Elongation Research Articles

Crescimento e nutrição da Urochloa brizantha cv. Marandu inoculada com bactéria promotora de crescimento vegetal e sob diferentes doses de nitrogênio

A demanda por produção de quantidades adequadas de biomassa vegetal é um grande desafio da pecuária brasileira que enfrenta grave situação em relação à degradação da maioria das pastagens nativas ou cultivadas, especialmente em solos deficientes em nutrientes biogênicos como o nitrogênio. O objetivo do presente estudo foi avaliar o crescimento e nutrição de Urochloa brizantha em decorrência da inoculação com Azospirillum brasilense associado com adubação nitrogenada. O experimento foi conduzido em casa de vegetação da Universidade Paranaense – UNIPAR, Umuarama – PR. O delineamento experimental foi inteiramente casualizado, constituído por seis tratamentos (testemunha, inoculado sem N, inoculado + 50 e 75 kg ha-1 N, sem inoculação + 50 e 75 kg ha-1 N) e cinco repetições cada. 10 dias após a semeadura efetuou-se o desbaste das plantas em excesso deixando apenas cinco plantas por vaso. 60 dias após a semeadura, as plantas foram coletadas para análise de massa seca, alongamento foliar e teores de nutrientes foliares. A inoculação resultou em um ganho na massa seca da parte aérea, comprimento de parte aérea e número de perfilhos, porém não houve ganho em massa seca da raiz. Pôde-se observar maior concentração de nitrogênio foliar e índice de clorofila nos tratamentos com maiores concentrações de adubação nitrogenada, inoculado ou não. Portanto, conclui-se que a inoculação com A. brasilense associado à adubação nitrogenada se mostrou um excelente aliado no aumento da produção e no desenvolvimento de U. brizantha cv. Marandu.

Effects of minor Nd and Er additions on the precipitation evolution and dynamic recrystallization behavior of Mg–6.0Zn–0.5Mn alloy

Abstract A new wrought magnesium (Mg) alloy based on Mg–6.0Zn–0.5Mn (ZM60) is developed, which performs excellent combination of high tensile yield strength and good ductility. We investigate the effects of micro-alloying on dynamic precipitation, dynamic recrystallization (DRX) and mechanical properties of ZM60 alloy. The co-addition of minor (0.6 wt%) neodymium (Nd) and (0.3 wt%) erbium (Er) can accelerate the twinning and DRX process of ZM60 alloy at the initial compression deformation stage. The dynamic precipitation process is also accelerated due to Nd and Er co-alloying. Dislocation accumulation disappears and a higher density of rod β 1 ′ precipitates and some thick β 2 ′ precipitates in matrix and fine twins, which inhibits the growth of DRX grains in compressed ZM60–0.6Nd–0.3Er alloy. The as-extruded ZM60–0.6Nd–0.3Er alloy has a yield strength (YS) of 245.8 MPa, ultimate tensile strength (UTS) of 347.2 MPa and elongation (EL) of 16.3%. The yield strength and tensile strength are improved via minor Nd and Er additions due to fine complete DRX grains, second phase particles and high density of precipitates. The grain refinement, weakened reserved working hardening and weakened basal fiber texture improve the elongation of ZM60–0.6Nd–0.3Er alloy.

Desenvolvimento e produtividade de trigo submetido a aplicações aéreas sequenciais de Azospirillum

A cultura (Triticum aestivum) do trigo expressa grande importância como alimento no mundo. Sabendo disso, o aumento da produtividade desta cultura é uma excelente linha de pesquisa, contribuindo para elevar o fornecimento de alimentos. Assim, o objetivo do trabalho foi avaliar o desenvolvimento e produtividade da cultura de trigo com aplicações sequenciais de Azospirillum na cultura do trigo. O experimento foi desenvolvido no município de Guarapuava-PR, na região Centro-Sul do Paraná, com clima Cfb – subtropical mesotérmico úmido, com altitude aproximada de 1120 m. Para a condução do trabalho foi utilizado delineamento experimental de blocos ao acaso com cinco tratamentos sendo eles: Controle absoluto - T1 (sem aplicação foliar de Azospirillum brasilense), aplicação de inoculante Azospirillum brasilense no perfilhamento - T2, aplicação do inoculante no perfilhamento + elongação - T3, aplicação do inoculante no perfilhamento + elongação + emborrachamento - T4, aplicação do inoculante no perfilhamento + elongação + emborrachamento + floração - T5, com 4 repetições, totalizando 20 unidades amostrais. Após a aplicação dos tratamentos foliares, foi realizado as avaliações de: massa total de planta, massa de mil grãos, produtividade, peso hectolitro e altura de planta. A aplicação de Azospirillum brasilense foliar, independente do somatório de épocas de aplicação não apresentou interferência no desenvolvimento da cultura de trigo, assim como não elevou a produtividade da cultura.

