Equal Channel Angular Pressing Passes Research Articles

In-situ synchrotron diffraction analysis of deformation mechanisms in an AA5083 sheet metal processed by modified equal-channel angular pressing

Severe plastic deformation (SPD) is a process to significantly improve the mechanical properties of materials by grain refinement. For forming at room temperature (RT), higher strengths can thus be achieved; for increased temperatures (HT), greater elongations can be achieved. This great potential has been chiefly applied only on laboratory scale due to a lack of industrial process design. Equal-channel angular pressing (ECAP) offers the possibility to integrate these advantages in industrial processes. This paper investigates a modified ECAP process for aluminum AA5083 sheet metal. Two passes of ECAP for sheet metal and an additional heat treatment were used. To study the material deformation on a micro-scale, in-situ synchrotron measurements at DESY (Hamburg) were performed to analyze the evolution of lattice strains and dislocation densities during tensile testing. The mechanical properties of the ECAP-processed sheet material reveal an increase in yield strength and a decrease in elongation at RT. Higher strains can be measured for the processed material at elevated test temperatures. In-situ diffraction results show a changed behavior of the ECAP sheet material compared to the reference material for both temperature regimes. These changes are based on the increased defect density in the material, which leads to increased strength at RT. At HT, dynamic recrystallization occurs during tensile testing, and the prevailing deformation mechanisms reconfigure. Electron backscatter diffraction (EBSD) and micrographs are used to interpret and supplement the observations. The findings provide the basis for the in-depth understanding of the deformation behavior of the material and help to apply the ECAP process on an industrial scale.

Effect of equal channel angular pressing on magnesium alloys − A review

Magnesium (Mg) alloys own excellent properties that includes better castability, low density and great specific strength. Mg and its alloys are easily available and economical. Necessity of Mg and its alloys for manufacturing and engineering purposes has increased, predominantly in the area of aircraft and automobile applications. The known limitation of magnesium is its poor formability at room temperature, with inadequate slip systems due to hexagonal closed packed construction of magnesium. Formability of magnesium alloys will be enhanced at room temperature by grain structure refinement which improves ductility with grain refined structure. Severe plastic deformation (SPD) procedure induces extreme strain within the sample to produce ultrafine grained structure. Additionally, few shortcomings of magnesium is increased wear mass loss and corrosion rate obstructing the use of Mg and its alloys in several industrial appliances. Wear resistance and corrosion behaviour can be enhanced by SPD thereby increasing the requirement of magnesium alloys for engineering applications. Among SPD, equal channel angular pressing (ECAP) is an efficient approach to develop and vary the mechanical and microstructural properties as per the need. In ECAP approach, the workpiece undergoes shear deformation and large strains are induced in the workpiece with no variation in cross sectional aspect of the workpiece. Microstructure plays a very important role in achieving the required mechanical properties. ECAP process creates ultrafine-grained microstructure with different number of ECAP passes with varying temperatures inducing high strain rate.

Optimization of wear parameters for ECAP-processed ZK30 alloy using response surface and machine learning approaches: a comparative study

The present research applies different statistical analysis and machine learning (ML) approaches to predict and optimize the processing parameters on the wear behavior of ZK30 alloy processed through equal channel angular pressing (ECAP) technique. Firstly, The ECAPed ZK30 billets have been examined at as-annealed (AA), 1-pass, and 4-passes of route Bc (4Bc). Then, the wear output responses in terms of volume loss (VL) and coefficient of friction (COF) have been experimentally investigated by varying load pressure (P) and speed (V) using design of experiments (DOE). In the second step, statistical analysis of variance (ANOVA), 3D response surface plots, and ML have been employed to predict the output responses. Subsequently, genetic algorithm (GA), hybrid DOE–GA, and multi-objective genetic algorithm techniques have been used to optimize the input variables. The experimental results of ECAP process reveal a significant reduction in the average grain size by 92.7% as it processed through 4Bc compared to AA counterpart. Furthermore, 4Bc exhibited a significant improvement in the VL by 99.8% compared to AA counterpart. Both regression and ML prediction models establish a significant correlation between the projected and the actual data, indicating that the experimental and predicted values agreed exceptionally well. The minimal VL at different ECAP passes was obtained at the highest condition of the wear test. Also, the minimal COF for all ECAP passes was obtained at maximum wear load. However, the optimal speed in the wear process decreased with the number of billets passes for minimum COF. The validation of predicted ML models and VL regression under different wear conditions have an accuracy range of 70–99.7%, respectively.

