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The cold-rolled NiTi alloy was treated by electropulsing and muffle furnace at the same temperature for minutes, respectively. In order to find the difference between two methods for the recrystallization of the NiTi alloy, the hardness, electrical resistivity and microstructure of the NiTi alloy were investigated. The hardness and microstructure evolution of NiTi alloy indicates that electropulsing can reduce the recrystallization temperature of NiTi alloy by 200 °C owing to the enhancement of atom diffusion. Compared with the traditional heat treatment, electropulsing can easily refines grain of the NiTi alloy with an average size of about 41 nm, due to increases of the nucleation rate and limited grain growth. In addition, electropulsing can decrease resistivity of NiTi alloy to the minimum value at the low frequency of electropulsing for 2.5 min. For NiTi alloy treated by furnace annealing at 300 and 350 °C, the phase transition from martensite to austenite induces the hardness increase with increasing temperature and prolonging time. [ABSTRACT FROM AUTHOR]

The recrystallized microstructure and texture of AZ31 Mg alloy after rapid thermal annealing (RTA) was investigated. A mathematical model of RTA temperature of AZ31 Mg alloy was established based on the thermal equilibrium theory. The two double-peak textures with basal poles tilted 5–10° away from the normal direction towards the rolling direction or towards the transverse direction were formed in the AZ31 alloy during RTA. The tilted basal texture was originated from recrystallized grains formed along grain boundaries for the low rolling reduction or recrystallized grains formed within the shear bands and twins for the high rolling reduction. During RTA, the recrystallization mechanism was sensitive to the previous rolling reduction and the annealing temperature, and the mechanisms of the microstructure and texture evolution of the AZ31 alloy during RTA were discussed. [ABSTRACT FROM AUTHOR]

Electropulsing treatment (EPT) has been first applied to the recrystallization of a refractory metal—tungsten (W). We have three major observations: (i) the recrystallization temperature of a rolled pure W under EPT is ∼900 K higher than its conventional recrystallization temperature (1603 K); (ii) the time required for recrystallization is significantly reduced compared with that of conventional heat treatment (CHT); (iii) the recrystallized grains are also much finer than the ones under CHT. Based on quantitative analysis, we conclude that the huge increase of the recrystallization temperature of the rolled pure W under EPT is due to the high heating rate generated by EPT and high activation energy for vacancy diffusion of W, and the accelerated recrystallization and grain refinement have resulted from the coupling of thermal and electromigration effects of EPT at relatively high temperatures. [ABSTRACT FROM PUBLISHER]

Abstract: Electropulsing induced recrystallization of a cold-rolled Mg–9Al–1Zn alloy was studied using electron backscattering diffraction pattern (EBSD), transmission electron microscopy (TEM) and hardness test. The results indicated that compared with conventional heat treatment, electropulsing treatment (EPT) substantially accelerated recrystallization of the cold-rolled Mg–9Al–1Zn alloy within a short time of several seconds at relatively low temperature, as well as suppressed precipitation of β-Mg17Al12 phase. Based on the EPT enhanced atomic diffusion resulting from the coupling of the thermal and athermal effects with the direct electron–atom interactions, EPT accelerated recrystallization due to significantly increasing both the velocity of dislocation motion and subgrain growth rate. [Copyright &y& Elsevier]

Abstract: Influences of electropulsing treatment (EPT) on microstructure and mechanical properties of cold-rolled Mg–9Al–1Zn alloy strip were studied. EPT was found to accelerate the recrystallization of cold-rolled Mg–9Al–1Zn alloy strip at a relatively low temperature, and obtain fine microstructure of quasi-single-phase-recrystallized grains. The EPT-induced microstructural changes weakened the intensity of the basal fiber texture, and increased elongation to failure remarkably with a decrease in tensile strength. Fracture surface analysis showed that transition from intergranular brittle facture to transgranular dimple fracture took place with an increase in frequency of EPT. The rapid recrystallization behaviour of the Mg–9Al–1Zn alloy strip under EPT was attributed to the enhancement of nucleation rate and atomic diffusion resulting from the coupling of the thermal and athermal effects. It is supposed that EPT can provide a highly efficient method for the intermediate-softening annealing of magnesium alloys sheet/strips. [Copyright &y& Elsevier]

Abstract: The effect of electropulsing treatment (EPT) on the microstructure and texture evolution of the cold-rolled AZ91 magnesium alloy strip was investigated using X-ray diffraction (XRD) and electron backscattered diffraction patterns (EBSD). The results indicated that EPT accelerated tremendously the recrystallization behaviour of the cold-rolled AZ91 magnesium alloy strip at a relatively low temperature within a short time of 7s. It also suppressed precipitation of β-Mg17Al12 phase, compared with conventional heat treatment. The recrystallized grains favourably weakened the intensity of the basal texture. A mechanism for rapid recrystallization process during EPT was proposed based on the enhancement of nucleation rate and atomic diffusion resulting from the coupling of the themal and athermal effects. [Copyright &y& Elsevier]

