Route Bc Research Articles

Conjoint influence of equal channel angular pressing and annealing on microstructure and mechanical properties of aluminum alloy 7075

AbstractThe effect of equal channel angular pressing combined with inter‐pass and post‐process annealing on the microstructure and mechanical properties of the Al‐7075 alloy has been studied. The samples underwent successful equal channel angular pressing for three passes using the Bc route. The most significant changes in mechanical properties were observed after the first pass. Despite an 88 % reduction in grain size, the hardness of the alloy increased by 45 % and the fracture toughness decreased by 75 %. Post‐process annealing was found to be an effective method for enhancing the alloy‘s toughness. Annealing the one‐pass sample at 310 °C resulted in a 33 % increase in fracture toughness; from 15.8 J to 21.02 J. Inter‐pass annealing had a lesser impact on improving fracture toughness compared to post‐process annealing. It can be concluded that a balanced combination of strength and toughness can be achieved by utilizing a combination of equal channel angular pressing and inter‐pass or post‐process annealing. Examination of the fracture surfaces of the samples revealed intragranular fractures, with the annealed samples exhibiting higher energy absorption during impact and better toughness compared to the non‐annealed sample.

Influence of Equal Channel Angular Pressing Processing on the Microstructure, Hardness and Corrosion Resistance of Al-Si Alloy

In this study, the impact of heat treatment and Equal Channel Angular Pressing (ECAP) processing routes on refining the microstructure, hardness, and corrosion resistance of Al-7.5% S alloy in a 3.5% NaCl solution was examined. The alloy underwent T5 and T6 heat treatments, followed by ECAP processing via routes A and Bc in a mold with a channel angle of 120° at room temperature. The results indicate that dendritic α-Al grains transformed to globular and fiber shapes after processing routes Bc and A, respectively. Both processing routes fragmented coarse and brittle Si particles into smaller sizes in the eutectic phase. The use of a combination of heat treatment and the Equal Channel Angular Pressing (ECAP) process significantly improved the hardness and corrosion resistance of the samples. The hardness of the heat-treated samples increased considerably from 68 to 116 and 129 HV after three and four passes, respectively. Reducing the area ratio between the noble silicon particles and the less noble eutectic aluminum phase greatly enhances the resistance of alloy to pitting corrosion.

Investigating the role of fine grain structure on mineral deposition and resistance to corrosion initiated mechanical failure of the fine grained AZ31 magnesium alloy

ABSTRACT In the present work, fine grained AZ31 magnesium (Mg) alloy was produced by equal channel angular pressing (ECAP) and exposed to simulated physiological conditions to investigate the role of refined microstructure on biomineralisation, degradation and corrosion initiated mechanical failure. ECAP was carried out at 200°C in Bc route for up to four passes (one complete cycle) and a grain refinement up to 1.9 ± 1.1 μm was achieved in AZ31 Mg alloy from a starting size of 36 ± 4.1 μm. X-ray diffraction (XRD) analysis confirms the development of non-basal texture in the ECAPed AZ31 alloy. The phases deposited on the surface of the samples after immersion carried out in simulated physiological environment were analysed by XRD and scanning electron microscopy which confirms the higher level of mineral phase deposition on ECAPed AZ31 alloy due to increased surface energy (39.11 ± 2.1 mJ/cm2) compared with base alloy (20.5 ± 5.3 mJ/cm2). Higher tensile strength (169.9 ± 5.5 MPa) was observed for the fine grained AZ31 Mg alloy compared with the base alloy (120.5 ± 3.7 MPa) to resist the corrosion initiated mechanical failure after exposing the samples to corroding simulated physiological environment for 1 day.