Effect of Zinc and Severe Plastic Deformation on Mechanical Properties of AZ61 Magnesium Alloy.

This study investigates the effects of zinc (4 wt.%) and severe plastic deformation on the mechanical properties of AZ61 magnesium alloy through the stir-casting process. Severe plastic deformation (Equal Channel Angular Pressing (ECAP)) has been performed followed by T4 heat treatment. The microstructural examinations revealed that the addition of 4 wt.% Zn enhances the uniform distribution of β-phase, contributing to a more uniformly corroded surface in corrosive environments. Additionally, dynamic recrystallization (DRX) significantly reduces the grain size of as-cast alloys after undergoing ECAP. The attained mechanical properties demonstrate that after a single ECAP pass, AZ61 + 4 wt.% Zn alloy exhibits the highest yield strength (YS), ultimate compression strength (UCS), and hardness. This research highlights the promising potential of AZ61 + 4 wt.% Zn alloy for enhanced mechanical and corrosion-resistant properties, offering valuable insights for applications in diverse engineering fields.

Refractory High‐Entropy Alloys Produced from Elemental Powders by Severe Plastic Deformation

A comparative investigation of two fundamentally different approaches for the synthesis, microstructure evolution, and mechanical properties of the refractory high‐entropy alloys (RHEA) HfNbTaTiZr and HfNbTiZr is performed. The two methods comprises conventional arc (button) melting and a powder route based on mechanical alloying and consolidation via severe plastic deformation. In particular, blended elemental powder is pre‐compacted and subjected to one or four passes of equal channel angular pressing (ECAP) at 500 °C and then 10 revolutions of high pressure torsion (HPT) at room temperature to an effective strain between 4 and 40. Some samples are then annealed at 500 °C for 1 h to investigate the thermal stability of the phases. The four ECAP passes at 500 °C do not result in the formation of the body‐centered cubic (BCC) phase typical for the program RHEAs despite the presence of interfacial zones between particles and defect‐driven diffusion. Nevertheless, a single ECAP pass is sufficient to create a solid bulk sample for subsequent HPT. After 10 HPT revolutions, in contrast to melting route resulting in a single BCC phase alloy, both alloys form new phases comprising a Nb‐rich BCC phase and a ZrHf‐rich HCP phase in both alloys.

Microstructure and properties of biodegradable Zn-0.8Mn-0.5Cu-0.2Sr alloys processed by ECAP

In recent years, Zn alloys had been regarded as biomedical materials with good biocompatibility and biodegradability. However, the mechanical properties of Zn alloys were often not sufficient for the ideal orthopedic internal fixation implant. In order to improve the comprehensive mechanical properties of Zn alloys by strengthening and toughening, equal channel angular pressing (ECAP) method and Bc route were applied to process Zn-0.8Mn-0.5Cu-0.2 Sr alloys. Meanwhile, the effects of multi-pass ECAP on mechanical properties, corrosion behavior and microstructure were systematically investigated. As a result, ECAP could significantly refine the grain sizes of the as-cast Zn-0.8Mn-0.5Cu-0.2 Sr alloys. Only after 2 passes, the average grain sizes of the Zn-0.8Mn-0.5Cu-0.2 Sr alloy could be refined from 54.04 μm in as-cast to 1.20 ± 0.76 μm. In addition, the increase of ECAP passes promoted the precipitation of MnZn13 phase and reduced texture strength, which affected the strength and ductility. The UTS of the 2 P and 4 P alloys were 337.6 MPa and 320.4 MPa, respectively. And as ECAP passes increased from 2 to 8, the EL gradually increased from 24.9% to 46.3%. After ECAP, the corrosion rates of the Zn-0.8Mn-0.5Cu-0.2 Sr alloys increased. The corrosion rates of the 2 P and 4 P alloys measured by the weight loss method were about 0.022 mm/year and 0.019 mm/year. Thus, Zn-0.8Mn-0.5Cu-0.2 Sr alloy was expected to be a promising biodegradable material. Meanwhile, ECAP could be an effective avenue to achieve high comprehensive mechanical properties and suitable corrosion rates.