Effect of Strain Rate on the Microstructure and Texture Evolution of the ZK60 Alloy Sheets

The dynamic recrystallization (DRX), precipitation and texture evolution of the ZK60 alloy sheets rolled at 300 °C with different strain rates were studied, and the effects of texture on the plasticity were also clarified. The DRX grain sizes at five strain rates (5–25 s−1) are 1.4 μm, 1.2 μm, 1.8 μm, 2.4 μm and 2.8 μm, respectively, while the DRX volume fractions are 35.8%, 75.0%, 82.0%, 88.0% and 93.0%, respectively. The maximum intensity values of the (0002) texture are 7.91, 8.22, 7.64, 5.76 and 5.34 at five strain rates, respectively. The strongest (0002) texture is observed at the strain rate of 10 s−1, which is related to the relatively low DRX volume fraction and the precipitation density. The tensile strength (UTS) and yield strength (YS) increases firstly and then decreases, while the elongation (EL) gradually increases with increasing the strain rate, suggesting that the plasticity of the alloy sheet can be improved by decreasing the basal texture intensity and increasing the dispersion degree of the basal texture. The optimal comprehensive mechanical properties are obtained at the strain rate of 10 s−1, with UTS of 358 MPa, YS of 291 MPa and EL of 21.5%. The DRX grain sizes at five strain rates (5–25 s−1) are 1.4 μm, 1.2 μm, 1.8 μm, 2.4 μm and 2.8 μm, respectively, while the DRX volume fractions are 35.8%, 75.0%, 82.0%, 88.0% and 93.0%, respectively. The maximum intensity values of the (0002) texture are 7.91, 8.22, 7.64, 5.76 and 5.34, respectively. The tensile strength (UTS) and yield strength (YS) increases firstly and then decreases, while the elongation (EL) gradually increases with increasing the strain rate, and the optimal comprehensive mechanical properties are obtained at 10 s−1, with UTS of 358 MPa, YS of 291 MPa and EL of 21.5%

Online prediction of mechanical properties of hot rolled steel plate using machine learning

In industrial steel plate production, process parameters and steel grade composition significantly influence the microstructure and mechanical properties of the steel produced. But determining the exact relationship between process parameters and mechanical properties is a challenging process. This work aimed to devise a deep learning model, to predict mechanical properties of industrial steel plate including yield strength (YS), ultimate tensile strength (UTS), elongation (EL), and impact energy (Akv); based on the process parameters as well as composition of raw steel, and apply it online to a real steel manufacturing plant. An optimal deep neural network (DNN) model was formulated with 27 inputs parameters, 2 hidden layers each having 200 nodes and 4 output parameters (27 × 200 × 200 × 4) with an initial learning rate 0.0001, using Adam optimizer and subjected to Z pre-processing method, to yield an accurate model with R2 = 0.907. The tuned DNN model, had a root mean square error of 21.06 MPa, 16.67 MPa, 2.36%, and 39.33 J, and root mean square percentage error of 4.7%, 2.9%, 7.7%, and 16.2%, for YS, UTS, EL and Akv respectively. Through comparative analysis, it was found that the accuracy of DNN model was higher than other classic machine learning algorithms. To interpret the model assumptions and findings, several local linear models were devised and analyzed to establish the link between process parameters and mechanical properties. Finally the tuned DNN model was deployed in the real-steel plant for online monitoring and control of steel mechanical properties, and to guide the production of targeted steel plates with tailored mechanical properties.

Histone H4-Specific Deacetylation at Active Coding Regions by Hda1C.