A comparative study of machine learning and response surface methodologies for optimizing wear parameters of ECAP-processed ZX30 alloy

Magnesium, valued for its lightweight, recyclability, and biocompatibility, faces challenges like its poor wear behavior and mechanical properties that limit its adaptation for a multitude of applications. In this study, various statistical analyses, and machine learning (ML) techniques were employed to optimize equal channel angular pressing (ECAP) process parameters for improving the wear behavior of Mg-3wt.% Zn-0.7 wt% Ca alloy. ECAP was conducted up to four passes via route Bc at 250 °C. Wear testing of both as-annealed (AA) and ECAP-processed alloys was performed using the dry ball-on-flat wear method under varying loads, speeds, and time. One pass (1P) and 4Bc-ECAP resulted in a notable uniform grain refinement of 86 % and 91 %, respectively, compared to the AA. X-ray diffraction (XRD) analysis confirmed a refined structure attributed to extensive dynamic recrystallization. Mechanical wear testing revealed a significant reduction in volume loss (VL), up to 56 % and 28.5 % after 1P and 4Bc samples, respectively, compared to the AA sample, supported by the observed texture intensity. The coefficient of friction (COF) stabilizes at 0.30–0.45, indicating low friction characteristics. Next, by adjusting wear load and speed through design of experiments (DOE), the wear output responses, VL and COF, were experimentally investigated. The output responses were predicted in the second step using ML, 3D response surface plots, and statistical analysis of variance (ANOVA). According to the regression model, the minimal VL was attained at a 5 N applied load. Also, the wear speed and VL at different passes are inversely proportional. On the other hand, the optimal COF was obtained at applied load about 2–3 N and 250 mm/s at different passes. The wear process variables were then optimized using different optimization techniques namely, genetic algorithm (GA), hybrid DOE–GA, and multi-objective genetic algorithm (MOGA) approaches.

Optimization of ECAP parameters of ZX30 alloy using feature engineering assisted machine learning and response surface approaches

The precise control of equal channel angular pressing (ECAP) deformation parameters is crucial for producing ultrafine grains in structural ZX30-Mg alloy biodegradable components. To address this challenge, this study aims to conduct a comprehensive analysis of the effects of various ECAP parameters on the microstructure, corrosion, and mechanical properties of ZX30 alloy. ZX30 was utilized through a maximum of 4 passes along routes A, Bc, and C, using die angles of 90ᵒ and 120ᵒ, by utilizing machine learning (ML), artificial neural networks (ANNW), response surface methodology (RSM), and simulated annealing (SA) techniques. Experimental investigations revealed the significance of the number of passes in reducing grain size by up to 1.9 µm, consequently enhancing both mechanical and corrosion resistance properties, notably in route Bc. The corrosion rate was enhanced by 97.6 % while the corrosion resistance was increased by 254 % compared to the as-annealed condition. RSM and simulated annealing optimization results closely aligned with experimental findings. The evaluation of each extrusion parameter revealed that the correlation coefficient, as determined by the optimized Gaussian Process Regression model, ranged from 94 % to 97 % for all evaluated responses, and near to unity via ANNW. The overall distribution of mechanical and corrosion measures showed a significant correlation with the number of passes, with route A, Bc, and die angle following closely behind. Interestingly, route Bc had the main impact on the yield strength, followed by the number of passes and die angle. Thus, the combination of statistically and mathematically selected techniques effectively promotes the attainment of optimal properties. Furthermore, the Simulated Annealing (SA) algorithm demonstrated its capability to provide optimal solutions for ECAP deformation parameters. This study presents a promising avenue for improving the accuracy of ECAP-induced structural optimization in ZX30 alloy.

Effect of equal channel angular pressing on strain deformation behavior of ultrafine grained during low temperature superplasticity of AA5083