Enhanced superplasticity of ultrafine-grained WEQ612 magnesium alloy via the coupling effect of grain boundary segregation and dense precipitation

Achieving low-temperature, high-strain-rate (LTHSR) superplasticity is important for preparing rare-earth (RE)–Mg alloy products with complex shapes. Herein, an ultrafine-grained Mg–6.22Y–0.98Er–2.11Ag (wt%, WEQ612) alloy was prepared via equal-channel angular pressing (ECAP). After 16 passes of ECAP and aging at 473 K for 58 h, an average grain size of 600 nm was achieved, and there was a high density of intergranular precipitates with an average size of approximately 180 nm. The WEQ612 alloy exhibited excellent superplasticity during superplastic deformation, with elongations of 451% at 523 K and 1 × 10−4 s−1, and 834% at 573 K and 1 × 10−2 s−1. The high density of intergranular precipitates, which were uniformly distributed at the grain boundaries, promoted dynamic recrystallization (DRX) during superplastic deformation and inhibited grain growth. The grain boundary co-segregation of Y and Ag further improved the grain boundary stability of the alloy. Despite the general consensus that grain boundary sliding (GBS) is the main mechanism of superplasticity, a more complex role of GBS and DRX was identified in this study. The identified mechanism provides a reference for GBS and grain boundary rotation as well as dislocation motion during superplastic deformation, and helps to describe the intermediate processes that occur during superplastic deformation. Thus, this study provides insights into the development of LTHSR superplastic RE–Mg alloys.

Mechanical properties and microstructure of Al–Mg (5052) alloy processed by equal-channel angular pressing (ECAP) with variation of ECAP routes and heat treatment

Equal-Channel Angular Pressing (ECAP) has become an effective technique of severe plastic deformation designed to produce ultrafine grain metals with improved mechanical properties, such as a good combination of strength and ductility. A report on the effect of ECAP routes on the mechanical and microstructure of commercial 5052 aluminum alloy needs also to be included. This work has been undertaken, in order to obtain the results. In this work, several deformation routes were used to process the Al – Mg (5052) alloy, namely A, Ba, Bc and C. Deformation route A involved repeatedly pushing the sample into the ECAP die without rotation, route Ba was performed by rotating the sample through 90° in alternate directions between each pass, route Bc by rotating the sample 90° in the same sense between each pass and route C by rotating the sample 180° between passes. The addition of the pass number decreases the grain size of ECAP-processed samples when compared to the as-annealed sample. It also confirmed that the microstructure of the 8-pass samples shows a finer grain size than the as-annealed sample. Furthermore, the Bc route (samples rotated in the same sense by 90° between each pass) has been proven to be the most effective deformation route, in order to obtain equiaxed ultrafine grain structure when compared to other deformation routes. This phenomenon takes place due to the continuous deformation in all cubic planes. The restoration after the 4-pass number will lead to the rapid evolution of sub-grains to high-angle grain boundaries, forming equiaxed grains. The characterization of the hardness number also shows that the addition of the ECAP pass number increases the hardness number of 5052 aluminum alloy, where samples processed with the Bc route indicate the highest hardness number at 168.4 HB. Moreover, a similar phenomenon also suggests that the tensile strength of all ECAP deformation routes has comparable values. The effect of heat treatment for samples with the Bc route also shows that 200 °C annealed samples have the highest hardness number and tensile strength when compared to other samples.