Recrystallization annealing is a necessary process for refining the grain of processed metallic materials and eliminating work hardening. However, it can cause a large amount of precipitation and coarsening of the second phase in supersaturated solid solution alloys, which is detrimental to the subsequent processing and aging processes aimed at controlling the precipitation phase. This article compared the effects of electropulsing (EPT) and conventional heat treatment (CHT) processes on the microstructure and mechanical properties of cold-rolled Cu-3.5Ti alloy. The results indicated that compared with CHT, EPT achieved full recrystallization of the alloy at a lower temperature (650 °C, 100 °C lower than CHT) and in a shorter time (10 s, 1/360 of CHT), and effectively inhibited the precipitation of β-Cu 4 Ti phase, resulting in a fine and uniform supersaturated solid solution. This process significantly improved both the strength and plasticity of the alloy. The yield strength, tensile strength and elongation to failure of the EPT-650 °C/10 s sample were 570 MPa, 598 MPa and 21.2 %, respectively, which were 27.8 %, 25.9 % and 19.1 % higher than those of the CHT-750 °C/1 h sample. EPT significantly increased the recrystallization nucleation rate of the alloy, while its rapid heating method inhibited the precipitation of β-Cu 4 Ti phase, ensuring the recrystallization process was not affected by the precipitated phase, which was the main reason for rapid recrystallization and grain refinement of Cu-3.5Ti alloy by EPT at lower temperatures and shorter time. • Compared with CHT, EPT achieved full recrystallization of Cu-3.5Ti alloy at a lower temperature and in a much shorter time. • Compared with CHT, EPT significantly enhanced both the strength and plasticity of the Cu-3.5Ti alloy. • EPT reduced the thermodynamic energy barrier of nucleation, suppressed discontinuous phases, forming finer grains. • EPT is a new toughening heat treatment process for metallic materials, with high efficiency and low energy consumption. [ABSTRACT FROM AUTHOR]

The influence of the electropulsing parameters including the current density and the frequency, on the rolling force, the microstructure and the mechanical properties of AZ31 strips processed by electroplastic rolling (EPR) were investigated in this study. On the basis, the double grain refinement mechanism, combing the rapid completed static recrystallization refinement (SRX) of AZ31 strip before the roll with the subsequent dynamic recrystallization refinement (DRX) of AZ31 strips at the deformed zone, was put forward in the whole process of EPR. According to the mechanism of double grain refinement, an innovative method of the production of AZ31 ultrathin strip with excellent comprehensive properties is established and verified. The AZ31 ultrathin strip with the thickness of 0.35 mm was obtained at the optimal electropulsing parameters, and the total reduction of 69% can be obtained though only 2 continuous passes without any off-line intermediate heat treatment in the process of EPR; besides, the maximum rolling temperature does not exceed 483 K. It is indicated that the technology of EPR with the high current density of the electropulsing is one of the most potential method to improve the plastic formability of hardly-deformed metals. [ABSTRACT FROM AUTHOR]

Recrystallization and micronizationof camptothecin (CPT), a potentanticancer agent, has been performed using the supercritical antisolvent(SAS) process in this study. The effect of different solvents on themorphology, mass median diameter (Dp50), particle sizedistribution (PSD) and the crystallinity of obtained CPT microparticleswas investigated in detail. Five pure solvents, acetic acid, dimethylformamide,chloroform, N-methyl-2-pyrrolidone, dimethyl sulfoxide(DMSO), and a series of solvent mixture of ethanol/DMSO with differentvolume ratios (R), where Rwas definedas the ethanol volume to total solvent volume, were selected as solvents.The raw CPT and processed CPT particles were characterized using SEM,laser diffraction particle size analysis, FT-IR spectroscopy, LC–MS,powder XRD, and DSC. The processed CPT microparticles were flake-likeand much thinner and more uniform than the lamelliform CPT raw material.The Dp50of the processed CPT ranged from 0.39 to 2.14μm, and the PSD of the processed CPT microparticles became muchnarrower. Solvents with a higher ratio of density and viscosity, lowersurface tension, and lower solvation power will form smaller CPT microparticleswith lower crystallinity, which helps to improve the solubility ofCPT in biological liquids. Furthermore, the addition of ethanol intoDMSO improves the properties of DMSO and decreases the CPT solubility,which is beneficial to the acquisition of smaller particles, and theparticle size decreased significantly with the increase of R. The chemical structure and crystalline structure of CPTdid not change after the SAS process. However, the crystallinity ofthe obtained CPT microparticles was less than that of raw CPT, andvaried for different solvents. [ABSTRACT FROM AUTHOR]