Histone acetylation and deacetylation play central roles in the regulation of chromatin structure and transcription by RNA polymerase II (RNA Pol II). Although Hda1 histone deacetylase complex (Hda1C) is known to selectively deacetylate histone H3 and H2B to repress transcription, previous studies have suggested its potential roles in histone H4 deacetylation. Recently, we have shown that Hda1C has two distinct functions in histone deacetylation and transcription. Histone H4-specific deacetylation at highly transcribed genes negatively regulates RNA Pol II elongation and H3 deacetylation at inactive genes fine-tunes the kinetics of gene induction upon environmental changes. Here, we review the recent understandings of transcriptional regulation via histone deacetylation by Hda1C. In addition, we discuss the potential mechanisms for histone substrate switching by Hda1C, depending on transcriptional frequency and activity.

Microstructure and mechanical properties of Al-Mg-Li-Sc-Zr alloy processed by spray deposition and thermo-mechanical processes

Al-Mg-Li-Sc-Zr alloy was prepared by spray deposition followed by extrusion and heat treatment processes. The effects of aging temperature on microstructure, phase transformation, and mechanical properties of the alloy were studied. The results show that the extruded alloy presents a typical fibrous structure with large amounts of secondary phases distributed along the extrusion direction. After solution and aging treatments, recrystallized structures are founded in the alloy, and the proportion of large size grains increases with the aging temperature increasing. TEM observation shows that the δ′(Al3Li) phase particles are homogeneously distributed in the Al matrix, leading to a significant enhancement of tensile strength. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the alloy after aging at 120 °C for 20 h reach 492.3 ± 9 MPa, 568.2 ± 6 MPa, and 5.8% ± 0.25, respectively. When the aging temperature rises from 120 to 160 °C，the dispersed δ′phases are coarsened gradually and the continuous striped S1(Al2MgLi) phases are observed at the grain boundaries, which causes the declination of strength and elongation of the alloy.

Predicting Tensile Properties of AZ31 Magnesium Alloys by Machine Learning

AZ31 magnesium alloys from different suppliers usually have different chemistry and processing histories, causing variance in their mechanical properties. In this work, we establish the quantitative relationship between alloy compositions, processing parameters, and mechanical properties by machine learning. Based on the artificial neural network (ANN) and support vector machine (SVM) algorithms, two models were built using a dataset with 112 data. Both models achieved good accuracy in predicting yield strength (YS), ultimate tensile strength (UTS), and tensile elongation (EL). To test their generalization ability, a new AZ31 extruded alloy was fabricated, with its chemical composition and processing history being documented. The YS, UTS, and EL of this material were measured and compared with model predictions. Relative errors for YS, UTS, and EL were 5.4%, 23%, and 272% by the ANN model, and 28%, 25%, and 143% by the SVM model, respectively. The reasons for the overestimation of the mechanical properties are discussed.

Macrostructure, microstructure and mechanical properties evolution during 8Cr4Mo4V steel roller bearing inner ring forging process

Hot ring rolling (HRR) is an advanced partial progressive forming technology that can directly manufacture various sizes of precision bearing rings. How to prefabricate the ring blank will affect the utilization rate of materials, flow lines distribution and microstructure in the forging of bearing rings. To improve product quality, a better understanding the evolution process of flow lines and microstructure during the forging process of bearing rings is needed. The purpose of this paper was to prefabricate the ring blank by back extrusion (BE) and use the HRR process (BE-HRR) to manufacture the pre-forged ring blank into 8Cr4Mo4V steel roller bearing inner ring. The development of flow lines, microstructure and mechanical properties during BE-HRR and spheroidizing annealing (SA) were systematically explored. By interrupting the separate BE-HRR processes were achieved resulting in analysis flow lines and characterization microstructure of each process. The macrostructure results show that the flow lines simulation results of each process are consistent with the experimental results. The reasonable flow lines distribution of roller bearing rings can be obtained by using this technology. The maximum deformation position of the BE and HRR process is in the inner diameter of ring. By combining optical microscopy (OM) and scanning electron microscopy (SEM) results were shown that the microstructure of the bearing ring is inhomogeneous in the whole BE-HRR process, but the microstructure of the bearing ring becomes uniform after SA. The primary carbides are distributed fibrously throughout the BE-HRR process and will not dissolve and disappear. The ultimate tensile strength (UTS) of HRR along the axial direction (AD) and circumferential direction (CD) is higher than that along the radial direction (RD), indicating distinct mechanical anisotropy due to different crack length and fracture paths along elongated grains. After SA, the elongation (EL) along the AD is significant higher than RD and CD owing to smaller grain sizes and microcracks tending to form and propagate first along the flow lines.