Effect of number of ECAP passes on structure and mechanical properties of Al–Ca–Mn–Fe alloy

The effect of number of equal-channel angular pressing (ECAP) passes on the structure and mechanical properties of the as-cast 4% Ca–1.3% Fe–0.8% Mn–0.1% Zr–0.1% Sc Al alloy is studied. ECAP was carried out at room temperature, through BC path using an angle between the channels of 110°. The number of ECAP passes was N = 2, 3, and 4. The as-cast alloy consisted of the solid solution dendrites (Al) and the [(Al) + Al10CaFe2 + Al4Ca] eutectic, as well as of a small fraction of the Al6(Fe, Mn) particles. As a result of ECAP, the dendrites are elongated approximately at an angle of 30° relative to the direction of ECAP. After two passes of ECAP, the dislocation density increased, but with an increase in the number of passes, the dislocation density slightly decreased as a result of the rearrangement of the dislocation structure; besides calcium segregated from the eutectic. After ECAP, a significant hardening of the alloy was observed. The highest strength observed after two passes (the ultimate tensile strength of the as-cast alloy was 130 MPa, and after the second pass it was 305 MPa), and the lowest one was after four passes (the ultimate strength was 219 MPa). The relative elongation of the ECAP-processed samples did not depend on the number of passes and it was about 1%.

Microstructure evolution and mechanical properties of Mg–Mn–RE alloy processed by equal channel angular pressing

Equal Channel Angular Pressing (ECAP) has been used to successfully produce ultrafine-grained ME21 alloy with a good strength-ductility synergy. The microstructure of the as-cast ME21 alloy and its evolution during the ECAP processing were characterized using a combination of optical microscopy (OM) and scanning electron microscopy (SEM). Fracture surfaces after tensile test were also characterized using SEM. Chemical analysis and phase identification were done by energy dispersive spectroscopy (EDS) and X-ray diffraction analysis, respectively. The combination of these techniques enabled the interpretation of the mechanical behavior during the various processing stages of the alloys. The ECAP process was performed up to 16 passes, producing a uniform ultra-fine grain (1 µm) ME21 alloy resulting from full dynamic recrystallization. At room temperature, the yield strength after 16 ECAP passes (191.4 MPa) was 251% higher than that of the as-cast ME21 alloy, accompanied by a good elongation of 8.1%. The hardness increased to 60.7HV which is about 52% higher than that of the as-cast alloy. These improvement in mechanical properties is due to the ultra-fine grains with high angle grain boundaries (HAGBs) and the precipitate strengthening effects of the uniformly dispersed fine precipitates of Mg12Ce and Mn formed as a result of the intense shear during the ECAP process.

Processing of the Ti25Ta25Nb3Sn Experimental Alloy Using ECAP Process for Biomedical Applications

The development of titanium-β alloys for biomedical applications is associated with the addition of alloying elements or the use of processing techniques to obtain suitable bulk properties. The Ti25Ta25Nb3Sn alloy has been highlighted for its mechanical properties and biocompatibility. To further enhance the properties of titanium alloys for biomedical applications, equal channel angular pressing (ECAP) was used due to its capability of refining the microstructure of the alloy, leading to improved mechanical properties without significant changes in Young’s modulus. This study aims to evaluate the impact of ECAP on the microstructure of the Ti-25Sn-25Nb-3Nb alloy and investigate the correlation between the microstructure, mechanical properties, and corrosive behavior. Grain refinement was achieved after four ECAP passes, with an average grain diameter of 395 nm and a non-homogeneous structure, and microhardness was slightly increased from 193 to 212 HV after four ECAP passes. The thermomechanical aspects of the ECAP processing have led to the formation of a metastable α″ phase during the first two passes, while after four passes, the structure was composed only of the β phase. The corrosion resistance of the alloy was increased after four passes, presenting the best results in terms of the improvement of passivation corrosion density.