AA5083 with ultrafine grain structure was produced through equal channel angular pressing using different levels of ECAP tensions, underwent a series of tensile tests. The superplasticity temperature 573 K at low temperatures. This study investigate how varying the ECAP strain influences the distinctive microstructure of the alloy and its impact on deformation mechanisms within the low-temperature superplasticity range. A fraction of the high angle borders increased when the equal channel angular pressing strain was increased from 1 to 2, while the sub-grain size stayed nearly same. This was the most applicable microstructural evolution. After double passes, the material showed superplastic elongations, but after single pass, it did not show low temperature superplasticity. Upon analyzing the mechanical data using typical deformation mechanisms, it was determined that dislocation climb controlled the samples deformation after the first pass, whereas grain boundary sliding was responsible for the sample's low temperature superplasticity after the second pass. In the present study, we explored the differences in deformation mechanisms by considering the microstructures formed under various ECAP strains. Equal channel angular pressing with a BC route and an effective strain of 1∼2, we created an ultrafine-grained AA5083. A significant increase was seen in the fraction of particles measuring 1.8–3.8 μm under the current ECAP conditions. The implementation of equal channel angular pressing, there was a significant increase in the occurrence of voids with sizes ranging from 0.8 to 1.8 μm. According to the current analysis and results, if moderate superplastic elongation is guaranteed, it may be preferable to have fewer equal channel angular pressing passes than those that result in the largest elongation while taking into account cavitation damage and the low temperature superplasticity of ultrafine grained AA5083 used in commercial applications.

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.

On some Features of the Grain and Subgrain Size in a Cu-Cr-Zr Alloy After ECAP Processing and Aging

A Cu-1Cr-0.1Zr alloy has been subjected to ECAP processing via route Bc and aging at 250-800°C. Electron BackScatter diffraction (EBSD), Transmission Electron Microscopy (TEM) and X-Ray Diffraction Line Profile Analysis (XRDLPA) techniques have been used to unveil some peculiarities of the grain and subgrain structure with a special emphasis on the comparison of the grain size estimated by the three techniques. For the alloy ECAP processed and aged up to 16 passes, the grain size (from EBSD, 0.2 < d < 5 μm), subgrain size (from TEM, d ~ 0.75 μm) and “apparent” average crystallite size (from XRDLPA, d < 0.25 μm) are manifestly different. The results were compared to the published data and analyzed based on the fundamental aspects of these techniques.

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.

Effect of microstructural and texture evolution of ECAP-processed Mg-Zn-Zr alloy on the corrosion and wear behaviours for bone repair applications

Mg-Zn-Zr alloys show great potential for replacing the currently used materials in biodegradable applications. They exhibit similar mechanical properties to that of human bones, while possessing favorable biodegradable properties that can be engineered to allow the complete, safe degradation of the alloy in the human body around the time the bones fully heal, without the need for a removal surgery. Literature confirms that grain refinement through processing via severe plastic deformation (SPD) techniques enhances both corrosion and wear behavior of Mg alloys; thus, in this study Mg-3Zn-0.6 Zr (ZK30) billets were ECAP-processed for up to 4-passes of route Bc to investigate their wear and corrosion behaviors improvement in relation to their microstructural and texture evolutions. Electron back-scatter diffraction (EBSD) was used to study microstructural and texture evolution of the billets, their electrochemical behavior was investigated using a body simulated fluid as a corrosive agent, and wear tests with load, velocity and distance parameters were carried out to investigate the improvements resulting from the produced ultrafine-grained structure and crystallographic texture. EBSD revealed that 4-pass ECAP processing yielded a grain size reduction of 92.7%. Accordingly, this ultrafine-grained structure reduced the corrosion rate by 94%, improved the corrosion resistance by 726%, and notably improved the billets’ wear behavior, compared to the as-annealed condition. Therefore, this in-depth analysis confirms the promising potential of ZK30 alloy for industrial use in bone applications.

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.

Improved corrosion resistance and mechanical properties of severely deformed ZM31 alloy

The hexagonal close-packed (HCP) crystal structure of Mg alloys lead to poor formability as well as other undesirable mechanical behaviors in an otherwise highly sought-after alloy for commercial use. This study investigates the evolution of microstructure, texture, corrosion and mechanical behaviors in Mg–Zn–Mn (ZM31) alloy after processing using Equal Channel Angular Pressing (ECAP). Dynamic recrystallization was evident in the ECAP-processed samples, correlated with a substantial fiber structure, and resulted in the attainment of notable grain refinement and high lattice strain. Average grain sizes of 2.2 and 2 μm were achieved via 2 and 4-Pass Bc processing, respectively. This significant refinement yielded lower corrosion rates through enhancement of the thickness, coherency, and stability of formed protective oxide layers. The corrosion rate in the NaCl medium was substantially enhanced by 99.5% after four passes via route Bc. The recrystallized fine structure was found to have contributed to yield strength, ultimate strength, and microhardness improvements. Deformation enhanced yield and ultimate strengths by 132% and 64%, respectively. The distinctive grain refinement mechanism exhibited through the current ECAP procedure has potential to pave the way for novel and impactful utilizations of ZM31 in industries that demand exceptional mechanical and corrosion performance.