Influence of pinhão starch and natural extracts on the performance of thermoplastic cassava starch/PBAT extruded blown films as a technological approach for bio-based packaging material.

Films were produced using the blown extrusion method from blends made with cassava and pinhão thermoplastic starch, compostable polyester (poly(butylene adipate co-terephthalate, PBAT) and natural extracts (rosemary and green tea). The effect of the incorporation of the extracts and the type of starch added in the film properties were investigated following the mixture design (23 ) approach. Regression models and response surface curves were generated to predict the film properties. The effect of the cold storage (6°C and 17% of humidity relative, for 60 days) on the film properties was also investigated in order to simulate future applications. All the properties were mainly influenced by the extract type. The incorporation of the extracts decreased the lightness parameter and the films produced with green tea extract were more opaque than those made with rosemary. Starch/rosemary blends were more flexible, while the extract type did not have a significant effect on tensile strength (TS). Film elongation (ELO) ranged from 520% to 719% and might be comparable to some synthetic polymers. The water vapor permeability was improved in approximately 14% with addition of the extracts. The storage conditions, on the one hand, increased the TS, elastic modulus, and opacity of films and, on the other hand, decreased the elongation parameter. The thermal stability of films was not modified by adding extracts or varying the starch type. The results demonstrated that pinhão/cassava/PBAT blends and the natural extracts are a good alternative matrix to produce packagings with adequate mechanical and barrier properties. PRACTICAL APPLICATION: Extruded films produced from cassava or pinhão starch, poly(butylene adipate co-terephthalate) (PBAT) and natural extracts show technological potential to be used as active packaging for food products. Pinhão starch is a great alternative substitute to cassava starch and the incorporation of the commercial compostable polymer (PBAT) is necessary in order to confer suitable mechanical properties to extrusion process. The extrusion blown method, a process widely used by plastic industries, allows the scale-up of bio-based packagings for industrial scale.

Microstructures and Mechanical Properties of Al-2Fe-xCo Ternary Alloys with High Thermal Conductivity.

The microstructures, mechanical properties, and thermal conductivity (TC) of Al-2Fe-xCo (x = 0~0.8) alloys in as-cast, homogeneous annealed, and cool rolled states are systematically studied. Results indicate that appropriate Co modification (x ≤ 0.5) simultaneously improves the thermal and mechanical properties of as-cast Al-2Fe alloys. The improvement of TC is attributed to ameliorating the morphology of primary Al3Fe phases from needles to short rods and fine particles, which decreases the scattering probability of free electrons during the electronic transmission. However, further increasing the Co content (x = 0.8) decreases the TC due to the formation of a coarse plate-like Al2FeCo phase. Besides, the thermal conductivity of annealed Al-2Fe-xCo alloys is higher than that of as-cast alloys because of the elimination of lattice defects and spheroidization of Al3Fe phases. After cool rolling with 80 % deformation, thermal conductivity of alloys slightly increases due to the breaking down of Al2FeCo phases. The rolled Al-2Fe-0.3Co alloy exhibits the highest thermal conductivity, which is about 225 W/(m·K), approximately 11 % higher than the as-cast Al-2Fe sample. The ultimate tensile strength (UTS) and elongation (EL) of as-cast Al-2Fe-0.5Co (UTS: 138 MPa; EL: 22.0 %) are increased by 35 % and 69 %, respectively, compared with those of unmodified alloy (UTS: 102 MPa; EL: 13.0 %).

Non-destructive corrosion study on a magnesium alloy with mechanical properties tailored for biodegradable cardiovascular stent applications

An Mg-2Zn-0.6Zr-0.6Nd alloy for biodegradable cardiovascular stent applications was prepared through indirect extrusion. The alloy exhibited a superior combination of tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation (EL) of about 269 MPa, 298 MPa and 25.6 %, respectively. In addition, the non-destructive electrochemical frequency modulation (EFM) technique was used for the first time to investigate the corrosion behavior of Mg alloys combined with electrochemical impedance spectroscopy (EIS) in Dulbecco’s Modified Eagle’s Medium (DMEM) and in Hank’s solution. Compared with the corrosion rate of 0.07 mm/year in Hank’s solution, lower corrosion rate of 0.03 mm/year was achieved in DMEM. The significant differences between the corrosion rate trends were discussed and related with the composition of the corrosion layer formed. Depending on the biomimetic fluids tested, different corrosion products were precipitated on the alloy’s surface: a compact and homogeneous layer of MgxCay(PO4)z and Zn(OH)2 and organic compounds was formed in DMEM, whereas a partial coverage of MgxCay(PO4)z and Mg(OH)2 was formed in Hank’s solution.

