Al-4 Wt Research Articles

Benchmark Al-Cu Solidification Experiments in Microgravity and on Earth

Predicting macrosegregation and grain structure, including the columnar to equiaxed transition (CET), in alloy solidification is an ongoing challenge. Gravity-driven melt convection and transport of unattached solid grains complicate such efforts. Cylindrical samples of aluminum alloys containing 4, 10, and 18 wt pct copper are solidified from the bottom upwards on Earth and in microgravity conditions aboard the International Space Station. The chosen alloys possess primary solid densities that are greater than, equal to, and less than their melt densities promoting different gravity-driven solid transport phenomena. Significant differences in grain structure are observed between microgravity and terrestrial samples. All microgravity samples are entirely equiaxed, while the terrestrial samples exhibit a CET. The columnar grains near the cooled surface in the terrestrial samples can only be attributed to melt convection. The Al-4 wt pct Cu terrestrial sample shows evidence of grain sedimentation, while the Al-18 wt pct Cu terrestrial sample exhibits the effects of grain floatation. Measurements of eutectic fraction and solute concentration in the samples show inverse segregation due to shrinkage-driven flow in all samples. Terrestrially solidified samples have areas of high solute concentration that are not uniformly distributed over the diameter, indicating the presence of melt convection. The eutectic and macrosegregation measurements generally have good correspondence. Temperature, grain structure, eutectic fraction, and macrosegregation data are presented as benchmark data to validate future modeling efforts. Heat flux boundary conditions on the sample are determined using thermal modeling. Thermal process parameters are calculated for all samples.

Microstructure-Based Modeling and Mechanical Characteristics of Accumulative Roll Bonded Al Nanocomposites with SiC Nanoparticles

This research work aims to fabricate the Al-4 wt.% SiC nanocomposite using the accumulative roll bonding (ARB) technique. Moreover, a finite element model based on real microstructure representative volume element representation and cohesive zone modeling was developed to predict the mechanical response of the produced composites. The results demonstrated that SiC particles were homogenously distributed inside the Al matrix after five passes. The tensile strength and hardness were improved by increasing the number of ARB passes. The microhardness of an Al-4%SiC composite subjected to five ARB passes was increased to 67 HV compared to 53 HV for Al sheets subjected to the same rolling process. Moreover, owing to greater bonding and grain refinement, tensile strength was increased by a factor of three compared to pure Al. The result of the proposed micro-model successfully predicts the experimentally obtained results of the Al–SiC macro composite. The numerically obtained stress–strain curve was comparable with the experimental one. The results also showed that the size of the used RVE was significantly influential in the prediction of the stress–strain behavior.

Dendrite morphology in Al-20 wt%Cu hypoeutectic alloys in 24 T high magnetic field quantified by ex-situ X-ray tomography

The morphology of the primary α-Al crystal in a solidifying Al-20 wt%Cu alloy under the high static magnetic field (HMSF) was studied by using the ex-situ X-ray computed tomography technique. The side arms were the seaweed and the dendrite under 0 T and 24 T HSMF, respectively. They were identified by 2D slices and 3D reconstruction of dendrites. The secondary dendrite arm spacing increased and the interface curvatures decreased under the HSMF. The growth angle between the secondary dendrite arms and their stems was close to 90° in the case of the 24 T HSMF. These were attributed to the decrease of constitutional supercooling caused by magnetohydrodynamic effect.

Al–Ni alloy-based core-shell type microencapsulated phase change material for high temperature thermal energy utilization

