Master Alloy Research Articles

Study on Refining Grain and Microalloying Effect of Al–5Er Master Alloy

Study on Refining Grain and Microalloying Effect of Al–5Er Master Alloy

Al-Ti-C (CNTs) master alloys improve room temperature and high-temperature mechanical properties of ZL205A alloy

The insufficient high-temperature properties of Al-Cu alloys represent a significant obstacle to their further development. The use of master alloy refiners can enhance the mechanical properties while refining the grains. This paper describes the preparation and characterization of Al-Ti-C (CNTs) master alloys containing submicron TiC particles through the aluminum melt reaction method, utilizing graphite powders (GPs) and (CNTs) as carbon sources,respectively.The effects of these two types of intermediate alloys on the microstructures and high-temperature mechanical properties of the ZL205A alloy were investigated at varying additive amounts. The results indicate that the Al-Ti-C (CNTs) master alloys contain TiC particles measuring up to 183 nm and 480 nm, respectively, with the Al-Ti-CNTs demonstrating a superior effect on the refinement of the ZL205A alloy. The optimal mechanical properties were achieved upon the addition of 0.3 wt% of the master alloy to the ZL205A alloy. The mechanical properties improved from 341.53 MPa (yield strength), 371.68 MPa (tensile strength), and 3.3 % elongation without the addition of master alloys to 413.20 MPa, 471.82 MPa, and 11.2 % with the addition of Al-Ti-CNTs and to 440.85 MPa, 492.61 MPa, and 10.8 % with the addition of Al-Ti-C, respectively.At a high temperature of 300°C, the mechanical properties of the ZL205A alloy improved from 144.0 MPa and 10.8 % (Al-Ti-C) to 174.87 MPa and 11.2 %, and 195.1 MPa and 13.8 % (Al-Ti-CNTs). The TiC particles generated in situ under a different carbon sources demonstrated distinct mechanisms in the grain refinement of the ZL205A alloy. TiC (GPa) with a larger size primarily impeded the further growth of grains, while TiC (CNTs) promoted the formation of crystalline nuclei and heterogeneous nucleation sites, thereby achieving grain refinement. Large-sized TiC particles prepared using graphite as the carbon source hindered further grain growth, whereas TiC produced using carbon nanotubes promoted the formation of nuclei and heterogeneous nucleation sites, resulting in grain refinement. In addition, both types of TiC particles contribute to the densification and strengthening of the ZL205A alloy through fine grain strengthening, precipitation strengthening, Orowan strengthening, load transfer strengthening, the pinning effect, and thermal mismatch strengthening. However,TiC(CNTs) exhibits a greater contribution to strength due to its high quantity and small size.

Mechanical energy absorption capacity of the porous Ti-6Al-4V alloy under quasi-static and dynamic compression

Porous materials are very efficient in absorbing mechanical energy in different applications. In the present study, porous materials based on the Ti-6(wt.%)Al-4V alloy were manufactured with the use of two different powder metallurgy methods: i) blended elemental powder approach using titanium hydride (TiH2) as well as V-Al master alloy powders and ii) using hydrogenated Ti-6-4 pre-alloyed powder. The powder compacts were sintered with additions of ammonium bicarbonate as a pore-holding removable agent. The emission of hydrogen from hydrogenated powders on vacuum sintering and the resulting shrinkage of powder particles permitted the control of the sintering process and creation of anticipated porous structures. Mechanical characteristics were evaluated under quasi-static and dynamic compressive loading conditions. Dynamic compression tests were performed using the direct impact Hopkinson pressure bar technique. All investigations aimed at characterizing the mechanical energy-absorbing ability of the obtained porous structures. The anticipated strength, plasticity, and energy-absorbing characteristics of porous Ti-6-4 material were evaluated, and the possibilities of their application were also discussed. Based on the obtained results, it was found that porous Ti-6-4 material produced with a blended elemental powder approach showed more promising energy absorption properties in comparison with pre-alloyed powder.