Investigating the role of processing temperature on the microstructure evolution, mechanical properties, and corrosion behaviour of equal channel angular pressed AZ31 Mg alloy

AZ31 magnesium (Mg) alloy was subjected to equal channel angular pressing (ECAP) through Bc route at three different temperatures (200, 250 and 300 °C) to investigate the role of processing temperature on the microstructure evolution. All the sample were processed for one complete cycle which includes 4 consecutive pressings. Workpiece processed at 200 °C has shown relatively higher grain refinement (2.1 ± 1.4 μm) compared with the samples processed at 250 °C (5.6 ± 2.7 μm) and 300 °C (7 ± 5.5 μm) from a starting size of 36 ± 4.1 μm. Increased hardness was measured for the ECAPed samples at 200 °C due to the higher level of grain refinement. Workpiece produced at 200 °C exhibited higher tensile strength (270.9 ± 6.3 MPa) compared with the other processed samples and base alloy. Surface energy measurements from the contact angles show the positive effect of grain refinement on increasing the hydrophilic nature of AZ31 alloy. Corrosion experiments from the potentiodynamic polarization studies demonstrate lower corrosion current for the base alloy compared with all of the processed alloys. The deteriorated corrosion performance in the ECAPed alloys can be claimed to the increased crystal imperfections due to ECAP. From the results, it is understood that the lower processing temperatures are preferable to achieve higher level of grain refinement in ECAP of AZ31 Mg alloy. Excellent mechanical properties can be achieved in AZ31 alloy by ECAP and the decreased corrosion resistance is a concern to pay more attention.

Effect of ECAP by Route BC and Aging Heat Treatment on the Structure and Properties of Cu0.4Cr0.3Zr Alloy

Effect of ECAP by Route BC and Aging Heat Treatment on the Structure and Properties of Cu0.4Cr0.3Zr Alloy

Grain growth activation energy of ECAP-processed Mg-Ce alloy: Effect of deformation temperature

In the present work, the grain growth activation energy, Q was evaluated in a Mg-0.3Ce (wt%) alloy after equal-channel angular pressing (ECAP) processing via route Bc for 4 passes at 300 and 350 °C and followed by isochronal annealing at 150, 250, 350, and 450 °C for 2 h. The results demonstrated that Q depends strongly on the deformation processing. The Q value was equal to 111.4 ± 5.7 kJ/mol for the sample ECAP-processed at 300 °C. While the sample ECAP-processed at 350 °C shows the presence of two different Q values depending on the annealing temperature, QI = 26.5 ± 3.4 kJ/mol in the low-temperature range (150–350 °C) and QII = 120.7 kJ/mol in the high-temperature range (350–450 °C). This behaviour was attributed to the resulting deformation microstructure and the occurrence of dynamic grain growth during ECAP processing at 350 °C.

Superplastic behavior of a fine-grained Mg−Gd−Y−Ag alloy processed by equal channel angular pressing