Enhanced mechanical properties of Mg-Zn-Y-Zr alloy by low-speed indirect extrusion

Effects of extrusion temperature on microstructure and mechanical properties of low Zn and rare earth (RE) containing Mg-2.5Zn-0.7Y-0.4Zr alloy were investigated. It was subjected to indirect extrusion at 300°C and 350°C at low extrusion speed (0.3mm/s). The microstructures of as-extruded alloys exhibited both a bimodal grain structure consisting of refined dynamic recrystallized (DRXed) grains and elongated strips of non-recrystallized (un-DRXed) grains. Additionally, the fragmented Mg3Zn2Y3 (W) phase particles distributed along the extrusion direction and promoted dynamic recrystallization. Meanwhile, the amount of nanoscale MgZn2 and W phases were dynamically precipitated in Mg matrix during the extrusion process. The average size and volume fraction of DRXed grains decreased with the extrusion temperature decreasing from 350°C to 300°C, while the volume fraction of precipitates increased. The alloy extruded at 300°C exhibited superior mechanical properties with the ultimate tensile strength (UTS) of 347.1MPa, yield strength (YS) of 329.3MPa and elongation (EL) of 12.8%. The enhancement of yield strength was mainly attributed to fine DRXed grains and dense nanoscale precipitates. The strengthening mechanism and microstructure evolution were also discussed.

Role of Cu on the mechanical properties and microstructures evolution of Al-xCu-1Li-0.4Mg–1Zn-0.1Zr alloys

In this paper, mechanical properties and microstructures of the cast and extruded Al-xCu-1Li-0.4Mg–1Zn-0.1Zr alloys (x = 2.0, 3.0, 4.0, 4.5, 5.5, 6.5 wt%) were investigated. The results showed that the as-cast micrographs of alloys with different Cu content primarily consist of dendritic α-Al grains, and the intermetallic phases at the grain boundaries were Cu and Zr rich phases. After solution treatment, no recrystallization took place in extruded alloys, and the alloys mainly represented mixed textures composed of <111> and <100> fibers. Cu significantly affected the precipitation behavior of the extruded alloys. Only T1 (Al2CuLi) phases were observed in T6 (aging at 175 °C for 32 h) and T8 (3% pre-strain followed by aging at 150 °C for 32 h) treated alloy with 2 wt% Cu. Further increasing Cu contents (4.5 and 6.5 wt%) enabled the co-precipitation of T1 and θ' (Al2Cu) phases, as well as increased their density. In addition, the microstructures of grain boundaries of alloys with different Cu content showed dramatic differences. T1 phases precipitated at the grain boundaries of alloy containing 2 wt% Cu, while rare precipitation of T1 phases was observed at the grain boundaries of alloy with 6.5 wt% Cu. The yield strength (YS) of the alloys increased with the Cu content and the elongation (EL) showed an opposite trend. A good combination of ultra-high strength (YS = 684 MPa, ultimate tensile strength = 726 MPa) and ductility (EL = 6.3%) was obtained in T8 treated alloy containing 4.5 wt% Cu. The presence of the undesired coarse T2 (Al6CuLi3) phases at the grain boundaries resulted in the premature failure of the high Cu content alloys.

Machine learning for high-throughput field phenotyping and image processing provides insight into the association of above and below-ground traits in cassava (Manihot esculenta Crantz)