Effects of surface-active elements on wettability and interfacial reaction between DD5 superalloy and Al2O3-based ceramic shell

The study investigates the effects of oxygen-sulfur content, holding temperature, and time on the wettability and interfacial reactions between DD5 superalloy and Al2O3-based ceramic shells through non-in-situ sessile drop experiments. Lowering the oxygen-sulfur content in the DD5 master alloy, as well as reducing the holding temperature and time, leads to an increase in the wetting angle and a mitigation of interfacial reactions. Improved wettability promotes interfacial reactions, while intensified interfacial reactions further spread the alloy melt, enhancing its wettability. The main products of the interfacial reaction between the DD5 alloy and Al2O3-based ceramic shells are Al2O3 and Si, with the process being influenced by the presence of Al. When the oxygen-sulfur content is controlled within 6 ppmw, the wettability will undergo a characteristic transformation, resulting in a sharp increase in the wetting angle. It demonstrates that the ultra-pure DD5 master alloy plays a crucial role in reducing wettability and interfacial reaction, as well as slowing down the tendency of the hetero-crystal formation. Therefore, it is of great engineering significance to further reduce the content of oxygen-sulfur impurity elements in DD5 superalloy.

First-principles study of Ti adsorption on Al4C3 (0001) surface

Al4C3 phase is hypothesized to undergo a solid–solid phase transition into TiC, thereby facilitating the heterogeneous nucleation of α-Al. However, capturing this transition process experimentally is challenging, which undermines the credibility of this transition theory. In this study, first-principles calculations are employed to investigate the feasibility of Ti atom adsorption on the exposed (0001) surface of the Al4C3 crystal, providing theoretical support for the phase transition hypothesis. The findings indicate that Ti adatoms can effectively adsorb on the C-terminated (0001) surface, whereas adsorption on the Al-terminated surface is thermodynamically unfavorable. Upon structural optimization, Ti adatoms at bridge site B, top site T, and hollow site H1, irrespective of coverage, migrate towards the most stable hollow H2 site. Electronic structure analysis reveals that the bonding between the Ti adatom at the H2 site and the surface layer C atoms is primarily covalent, while the bonding with subsurface layer Al atoms is metallic. Additionally, Ti atom adsorption induces polarization of the bonding electron cloud between Al and C atoms. This study provides theoretical support for the Ti-induced transformation of the Al4C3 to TiC phase via surface adsorption, paving the way for the development of high-performance master alloys based on phase transition theory.

Achieving significant grain refinement efficiency in Mg-Al alloys via a GNP@MgO composite refiner

Master alloys containing Zirconium (Zr) serve as effective grain refiners in most commercial cast magnesium (Mg) alloys. However, their efficacy is diminished in Mg–Al series alloys due to the formation of Al–Zr compounds. In this work, a novel Mg-GNP@MgO master alloy was prepared utilizing the in-situ reaction between CO2 and Mg. The grain refinement efficiency of this composite inoculation on Mg–9Al alloys was systematically investigated using SEM-EBSD, HRTEM observations, Density Functional Theory (DFT), and Sharp Interface Model (SIM) calculations. The findings suggest that the composite grain refiner (GNP@MgO) exerted a notable refining influence on Mg–9Al alloy. Through the conventional casting process, the average grain size was refined to approximately 13 μm upon the addition of 3 vol% GNP@MgO, achieving a grain refinement efficiency of 90 %. The enhanced refining efficiency arises from the synergistic control over the nucleation and growth processes of α-Mg grains, facilitated by GNP@MgO particles. This process includes improved heterogeneous nucleation, triggered by the newly formed Al4C3 phases through the interaction between GNPs and Al element, followed by the limited expansion of α-Mg grains induced by the nano-sized MgO particles. The MgO particles predominantly gather around grain boundaries to establish stable nano-coating layers, thereby exerting a substantial Zener pinning effect. The pinning role played by the MgO nanoparticles was also verified by a sharp interface model. The findings in this work not only carve out a new avenue for the grain refinement of cast Mg–Al alloys but also inspire fresh perspectives for the development of novel grain refiners.

Dual Grain Refinement Effect for Pure Aluminum with the Addition of Micrometer-Sized TiB2 Particles.