Abstract: Thermo-electropulsing rolling process (TER), a novel technique by combining the methods of electropulsing with warm rolling process, was created to manufacture AZ31 magnesium alloy strips, and the effects of both warm rolling process (WR) and TER on mechanical properties and microstructure of AZ31 magnesium were also studied and compared in the current study. The results indicated that WR tended to decrease the elongation to failure of the samples compared with that of the raw sample, while TER tended to increase the elongation. With an increase in the pass reduction, the elongation of samples under WR decreased, while that of TER increased. During WR, only twins were induced in the AZ31 alloy, while TER substantially induced recrystallization (DRX). The coupling of the thermal and athermal effects in electropulsing tended to accelerate the movement of the dislocation and the diffusion of the vacancy, which facilitated to the completion of DRX at a relatively low temperature under TER. [Copyright &y& Elsevier]

Abstract: The effect of electropulsing tension (ET) on the elongation to failure, microstructure and fracture behavior of Mg–3Al–1Zn (AZ31) alloy was investigated. It was found that electropulsing increased the plasticity significantly at a high strain rate of 2.5×10−2 s−1 and the mechanism was based on dynamic recrystallization (DRX). The calculated temperature of the ET sample indicated that ET dramatically accelerated DRX at a relatively lower temperature, compared with conventional warm deformation. Based on the flux of vacancies contributed by the thermal and electromigration effects of ET, a model for simulating DRX under ET was established. The interplay between the two effects and a comparison with conventional warm deformation were also discussed. [Copyright &y& Elsevier]

Abstract: The effect of electropulsing treatment (ET) on the microstructure of Mg–3Al–1Zn (AZ31) alloy was investigated. Combing with the calculated temperature of the sample after ET, it was found that electropulsing accelerated dynamic recrystallization (DRX) at a relatively low temperature and a high strain rate. Based on the interplay between the accumulation and annihilation effects of electropulsing, a tentative mechanism of DRX induced by electropulsing was discussed. [Copyright &y& Elsevier]

Abstract: The microstructural evolution in cold rolled AZ31 magnesium alloy during electropulsing treatment (EPT) is analyzed by texture analysis. The recrystallization mechanism during electropulsing is found to depend on the previous amount of reduction. The recrystallized grains give rise to the tilted basal texture by a rotation of 45°–60° from the rolling direction (RD) towards the normal direction (ND). The mechanism of the microstuctural evolution during electropulsing is discussed from the point of view of grain boundary motion. [Copyright &y& Elsevier]

Abstract: The effect of electropulsing tension (ET) on the elongation to failure and microstructure of Mg–3Al–1Zn (AZ31) alloy was studied. It was found that electropulsing increased the elongation to failure dramatically at a high strain rate of 2.5×10−2 s−1, compared with the non-ET sample. The mechanism for increasing the elongation was proposed mainly based on dynamic recrystallization (DRX). The results in this investigation indicated that an ideal improvement in plasticity and fine equiaxial grains were obtained at a low temperature and a high strain rate due to the coupling of the thermal and athermal effects of ET. It is different from conventional theories. [Copyright &y& Elsevier]

Recrystallization and micronization of 9-nitro-camptothecin (9-NC) has been investigated using the supercritical anti-solvent (SAS) technology in this study. Five operating factors, i.e., the type of organic solvent, the concentration of 9-NC in the solution, the flow rate of 9-NC solution, the precipitation pressure and the temperature, were optimized using a selected OA 16 (4 5 ) orthogonal array design and a series of characterizations were performed for all samples. The results showed that the processed 9-NC particles exhibited smaller particle size and narrower particle size distribution as compared with 9-NC raw material (Form I), and the optimum micronization conditions for preparing 9-NC with minimum particle size were determined by variance analysis, where the solvent plays the most important role in the formation and transformation of polymorphs. Three new polymorphic forms (Form II, III and IV) of 9-NC, which present different physicochemical properties, were generated after the SAS process. The predicted structures of the 9-NC crystals, which were consistent with the experiments, were performed from their experimental XRD data by the direct space approach using the Reflex module of Materials Studio. Meanwhile, the optimal sample (Form III) was proved to have higher cytotoxicity against the cancer cells, which suggested the therapeutic efficacy of 9-NC is polymorph-dependent. [ABSTRACT FROM AUTHOR]