Latent heat thermal energy storage (LHTES) using alloy-based phase-change materials (PCMs) is a promising technique for stabilizing the power supply of grid-connected renewable energies. In particular, recently developed alloy-based microencapsulated PCMs (MEPCMs) are attracting considerable attention owing to their ease of handling and ability to overcome the problems of corrosion and melting leakage experienced by alloy PCMs. To expand high-temperature LHTES, more MEPCMs need to be developed. In this study, an MEPCM was developed using Al-5 wt.%Ni alloy (melting point 640°C). Microencapsulation was performed in two steps: 1) Al hydroxide layer formation on the surface of PCM particles by boehmite treatment in boiling water for 1 h or 3 h and 2) Al 2 O 3 shell formation by heat oxidation treatment in an O 2 atmosphere. The prepared MEPCM consisted of an α-Al 2 O 3 shell and an Al–Ni alloy core. The sample after 1 h of boehmite treatment and heat oxidation treatment had melting and solidification latent heat capacities of 241 J g –1 and 251 J g –1 , respectively. The developed MEPCM maintained its original shape and high latent heat capacity, even after 100 cycles of melting and solidification. The developed Al–Ni alloy-based MEPCM is expected to be applied to next-generation LHTES, in which a large-scale and ultrafast heat exchange system is employed in a small space by cascade configuration with other MEPCMs with different melting points. In addition, the formation of the Al–Ni alloy core/α-Al 2 O 3 shell structure was investigated thermodynamically, providing insights that will promote the development of Al- X alloy-based MEPCMs in the future. • Al–Ni alloy based microencapsulated phase change materials (MEPCMs) were developed. • The prepared MEPCM consisted of an α-Al 2 O 3 shell and an Al–Ni alloy core. • The MEPCM exhibited high thermal storage capacity about 241 - 251 J g -1 . • The MEPCM had melting temperature of 640°C. • They are good candidates for high-temperature thermal energy storage application.

Non-regular dendritic pattern selection induced by interface energy anisotropy in the directional solidification of Al-3 wt% Mg single crystals

• Finding plate-like and hyperbranched seaweed in 3D conditions of metallic alloy. • Constructing a non-regular dendritic pattern selection map. • Well understanding effect of interface energy anisotropy on the dendritic pattern. Dendritic morphology and pattern selection are fundamentally important issues in solidification cycles. Here, a well-designed experiment was employed to investigate the solid–liquid interface energy anisotropy on the directionally solidified microstructures of Al-3 wt% Mg single crystals. Various dendritic morphologies, including regular dendrite, plate-like seaweed and hyperbranched seaweed, were found along the <100>, <110> and <111> orientations, respectively. The primary dendritic arm spacing (PDAS) of the seaweed pattern is closely related to the interface energy anisotropy and deviates from the current PDAS model. A non-regular dendritic pattern selection map is constructed to interpret the different dendrites occurring in alloy solidification.

Influence of Al11Ce3 Size and Distribution on the Electrochemical Properties of Sonoprocessed Al-10 wt.% Ce Alloy

Solidification of Al–Ce alloys under ultrasonic vibrations (Sonoprocessing) has a significant effect on the refining of Al11Ce3 intermetallic, which plays a key role in controlling the properties of this group of high-performance characteristics. In the current research, a group of as-received Al-10 wt% Ce alloys that were sonoprocessed under different temperatures was characterized. The influence of Al11Ce3 intermetallic size and distribution on the electrochemical properties of these alloys was investigated. Polarization tests in 3.5% NaCl solution were carried out and the recorded Tafel and impedance curves were studied. The corrosion test results were related to the microstructure characteristics as affected by sonoprocessing. Investigation of the as-received samples showed that ultrasonic vibrations broke the long lath-shaped particles of Al11Ce3 and obviously decreased their size and increased their surface area fraction. Sonoprocessing at the optimum temperature, 655 °C, reduced the Al11Ce3 particles size by 90% and enhanced their distribution in the matrix. This in its turn resulted in significant effects on their electrochemical behavior. Polarization tests showed that the corrosion rate of the un-sonoprocessed specimen decreased from ~ 0.00068 to 0.00006 mm/year after processing at the optimum condition (655 °C), and the polarization resistance increased from ~ 71 to 343 kΩ. By increasing the temperature of ultrasonic treatment beyond 655 °C, and the corresponding coarsening of the intermetallic particles, the corrosion rate slowly increased again, and concurrently, the polarization resistance decreased. The size and distribution of the intermetallic particles also influenced the formation of the corrosion pits, where the optimum sample showed shallow pits compared to those observed in the unprocessed specimen. This emphasizes the role of sonoprocessing in controlling the microstructure features and hence the electrochemical properties of Al-10 wt% Ce alloys.