Refining 18R-LPSO phase into sub-micron range by pre-kinking design and its prominent strengthening effect on Mg97Y2Zn1 alloy

In this study, a composite deformation strategy of pre-kinking (equal channel angular pressing (ECAP)) followed by large-ratio hot extrusion (HE) was designed to refine the 18R long period stacking ordered (LPSO) phase into sub-micron range in a Mg97Y2Zn1 (at.%) alloy. After the composite processing, the mechanical properties of the alloy are significantly enhanced, superior to the majority of reported Mg97Y2Zn1 and other LPSO-containing Mg alloys. Among the composite deformed alloys, the 16P-HE alloy exhibits the best mechanical properties with tensile yield strength (TYS) of 475 MPa, ultimate tensile strength (UTS) of 526 MPa, and fracture elongation (FE) of 14.5%. Quantitative analysis of 18R phase indicates that increasing ECAP pass from 1 to 16 gradually decreases the average size of 18R phase from 5.1 µm to 2.3 µm. After HE, the 18R phase is further refined with a corresponding decrease in the average size in the descending order of 1P-HE (4.3 µm), 4P-HE (3.2 µm), and 16P-HE (1.4 µm) alloys. Calculation of the strengthening contributions confirms that the superior mechanical properties of 16P-HE alloy are mainly due to its strongest interface strengthening (145 MPa) and grain boundary strengthening (189 MPa) from the sub-micron 18R phase and α-Mg grains. Moreover, the strengthening effect of 18R phase decreases gradually with their morphology changing from particles to fibers, and to blocks. The obtained results further deepen and broaden the strengthening-toughening theory of 18R phase.

Effect of intermediate-temperature severe plastic deformation on microstructure evolution, mechanical properties and corrosion behavior of an Al-Zn-Mg-Cu alloy

Grain refinement is an important means to strengthen the properties of alloy. Here the Al-Zn-Mg-Cu alloy was processed by intermediate-temperature equal channel angular pressing (ECAP) to evaluate the grain refinement, mechanical properties and corrosion resistance of the alloy. Ultra-fine grained structure was obtained by 4 passes ECAP applied to Al-Zn-Mg-Cu alloy. With the increase of ECAP passes, some low angle grain boundaries (LAGBs) transform to high angle grain boundaries (HAGBs), forming micron-sized fine grains. Meanwhile, the strength, microhardness and corrosion resistance of the alloy were improved with the increase of extrusion passes. The pinning effect caused by dynamic precipitation and the mechanical fragmentation caused by ECAP refine the grains of the alloy. The microhardness and strength of the deformed alloy were improved under the combined action of fine grain strengthening, dislocation strengthening and second phase strengthening. A high density of dislocations, refined grains and secondary phases were produced by intermediate-temperature ECAP, which together improved the corrosion resistance of the alloy.

Creep and microstructure stability of different purity aluminium and its alloy processed by ECAP method

Severe plastic deformation (SPD) is a perspective method for preparation of ultrafine-grained materials. A coarse-grained aluminium with different purity and Al-0.2Sc alloy were processed by equal-channel angular pressing (ECAP) to evaluate the effect of severe plastic deformation on the thermal stability of resulting ultrafine-grained (UFG) microstructure and on creep behaviour of the SPD processed samples. These materials were subjected to ECAP up to 8 passes by route BC at room temperature with a die that had an internal angle of 90° between the two parts of the channel. The microstructural investigations were performed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with an electron back-scatter diffraction (EBSD) unit. Tension creep tests in constant load regime were conducted at temperature of 473 K on a both coarse-grained and UFG states of materials. It was found that creep behaviour of aluminium and its alloy is influences by their grain size, stability during creep test, material purity, solid solution and precipitate strengthening and fraction of high-angle grain boundaries development during ECAP process. While creep resistance of pure aluminium at elevated temperatures is improved already after 1 ECAP pass, further ECAP passes lead to degradation of creep life in case of low purity Al and Al-0.2Sc alloy.