The inefficiency of grain refinement processes has traditionally been attributed to the limited utilization of heterogeneous nucleation particles within master alloy systems, resulting in the formation of abundant inactive particles. This study aims to investigate the alternative influences of particles by incorporating external micrometer-sized TiB2 particles into the grain refinement process. Through a series of experiments, the refinement efficiency, grain refinement mechanism, and resultant microstructure of TiB2 particle-induced grain refinement specimens are comprehensively examined using various microscopy and analytical techniques, including polarization microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Our findings demonstrate a direct correlation between increased levels of TiB2 particles and enhanced grain refinement efficiency. Moreover, the microstructure analysis reveals the distribution of TiB2 particles along grain boundaries, forming a coating due to self-assembly phenomena, while regions with a lower particle content may exhibit irregular grain structures. DSC analysis further confirms reduced undercooling, indicating the occurrence of heterogeneous nucleation events. However, TEM observations suggest that heterogeneous nucleation is not significantly influenced by the growth restriction factor attributed to TiAl3 2DC compounds. The grain refinement mechanism involving TiB2 particles is elucidated to entail both heterogeneous nucleation and physical growth restriction effects. Specifically, a reduction in average grain size is attributed not only to heterogeneous nucleation but also to the physical growth restriction effect facilitated by the TiB2 particle coating. This study offers insights into leveraging particles that do not participate in heterogeneous nucleation within master alloy-based grain refinement systems.

A new synergy to overcome the strength-ductility dilemma in Al-Si-Cu alloy by adding AlZrNiTi master alloy

With the increase in lightweight components, Al-Si-Cu alloys are extensively applied in the automotive field. In this study, a multi-principal element alloy (MPEA) AlZrNiTi was designed to modify the Al-9Si-3Cu alloy, and the modification effects of individual additions of Zr, Ni, and Ti elements to the alloy were assessed. Moreover, the microstructure evolution, fracture behavior, and the mechanisms of strengthening and toughening during the modification process were investigated. Experimental results showed that when the addition amount of AlZrNiTi alloy was 0.8 wt%, significant refinements were made to the α-Al, eutectic Si, and Al2Cu in the Al-9Si-3Cu alloy, and the mechanical properties were significantly improved. In addition, the AlSiZr phase served as the heterogeneous nucleation core of α-Al was discovered. Furthermore, the AlZiTi phase was enriched at the front edge of the solid-liquid interface in solidification, hindering the growth of α-Al grains. It was also found that Al(Ni, Cu) particles with a size of 336 nm promoted the formation of high-density twins in Si crystal through the impurity-induced twin (IIT) mechanism, thereby modifying the Si phase. Comparative experiments reveal that the modification effect and mechanical properties of AlZrNiTi master adding to Al-9Si-3Cu alloy was obviously better than that of individual adding Zr, Ni, and Ti elements.

Effect of Ni on the mechanical and corrosion properties of TiC-reinforced steel matrix composites

Particle-reinforced steel matrix composites typically lead to a decrease in corrosion resistance while enhancing mechanical properties. However, steel matrix composites for marine applications require superior mechanical properties and corrosion resistance. In this study, 8 vol% TiC/Fe–C composites were prepared using the master alloy method. The effects of Ni contents (0, 1.2 wt%, 1.6 wt%, 2.0 wt%, and 2.4 wt%) on the mechanical and corrosion properties of the composites were evaluated. Results indicated that the tensile strength, elongation, and corrosion resistance of the composites initially increased and then decreased with increasing Ni content. The σUTS and εf of Ni2.0 composites increased from 536 MPa and 4.1 % for Ni0 to 1100 MPa and 9.0 %, respectively. The icorr and corrosion rate of the Ni2.0 composite were 0.440 μA/cm2 and 0.0057 mm/year, respectively. The mechanical properties and corrosion resistance of TiC particle-reinforced steel matrix composites were simultaneously enhanced by the addition of 2.0 wt% Ni. The increase in strength is mainly attributed to changes in thermal mismatch resulting from Ni addition, solid solution strengthening of the Fe–Ni solid solution, and improved interface compatibility between the TiC particles and the matrix, thus enhancing load transfer efficiency. The increase in plasticity can be attributed to the significant improvement in interface deformation compatibility with Ni addition. The increase in corrosion resistance primarily results from the steel matrix alloying, uniform distribution of TiC particles, and strong interface bonding between the particles and the matrix.