Few-layered graphene reinforced Al-10 wt% Si-2 wt% Cu matrix composites

Few-layered graphene (FLG) reinforced Al-10 wt% Si-2 wt% Cu (Al10Si2Cu) matrix composites were fabricated via a powder metallurgical route. FLG powders were produced in an originally designed DC arc reactor via arc discharge method. Al, Si, Cu and FLG powders were subjected to high-energy ball milling at different durations to produce ternary Al alloy with homogeneously dispersed FLG, and bulk composites were fabricated via subsequent uni-axial compaction and pressureless sintering. The effects of varying FLG amounts and milling duration on the properties of the powder and bulk samples were investigated. The characterization of as-blended and mechanically alloyed (MAed) powders and their sintered forms were performed in terms of microstructural, thermal, mechanical, wear and corrosion properties. According to the results, the hardness values of the 4 h MAed Al10Si2Cu-xFLG composites were determined as 102, 154, 191 and 241 HV for x = 0, 1, 2 and 5 wt%, respectively. Despite the greater hardness value of the Al10Si2Cu-5FLG-4h composite, its compressive strength was low due to its brittle structure. The highest compressive strength was shown by the Al10Si2Cu-1FLG as 463 MPa by an approximate increase of 53% compared to that of the Al10Si2Cu matrix. Moreover, the tribology tests showed that FLG addition (up to 2 wt%) improved the wear rate of the Al10Si2Cu matrix. However, a deteriorative effect of FLG on the corrosion resistance of the composites was determined.

The Effect of Tin on Microstructure and Properties of the Al-10 wt.% Si Alloy.

In this paper, the results from studies regarding near-eutectic Al-Si alloys with Sn as an alloying addition are presented. In most Al-Si alloys, tin is regarded as a contaminant; thus, its amount is limited to up to 0.3 wt.%. The few studies that can be found in the literature regarding the behaviour of tin in aluminium alloys suggest the beneficial effect of this element on selected properties. However, these results were obtained for hypereutectic Al-Si alloys or wrought aluminium alloys. In our studies, the influence of tin contents of up to 1.7 wt.% was determined on the AlSi10 alloy. Thermal analysis, measurements of the mechanical properties of the cast and heat-treated alloy, metallographic observations (light microscopy, scanning electron microscopy), and EDS (X-ray energy dispersive spectrometry) measurement allowed us to fully describe the effect of tin on the aluminium alloy. The results of the thermal analysis showed changes in the range of the α-Al solution crystallisation and the α+β eutectic through a decrease in the alloy’s solidification start point and eutectic solidification point. As a result, the elongation of the alloy was more than double in the AlSi10Sn1.7 alloy, with an A5 value of 8.1% and a tensile strength that was above 200 MPa.

In situ radiographic study of the grain refining behavior of Al3Sc during the solidification of Al-10Cu alloy

Grain refinement of Al alloys inoculated by rare earth elements, such as Sc, has been extensively acknowledged, while the practical behavior of how inoculant Al3Sc particles affect the refinement in solidification has not been clarified due to the non-transparency of the solidification process. Here, the microstructural evolution of primary Al3Sc particles and α-Al grains in Al-10 wt.% Cu alloy solidifications with 0.2 wt.%, 0.6 wt.%, and 1.0 wt.% Sc additions was investigated by in situ synchrotron X-ray radiography. The detailed mechanisms of curve motion of grains (CMG) and melt convection were revealed. The efficient grains nucleation, uniformly scattered small initial grains, and long duration of melt convection contributed to the best refinement in the 0.6 wt.% Sc addition sample. This work provides a deep insight into grain refinement in solidification with Sc addition, which will enlighten the composition design and casting process of Al alloys inoculated by rare earth elements.

Microstructure evolution and mechanical properties evolution of high-Zn Al-Zn alloys prepared by cross accumulative roll bonding combined with heat treatment process

The cross accumulative roll bonding (CARB) combined with the heat treatment process was used to develop high-Zn Al-xZn alloys with 20 and 50 wt% Zn. The effect of the Zn content and fabrication process on the microstructural evolution, microhardness, tensile, and wear behaviors was investigated by using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDS), microhardness indentation, uniaxial tensile, and wear testing (pin-on-disk) at room temperature. The microstructure of the Al-20 wt% Zn alloy featured α-Al granular structures, whereas by Zn content increasing to 50 wt% the structure was α + η eutectoid structures with a fine distribution. The increase of the Zn element from 20 to 50 wt% was accompanied by a significant increase in tensile strength and also microhardness, but reduction in the elongation percentage of the Al–xZn alloys. Additionally, the wear resistance was improved as the Zn content was increased from 20 to 50 wt%. Finally, mechanical results confirmed that by increasing Zn content in the developed alloys the mechanical properties improved.