An extruded Mg−6Gd−3Y−1.5Ag (wt%) alloy was processed by 6 passes of equal channel angular pressing (ECAP) at 553 K using route Bc to refine the microstructure. Electron back-scattered diffraction (EBSD) analysis showed a fully recrystallized microstructure for the extruded alloy with a mean grain size of 8.6 µm. The microstructure of the ECAP-processed alloy was uniformly refined through dynamic recrystallization (DRX). This microstructure contained fine grains with an average size of 1.3 µm, a high fraction of high angle grain boundaries (HAGBs), and nano-sized Mg5Gd-type particles at the boundaries of the DRXed grains, detected by transmission electron microscopy (TEM). High-temperature shear punch testing (SPT) was used to evaluate the superplastic behavior of both the extruded and ECAP-processed alloys by measuring the strain rate sensitivity (SRS) index (m-value). While the highest m-value for the extruded alloy was measured to be 0.24 at 673 K, the ECAP-processed alloy exhibited much higher m-values of 0.41 and 0.52 at 598 and 623 K, respectively, delineating the occurrence of superplastic flow. Based on the calculated average activation energy of 118 kJ mol−1 and m-values close to 0.5, the deformation mechanism for superplastic flow at the temperatures of 598 and 623 K for the ECAP-processed alloys was recognized to be grain boundary sliding (GBS) assisted by grain boundary diffusion.

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.

A review on impact route process on AA5083 of back pressure through equal channel angular pressing

The goal of this research is to reduce the back-pressure needed to press throughout all channels. Equal Channel Angular Pressing has acted upon in a single pass at various temperature effects and with varying back pressure. To find result of specimens for investigating a back-pressure fracture. AA5083 samples were analyzed using an optical microscope to observe microstructural resulting from equal channel angular pressing. Hardness and tensile test data are used to analyzed mechanical behaviour. The microstructural characteristics, such as dislocation density, micro-strain, and crystallite size, are studied from the XRD peak profiles using a modified and distinct technique. The ideal processing parameter combination to press crack-free AA5083 through an equal channel is temperature of 220 °C and back pressure of 170 N/mm2. The processing of AA5083 using Equal Channel Angular Pressing under an assault of heated conditions and up to four passes of back pressure using various techniques has successful. According to the processing method and the number of passes, the microstructural, mechanical, and wear behaviour has been studied. After being subjected to the Equal Channel Angular Pressing process, the samples showed a significant degree of grain refinement as well as improved mechanical and wear resistance qualities. The mixed fracture mode, which is ductile and brittle, has validated by the fractographs of the tensile samples. The study of the X-ray line profiles shows that the enhanced mechanical properties are a result of changes made to the microstructure during equal channel angular pressing. It’s streamlined microstructure and greater microhardness, the sample produced using route BC displays superior mechanical and wear properties.[copyright information to be updated in production process]

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.

The Impact of ECAP Parameters on the Structural and Mechanical Behavior of Pure Mg: A Combination of Experimental and Machine Learning Approaches

Commercial pure Mg specimens were processed through equal channel angular pressing (ECAP) using two dies with die angles of 90° and 120°. Mg billets were processed up to four passes via different route types. Machine learning (ML) techniques were adopted to estimate the ECAP parameters and verify the experimental findings. Several ML techniques were employed to estimate the effect ECAP parameters of pure Mg on microstructural evolution, Vicker’s microhardness (HV), and tensile properties for ECAP billets and their as-annealed (AA) counterparts. Electron back-scatter diffraction (EBSD) was applied to determine the structural evolution and crystallographic texture both prior to and following the ECAP process for the Mg billets. EBSD analysis showed that route Bc is the most effective route in grain refinement, and four passes of route Bc experienced a significant refinement of 86% compared to the AA condition. Furthermore, the crystallographic texture showed that four passes of route Bc produced the most robust texture that was greater than 26.21 times random. ML findings revealed that the grain size demonstrated a strong correlation of −0.67 with rising number of passes, while ϕ affected the grain size strongly with 0.83. When adopting a 90°-die to accumulate the plastic strain up to 4Bc, the subsequent HV was indeed 111% higher than that of the AA equivalent. From ML findings it was clear that the number of passes was the most significant parameter on the Mg HV values, while ECAP channel angle (ϕ) revealed high correlation factor with HV values as well. Furthermore, four passes of route Bc with ϕ = 90° and 120° led to a significant increase of the tensile strength by 44.7%% and 35.7%, respectively, compared to the AA counterpart. ML findings revealed that the tensile strength was affected by the increasing number of passes with a strong correlation of 0.81, while affecting ductility moderately with 0.47.