a low stored deformation energy suppressed formation of precipitates and consequently facilitated grain growth rather than recrystallization, resulting in the formation of abnormal coarse grains. Finally, the surface coarse grains contributed detrimentally to hardness, tensile properties, and wear performance of the bulk structure.