Microstructure Analysis of Al-7 wt% Si Alloy Solidified on Earth Compared to Similar Experiments in Microgravity

During ground-based solidification, buoyancy flow can develop by the density difference in the hypoeutectic type of the alloys, such as Al-7 wt% Si alloy. Buoyancy flow can affect the thermal field, solute distribution in the melt, and the position and amount of the new grains. As solidification is a very complex process, it is not very easy to separate the different effects. Under microgravity conditions, natural convection does not exist or is strongly damped due to the absence of the buoyancy force. Therefore, experiments in microgravity conditions provide unique benchmark data for pure diffusive solidification conditions. Compared to the results of the ground-based and microgravity experiments, it is possible to get information on the effect of gravity (buoyancy force). In the framework of the CETSOL project, four microgravity solidification experiments were performed on grain refined (GF) and non-grain refined Al-7 wt% Si alloy onboard the International Space Station in the Materials Science Laboratory. These experiments aimed to study the effect of the solidification parameters (solid/liquid front velocity vSL, temperature gradient GSL) on the grain structure and dendritic microstructures. The microgravity environment eliminates the melt flow, which develops on Earth due to gravity. Four ground-based (GB) experiments were performed under Earth-like conditions with the same (similar) solidification parameters in a vertical Bridgman-type furnace having four heating zones. The detailed analysis of the grain structure, amount of eutectic, and secondary dendrite arm spacing (SDAS) for different process conditions is reported and compared with the results of the microgravity experiments. GB experiments showed that the microstructure was columnar in the samples that do not contain GF material or in case the solid/liquid (vSL front velocity was slow (0.02 mm/s)). In contrast, in the sample which contained GF material, progressive columnar/equiaxed transition (PCET) was observed at vSL = 0.077 mm/s and GSL = 3.9 K/mm. The secondary (SDAS) dendrite arm spacing follows the well-known power law, SDAS=K[t0]13, where K is a constant, and t0 is the local solidification time for both GB and µg experiments.

Investigation of Ti1−x(Zr,Ta,V,W)xB2 and Al3Ti1−x(Zr,V)x grain refiners in additively manufactured Al-2 wt%Cu alloys by a high throughput method

Grain refinement plays a central role in powder bed fusion (PBF) additive manufacturing by preventing hot cracking and thus enabling the development of high-strength alloys. However, the mechanism behind grain refinement is not fully understood for conventional casting, nor for PBF. In this work, a high throughput method have been used to produce Al-2 wt%Cu alloys with additions of Ti1-xM(Zr,Ta,V,W)xB2, Al3Ti1-xM(Zr,V)x or AlB2 grain refiners for 0.1 < x < 0.9. It was found that grain size varied with x, M and the sum of Ti + M. Ti1-xMxB2 grain refiners offered no advantage over Al3Ti1-xMx. Overall, Ti and Zr provide the best grain refinement, both as Ti1-xMxB2 and Al3Ti1-xMx. However, Ti1-xZrxB2 had a grain refinement minimum around x = 0.65–0.70. The behavior was similar with Ta, but to a lesser extent. V and W had detrimental effects on grain refinement. Despite the fact that no AlB2 particles were observed, additions of B provided excellent grain refinement and was more efficient than Ti below 0.5at%. Ti1-xMxB2 lattice parameters varied with x and followed Vegard’s law, however, a clear relationship between grain size and epitaxial strain/lattice match could not be established. Similarly, the growth restricting factor alone was not a predictor of grain size.

Microstructural evolution of Al–15Fe alloy produced by mechanical milling and centrifugal atomization

In this study, the Al-15 wt % Fe powders were prepared using two methods: (1) milling of the initial alloy in a ball or a planetary mill; (2) centrifugal atomization. The effect of milling time and distribution of temperature field during atomization on the morphology and microstructure of the Al-15 wt % Fe alloy powders were investigated. After milling, the powders have an agglomerate structure with a size of Al13Fe4 about 4.1–5.4 μm. Using centrifugal atomization at a blades rotation speed of 2800 rpm resulted in a microstructure consisting of α-Al-matrix, stable Al13Fe4 (10–15 μm) and random oriented short fibres of metastable Al6Fe (2.3 ± 2.2 μm). Randomly oriented fibres are formed due to deformation processes that act on the particles during cooling and crystallization. The formation of the metastable Al6Fe is associated with a high cooling rate of nearly 106–108 °C/min. The influence of the particle shape on the temperature field was simulated. The stable Al13Fe4 occurs in the centre of the powders according to the low solidification velocity. The crystallization of a uniform structure is possible for particles of regular shape. The matrix of the atomized powder has a cellular microstructure, which introduces an additional reinforcing effect to the Al-15 wt % Fe alloy.