Effect of CaO Addition on Microstructural Evolution Due to the Annealing of AZ31 Alloys Processed by Equal-Channel Angular Pressing (ECAP)

This study demonstrated the application of equal-channel angular processing (ECAP), which was performed via the BC route, to determine the effect of the addition of CaO on the microstructural evolution of an AZ31 alloy due to annealing. Compression tests were performed to evaluate the mechanical properties of the alloy, and the corresponding microstructures were observed to elucidate the flow behavior. Ca-bearing second-phase particles were fragmented with the increase in the number of ECAP passes. The increase in the yield strength and flow stress with the addition of CaO was attributed to the dispersion of the Ca-bearing second-phase particles. When the CaO-added AZ31 and commercial AZ31 alloys were subjected to annealing, their flow stress decreased owing to the grain growth. However, the extent of the decrease in the flow stress for the CaO-added AZ31 alloy was lower than that for the commercial AZ31 alloy.

Investigation of Severe Plastic Deformation Effects on Magnesium RZ5 Alloy Sheets Using a Modified Multi-Pass Equal Channel Angular Pressing (ECAP) Technique.

The present study investigates the effects of multiple passes of equal channel angular pressing (ECAP) on magnesium alloy sheets with the assistance of an Inconel plunger along with a die setup having a channel angle of 120° and corner angle of 10° operating at a temperature of 200 °C followed by the required heat treatment processes. The microstructural analysis of the sheet samples at various stages of the multi-pass hot ECAP has shown evidence of ultrafine grain refinement (UFG) due to the occurrence of severe plastic deformation. X-ray diffraction analysis has also exhibited the presence of phases like MgZn and CeZn3 which is supposedly responsible for the enhancement of the mechanical properties. As a result, the room temperature tensile and compressive strengths have improved by 6.12% and 6.63%, respectively, after the second pass, and 11.56% and 15.64%, respectively, after the fourth pass of ECAP. Additionally, the hardness of the sheets has increased by 6.49% and 16.64% after the second and fourth pass of hot ECAP, respectively, mainly attributed to the drastic decrease in grain size from 164 μm to 12 μm within four ECAP passes, all these with a negligible change in ductility. This success in the thermomechanical processing of Mg-RZ5 alloy sheets using a die channel angle of 120° with a minimal number of passes of hot ECAP under a controlled equivalent strain, further opens doors for incorporating optimizations and/or additional aspects so as to achieve even better grain refinements, and consequently, mechanical strength improvements thereby catering to the industrial needs of aerospace and construction areas.

Enhancement of Mechanical Behaviors and Microstructure Evolution of Nano-Nb2O5/AZ31 Composite Processed via Equal-Channel Angular Pressing (ECAP)

The automobile industry uses magnesium for load-bearing components due to its low density, durability, and ductility. This study investigated a nanocomposite containing Nb2O5 (3 and 6 wt%) nanoparticles as reinforcement with AZ31 magnesium alloy made by stir casting. A severe plastic deformation was conducted on the cast samples via equal-channel angular pressing (ECAP) after homogenization at 410 °C for 24 h and aging at 200 °C for 10 h. The microstructural distributions and mechanical properties of the magnesium metal matrix composites (MMCs) reinforced with Nb2O5 nanoparticles were investigated via ECAP. With the increase in the number of ECAP passes, the grain sizes became uniform, and the size of secondary phases reduced in the pure Nb2O5/AZ31 MMC. The grain size decreased remarkably after the ECAP process from 31.95 µm to 18.41µm due to the dynamic recrystallization during plastic deformation. The mechanical properties of hardness, ultimate tensile strength, and elongation effectively improved after each ECAP pass. The maximum values achieved for the Nb2O5/AZ31 composite subjected to ECAP were 64.12 ± 12 HV, 151.2 MPa, and 52.71%.