BackgroundRapid non-destructive measurements to predict cassava root yield over the full growing season through large numbers of germplasm and multiple environments is a huge challenge in Cassava breeding programs. As opposed to waiting until the harvest season, multispectral imagery using unmanned aerial vehicles (UAV) are capable of measuring the canopy metrics and vegetation indices (VIs) traits at different time points of the growth cycle. This resourceful time series aerial image processing with appropriate analytical framework is very important for the automatic extraction of phenotypic features from the image data. Many studies have demonstrated the usefulness of advanced remote sensing technologies coupled with machine learning (ML) approaches for accurate prediction of valuable crop traits. Until now, Cassava has received little to no attention in aerial image-based phenotyping and ML model testing.ResultsTo accelerate image processing, an automated image-analysis framework called CIAT Pheno-i was developed to extract plot level vegetation indices/canopy metrics. Multiple linear regression models were constructed at different key growth stages of cassava, using ground-truth data and vegetation indices obtained from a multispectral sensor. Henceforth, the spectral indices/features were combined to develop models and predict cassava root yield using different Machine learning techniques. Our results showed that (1) Developed CIAT pheno-i image analysis framework was found to be easier and more rapid than manual methods. (2) The correlation analysis of four phenological stages of cassava revealed that elongation (EL) and late bulking (LBK) were the most useful stages to estimate above-ground biomass (AGB), below-ground biomass (BGB) and canopy height (CH). (3) The multi-temporal analysis revealed that cumulative image feature information of EL + early bulky (EBK) stages showed a higher significant correlation (r = 0.77) for Green Normalized Difference Vegetation indices (GNDVI) with BGB than individual time points. Canopy height measured on the ground correlated well with UAV (CHuav)-based measurements (r = 0.92) at late bulking (LBK) stage. Among different image features, normalized difference red edge index (NDRE) data were found to be consistently highly correlated (r = 0.65 to 0.84) with AGB at LBK stage. (4) Among the four ML algorithms used in this study, k-Nearest Neighbours (kNN), Random Forest (RF) and Support Vector Machine (SVM) showed the best performance for root yield prediction with the highest accuracy of R2 = 0.67, 0.66 and 0.64, respectively.ConclusionUAV platforms, time series image acquisition, automated image analytical framework (CIAT Pheno-i), and key vegetation indices (VIs) to estimate phenotyping traits and root yield described in this work have great potential for use as a selection tool in the modern cassava breeding programs around the world to accelerate germplasm and varietal selection. The image analysis software (CIAT Pheno-i) developed from this study can be widely applicable to any other crop to extract phenotypic information rapidly.

Effects of aging treatment on the precipitation behaviors and mechanical properties of Al-5.0Mg-3.0Zn-1.0Cu cast alloys

Abstract This study investigates the relationship between aging temperature on the precipitation behavior and mechanical properties of a gravity cast Al-5.0Mg-3.0Zn-1.0Cu (wt%) alloy. After solution treatment at 470 °C for 24 h, alloys were aged at 120, 150 and 175 °C. Upon analyzing the samples, the alloys displayed different age hardening behaviors due to the variations in aging temperature. An increase in aging temperature not only reduced the peak aging time significantly, but also changed the distribution of precipitates. Numerous GPII zones and T′ precipitates (precursors of T-Mg32(AlZn)49) were homogeneously distributed within matrix at a higher aging temperature and the volume fraction of T′ precipitates increased. Tensile test results for peak-aged samples determined that both yield strength (YS) and ultimate tensile strength (UTS) increased, while elongation (EL) decreased with increasing temperature. The increase in the YS can be attributed to the higher volume fraction of T′ precipitates caused by the higher aging temperature. Moreover, the impact toughness decreased (due to a continuous decrease in EL) as the aging temperature increased. By adjusting aging temperature from 120 to 175 °C, YS increased from 377 to 451 MPa, while EL decreased from 13.8% to 5.2%. After peak aging treatment at 150 °C, the alloy appears to possess optimal mechanical properties with YS, UTS, EL and toughness being 441 MPa, 496 MPa, 9.6%, and 8.1 J/cm2, respectively. These finding suggest that there are many potential advantageous applications for this alloy within automobile components requiring high strength and toughness.

Influence of Ni and Bi microalloying on microstructure and mechanical properties of as-cast low RE LPSO-containing Mg–Zn–Y–Mn alloy

In this work, the high performance as-cast low RE (rare earths) Mg96.5Zn1Y1.5Mn1 alloys with LPSO (long-periodic stacking ordered) phase were fabricated by Ni and Bi microalloying, and the influences of Ni and Bi additions on microstructural evolution and mechanical properties in as-cast Mg96.5Zn1Y1.5Mn1 alloy were investigated. Results show that the Ni and Bi co-alloying can greatly refine the microstructure and facilitate the precipitation of 18R-LPSO phase. Meanwhile, in the Mg95.9Zn1Y1.5Mn1Ni0.5Bi0.1 alloy, the nucleation and growth ability of 18R-LPSO phase were higher than those of W phase, and the growth pattern of 18R-LPSO and W phase was optimized from coupled to divorced growth. Besides, the Mg95.9Zn1Y1.5Mn1Ni0.5Bi0.1 alloy exhibited superior mechanical properties with yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of 167±1 MPa, 239±1.6 MPa and 12±0.45%. Grain refinement, continuous 18R-LPSO phase with optimized growth pattern and the LPSO fibers precipitated in W phase were responsible for the outstanding mechanical properties.