Nanopowder derived Al/h-BN composites with high strength and ductility

Al/h-BN composites with high tensile and compressive strength at room and elevated temperatures, as well as enhanced ductility, were obtained by a combination of ball milling (BM) and spark plasma sintering (SPS) using Al and hexagonal BN nanopowders (0, 1, 2, 3, 4, 5, and 10 wt% of h-BN). The use of two types of nanopowders is intended to ensure uniform distribution of the reinforcing phase and improve Al-BN chemical interaction at the manufacturing stages by increasing the surface-to-volume ratio. Due to Al with h-BN interaction, the Al/h-BN composites were simultaneously strengthened by three types of nanoparticles: Al2O3, AlN(O) and h-BN, predominantly located along the Al grain boundaries. Compared to BM+SPS aluminum, the tensile strength of Al-2 wt%BN composite increased by 82% (25 °C), 64% (300 °C), and 65% (500 °C), and the compressive strength by 107–119% (25–500 °C) while maintaining high elongation to failure in tension (13.6%, 11.6% and 10.8%) and compression (12.6%, 13.1% and 8.1%) at 25 °C, 300 °C, and 500 °C, respectively. In terms of combination of tensile and compressive strength at room and elevated temperatures, the Al/h-BN materials are superior to many other Al-based composites. The high strength and relative elongation to fracture of the Al/h-BN composites can be explained by the formation of a heterogeneous microstructure consisting of pure Al grains surrounded by a metal-matrix composite material with fine metal grains and reinforcing ceramic nanoinclusions. The obtained results significantly expand the scope of Al/h-BN materials, since their strength at 500 °C is higher than that of pure Al at room temperature.

Improving mechanical properties of a cast Al–Mg alloy with high Mg content by rapid solidification

Cast Al–Mg alloys with high Mg contents (>10 wt%) have received particular attention due to much lower density than those of other cast Al alloys. However, high amounts of coarse dendritic Al–Mg intermetallic phases substantially deteriorate both strength and ductility. This work aims to reduce amount and size of Al–Mg intermetallic phases by rapid solidification (RS) and to improve both strength and ductility in a cast Al-15 wt%Mg alloy. This paper reports a study on Al-15 wt%Mg alloy processed by a RS technique, namely twin-roll casting (TRC). The results of optical microscopy, electron backscatter diffraction and scanning electron microscopy analysis show refined Al grains and refined granular Al3Mg2 particles, and the results of X-ray diffraction analysis reveal the increased Mg solid solubility and correspondingly the decreased amount of Al3Mg2 phase, in the TRC Al-15 wt% alloy, as compared to the conventionally mold cast (CMC) counterpart. Consequently, the tensile testing results show 0.2% offset yield strength of 243 MPa and ultimate tensile strength of 355 MPa, accompanied by uniform elongation of 3.6%, in the TRC Al-15 wt% alloy, relative to premature fracture in the CMC counterpart. The microstructural features and the mechanisms underlying improved strength and ductility in the TRC Al-15 wt%Mg are analyzed and discussed.

Effect of retained austenite on the microstructure and mechanical properties of cold-rolled medium-manganese Q&P steel

ABSTRACT The effect of retained austenite stability on microstructure evolution and mechanical properties of a new cold-rolled medium-manganese steel (0.12C, 7.69Mn, 1.45Si, 2.76Al wt-%) under intercritical annealing Q&P process at different partitioning temperatures was investigated. The evolution of retained austenite was characterized and statistically analysed using SEM, TEM, EBSD, and XRD techniques. The results show that the stability of retained austenite depends to a large extent on the applied heat treatment and is mainly attributed to the retained austenite content and morphology, whose carbon content is not the main influence. More retained austenite content and the formation of heterogeneous austenite structures (granular, massive, lamellar) are observed at a partitioning temperature of 150°C. The retained austenite of different morphologies has different stabilities and can sustain the TRIP effect at different strain stages, obtaining the best comprehensive mechanical properties with 34.5% elongation and the product of tensile strength and elongation is up to 43.5 GPa·%.