Effect of equal-channel angular pressing on ordering kinetics and twinning in an 18-carat AuCuAg alloy

The ability to modify microstructural features and the resulting properties of red gold provides an attractive potential for applications in electronics, dental devices or jewelry. In this study, the effect of severe plastic deformation by equal-channel angular pressing (ECAP) on microstructural evolution in an 18-carat AuCuAg alloy, and on the ordering kinetics during subsequent aging, is investigated. Differential scanning calorimetry measurements show that the ordering process is significantly influenced by a plastically deformed microstructure and lattice defects introduced by one or two passes of ECAP. Electron backscatter diffraction and transmission electron microscopy demonstrate that the microstructural evolution during ordering, accompanied by the formation of an L10 superstructure, substantially depends on the thermo-(mechanical) history of the material: While the undeformed material clearly shows a hierarchical structure of twins on different length scales, only a few nanotwins are observed within the strongly deformed microstructures after ECAP. Moreover, after ECAP, static recrystallization is considerably suppressed during long-term annealing at elevated temperatures close to the phase transition temperature. These results clearly highlight the potential of ECAP in combination with heat treatments for microstructural optimization of AuCuAg alloys and their applications.

Simultaneously enhancing mechanical properties and electrical conductivity of Cu-0.5%Cr alloy as 5G connector material

With the rapid development of the 5 G communication, materials such as the high-speed backplane connector and the integrated circuit lead frame require higher strength and electrical conductivity. Copper alloys have been widely concerned due to their excellent electrical conductivity, thermal conductivity and good strength. A new method of preparing the Cu-0.5%Cr alloy by equal channel angular pressing (ECAP), deep cryogenic treatment (DCT) and aging treatment (AT) was proposed. The electrical conductivity, mechanical properties and microstructure of the Cu-0.5%Cr alloy were investigated, and the precipitation kinetics was analyzed. The results show that ECAP deformation and DCT treatment make the grains elongate and refine along the deformation shear direction. After four ECAP passes and DCT (12 h), the lamellar grains with the thickness of 200–300 nm were obtained, and the dislocation density was evidently increased. After the subsequent AT treatment, the fine Cr phase disperses uniformly at the grain boundaries and within the grains, and distributes on the matrix and along the dislocation lines. Compared with the solid solution, the results showed that after four passes of ECAP + DCT (12 h) + AT (425 ℃ × 1 h), the microhardness increased from 60.5 HV to 210 HV, the electrical conductivity changed from 27.9 % IACS to 69 % IACS, the strength improved from 262 MPa to 587 MPa, the elongation to failure decreased from 44.2 % to 21.9 %. The electrical conductivity was enhanced due to the second phase charge analysis showed that the scattering effect on electrons is weakened. The improvement of strength could be attributed to grain refinement and increase of dislocation density. Based on the Avrami empirical equation of precipitation kinetics analysis, the electrical conductivity equation and the phase change kinetics equation were established, and the relationship between aging time and electrical conductivity was established.

Effect of equal channel angular pressing on the mechanical properties of homogenized hybrid AZ61 magnesium composites

This study addressed the development and investigation of an AZ61 hybrid composite (HBC) fabricated by the stir casting method followed by equal channel angular pressing (ECAP). The HBC was reinforced using both Al 2 O 3 and SiC nanoparticles. The microstructural examination showed that the introduced reinforcements broke down the round-like formed precipitates into needle-like shapes that enhanced the ductility. Furthermore, the grain size of the HBCs is highly reduced while increasing the number of ECAP passes due to dynamic recrystallization (DRX). The obtained mechanical properties showed that the optimal yield strength (YS), ultimate tensile strength (UTS), and elongation were observed in the AZ61+2%Al 2 O 3 +1%SiC hybrid composite after two passes of ECAP. The Hall Petch strengthening mechanism was primarily responsible for the improved mechanical properties of AZ61 HBC, jointly with the mutual contribution of several mechanisms, including the coefficient of thermal expansion, Orowan looping, and load transfer mechanisms. • AZ61/Al2O3/SiC hybrid composite was produced by stir casting followed by ECAP. • Due to dynamic recrystallization, grain size was highly reduced during ECAP. • The mechanical characteristics of HBC enhanced after the each ECAP pass.