Microstructure and mechanical properties of ultra-lightweight Mg-Li-Al/Al-Li composite produced by accumulative roll bonding at ambient temperature

Microstructural evolution and mechanical properties of ultra-lightweight Mg-14 wt% Li-1wt.% Al/Al-2wt.% Li composite produced by accumulative roll bonding (ARB) at ambient temperature were investigated. The computational simulation revealed the complicated stress and strain distribution in Mg-Li-Al and Al-Li layers during ARB process. The compositions of Al and Mg elements across the interface between Mg-Li-Al and Al-Li layers were increasingly homogeneous with the increase of ARB cycles due to the atomic inter-diffusion, indicating that the bonding between Mg-Li-Al and Al-Li layers was gradually improved. The grain sizes of Mg-Li-Al and Al-Li layers were decreased to about 300 nm and 200 nm after 4 cycles of ARB process, respectively. The brittle intermetallic compounds of Al3Mg2 and Al12Mg17 were gradually formed with the increase of ARB cycles. The microhardness and strength of Mg-Li-Al/Al-Li composite continuously increased, however, the ductility first decreased and then increased with the increase of ARB cycles. The tensile properties, with the ultimate tensile strength (UTS) of 308 MPa and the elongation (EL) of 17.4%, were achieved after 4-cycle ARB process.

Investigation on Microstructures and Mechanical Properties of the Hypoeutectic Al-10Si-0.8Fe-XEr Alloy

In this paper, the effect of Er addition (0.2, 0.5, 0.65, 0.8, 1.0, and 1.5 wt. %) on the microstructure evolution and tensile properties of as-cast hypereutectic Al-10Si-0.8Fe alloy was investigated. The phases and their morphologies in these alloys were identified by XRD and SEM equipped with EDX with the help of metallographic analysis techniques; the length of the secondary phase (LSP) and secondary dendrite arm spacing (SDAS) of α-Al grain were quantified. The results indicated that the second phases (primary Si, eutectic Si, and iron-rich phases) and α-Al grain were significantly refined when the addition of Er increased from 0 to 0.8 wt. %. The mean LSP and SADS values were decreased to a minimum value when the Er addition reached 0.8 wt. %. However, the second phases and α-Al grain became coarser when the level of Er increased more than 0.8 wt. %. The analysis of XRD shows that Er mainly exists in the form of Er2Si compound. The microstructure modification also has a significant effect on the mechanical properties of the alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) increase from 52.86 MPa, 163.84 MPa, and 3.45% to 71.01 MPa, 163.84 MPa, and 5.65%, respectively. From the fracture surface, the promotions of mechanical properties are due to the dispersion and pinning reinforcement caused by the Er2Si phase.

Microstructural and mechanical characteristics of 308L stainless steel manufactured by gas metal arc welding-based additive manufacturing

In this paper, gas metal arc welding-based additive manufacturing (GMAW-AM) was used to build thin-walled 308L stainless steel parts. The microstructural and mechanical characteristics of the built thin walls were investigated. The results show that the GMAW-AM thin-walled 308L is dominantly composed of columnar dendrites, which grow along the build direction when increasing the number of depositing layers. The microstructure of the GMAW-AM thin-walled 308L mainly consists of two phases: a small amount of δ ferrite phases displayed within γ austenite dendrites. The microhardness of built materials ranges from 155 ± 1.20 HV0.1 to 169 ± 5.67 HV0.1. The average ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of the GMAW-AM thin-walled 308L in the vertical direction are 531.78 ± 4.52 MPa, 343.67 ± 7.53 MPa, and 39.58 ± 1.38%, respectively, which are obviously lower than those in the horizontal direction (UTS: 552.95 ± 4.96 MPa, YS: 352.69 ± 8.12 MPa, and EL: 54.13 ± 1.29%).