Challenges and Latest Developments in Diffusion Bonding of High-Magnesium Aluminium Alloy (Al-5056/Al-5A06) to Stainless Steels

The aim of this work was to investigate the challenges associated with bonding Al-Mg alloys and develop a new method for bonding these alloys to steels. During an extensive R&amp;D project, over 80 attempts, using 11 methods, were made to bond Al-6 wt.% Mg alloy (Al-5056/Al-5A06) to two types of stainless steels (heat-resistant 1Cr18Ni9Ti and conventional 316). Wide ranges of temperature (500 °C to 580 °C), pressure (0.5 MPa to 10 MPa) and time (1 min to 2 h) were used when direct diffusion bonding of these alloys. Then, effects of using various interlayers and brazing foils were investigated. The interlayers used in this work were gallium, pure titanium, copper and aluminium foils, aluminium 6061 alloy sheets, aluminium-silicon brazing foils, zinc and zinc alloy foils as well as an active brazing foil (known as Incusil-ABA containing silver, copper, indium and titanium). Several complex and multi-stage processes, using up to 3 different interlayers in the same joint, were also developed and assessed. Examination and assessment of the bonded samples, including failed attempts, paved the way of developing new methods for bonding these dissimilar materials. A number of samples with tensile strengths from 200 MPa to 226 MPa were made by using complex combinations of 2 or 3 interlayers and triple-stage bonding cycles. The highest recorded bond strength was 226 MPa in the as-bonded condition. This value is above the measured yield strength (134 MPa) and about 93% of the measured ultimate strength (243 MPa) of the parent Al-Mg alloy after it was subjected to the same bonding cycle. Since the use of complex processes was not feasible for bonding large components, a simpler and more practical bonding cycle was also developed in the project. Using the simpler process, joints with tensile strengths around 90 MPa could be made. This article also sheds light on the difficulties associated with brazing and soldering aluminium alloys with a high magnesium content.

Effect of Zn content on microstructure and properties of hypoeutectic and near-eutectic Al-Si alloys

In this research, the microstructure and mechanical properties of permanent mould cast Al-Si (7 wt.% and 12 wt.%) alloys without and with different amounts of Zn (1 wt.%, 2 wt.% and 4 wt.%) were analysed. The Al-xSi-yZn alloys have been prepared through a stir casting process using an Al-15 wt.% Si master alloy at 800 °C. Optical microscopic analyses have revealed variation in the α-Al matrix and Si needles in the alloy with the variation in Zn content. The mechanical properties analysis has shown that the hardness, tensile strength and wear resistance of the alloys increase with the addition of Si but decrease with the addition of Zn, within the limit of the alloying additions of the present research.

Study of grain boundary orientation gradients through combined experiments and strain gradient crystal plasticity modeling

A combined experimental and strain gradient crystal plasticity framework is presented for studying the development of orientation and misorientation gradients at the grain boundaries during plastic deformation. The regions in the vicinity of prior-deformation grain boundaries experience localized plastic deformation and are referred to as Near Boundary Gradient Zones (NBGZs). Deformed microstructures of an aluminum–magnesium (Al–6wt.% Mg) alloy are studied using Electron Back Scattered Diffraction (EBSD) during progressive tensile deformation. Orientation and misorientation gradients at the prior-deformation grain boundaries are quantified on grain pairs with different combinations of crystallographic orientations. Realistic virtual microstructures are then simulated using a strain gradient crystal plasticity finite element framework to study the evolution of local misorientations, stresses and strains and their correlation with the underlying substructure. The simulated microstructures indicate that the average profiles of the Geometrically Necessary Dislocation (GND) density correlates with the local misorientation, while the average profiles of the Statistically Stored Dislocation (SSD) density correlates with the effective plastic strain in these NBGZs. The combined experimental and modeling analysis reveals that the width (mean with deviation) of the distribution of the length of NBGZs, normalized by the grain size, scales with the initial grain-average Schmid factor. Further, our results also suggest a possibly strong correlation between the length of the NBGZ and the grain size.

Tailoring the tensile properties of AZ91 magnesium alloy via grain refinement

Grain refinement of AZ91 alloy was achieved via the addition of a modified Al-B inoculant to the melt, where a pronounced heterogeneous nucleation effect by AlB2 particles was observed via addition of Al-8 wt-% B master alloy up to 0.3 wt-%. Moreover, hot extrusion remarkably enhanced both strength and ductility via developing an equiaxed microstructure by dynamic recrystallisation (DRX), fragmentation/dissolution of eutectics (containing β-Mg17Al12 compound) during hot deformation, and amending casting defects. Both as-cast and extruded data followed the same Hall–Petch plot, implying that the grain size refinement is the main strengthening mechanism. Accordingly, grain refining via inoculation and thermomechanical processing was found to be a viable approach for the enhancement of strength-ductility trade-off through the improvement of tensile toughness.