On the Role of Al-B Master Alloy and Heat Treatment on Synergistic Improvement in Electrical Conductivity and Hardness of Al-Mg-Si Alloys

On the Role of Al-B Master Alloy and Heat Treatment on Synergistic Improvement in Electrical Conductivity and Hardness of Al-Mg-Si Alloys

A Direct Dry Synthesis Route for High Purity Catalytic Nanoporous Metallic Films

Control of catalyst morphology is important because it affects many catalytic related properties such as, active sites, surface energy, and surface area, which can lead to tunable catalytic activity. Nanoporous metallic networks (NPMs), a morphology of interest for catalysis, contain many uncoordinated atoms at the surface and highly curved ligaments that can have a large effect on catalytic performance. Nanoporous self-supported metal structures have been synthesized in the past by dealloying of a master alloy,[1] which is a wet chemical method. This technique uses an Au-Ag alloy, from which Ag is etched away and which always results in NPMs containing residual amounts of the sacrificial metal (Ag) preventing the formation of high-purity structures. It follows that the catalytic properties of pure NPMs formed by dealloying can not be studied due to metal 'impurities' remaining in the structure. Although these 'impurities' contribute to catalytic activity and stability, it is difficult to control their amount and the systematic investigation of the 'impurity' effect is almost impossible for these NPMs.Here, we present results obtained by using physical vapor deposition, in the form of glancing angle deposition (GLAD), together with plasma etching to form nanoporous ultra-thin metal mesh structures, in a unique and facile dry synthesis method,[2] unlike most wet chemical synthesis methods used to prepare catalysts, which result chemical waste. The nanostructured metal mesh films are suitable for catalysis as they are extremely pure and highly porous, and contain high curvature ligaments, different crystal motifs, and many grain boundaries. We present nanoporous gold films (NPGF) prepared by our method as an example material. We show that the electrochemical structural stability of the NPGF is remarkably higher than that of dealloyed nanoporous gold, which is a result of the high amount of grain boundaries. Furthermore, the electrocatalytic performance of CH3OH oxidation is measured and the results show high catalytic activity for pure NPGF.[3] Our GLAD method can be applied to various metals and enables precise mixing or doping of different materials composing the NPMs. The high porosity, active sites, and potential elemental mixing will lead to new catalysts, especially suitable for CO2 reduction to fuels and value-added chemicals.[1] G. Wittstock, M. Bäumer, W. Dononelli, T. Klüner, L. Lührs, C. Mahr, L. V. Moskaleva, M. Oezaslan, T. Risse, A. Rosenauer, A. Staubitz, J. Weissmüller, A. Wittstock, Chem. Rev. 2023, 123, 6716.[2] H. Kwon, H.-N. Barad, A. R. Silva Olaya, M. Alarcón-Correa, K. Hahn, G. Richter, G. Wittstock, P. Fischer, ACS Appl. Mater. Interfaces 2023, 15, 5620.[3] H. Kwon, H.-N. Barad, A. R. Silva Olaya, M. Alarcón-Correa, K. Hahn, G. Richter, G. Wittstock, P. Fischer, ACS Catal. 2023, 11656.

Effects of nano-micron TiB2-Al2Y particles on the microstructural evolution and mechanical properties of extruded Mg-9Y-0.6La composites

In this study, the nano-micron TiB2-Al2Y/Mg-9Y-0.6La composites were prepared by introducing nano-TiB2 and micron-Al2Y particles into Mg-9Y-0.6La alloys via the addition of nano-TiB2/Al master alloy. The introduction of nano-micron TiB2-Al2Y particles refined the α-Mg grains, weakened the basal texture, and promoted the dynamic recrystallization of the composites. The yield strength and tensile strength of the 4.31 wt% TiB2-Al2Y/Mg-9Y-0.6La composite were increased by 69 MPa and 65 MPa, respectively, compared with the Mg-9Y-0.6La alloy. The main strengthening mechanisms of the composites were fine grain strengthening, Orowan strengthening, and coefficient of thermal expansion strengthening caused by the TiB2-Al2Y particles.

Stability of oxide crucibles and implications for the fabrication of Zr-based bulk metallic glass master alloys

In this study, a systematic evaluation was conducted on the performance of Al2O3, MgO, BaZrO3 and Y2O3 crucibles for melting Zr-based bulk metallic glass master alloys. The interaction between the crucibles and the alloy melts was investigated, focusing on the effect of crucible type and the addition of Y element on the interaction. The results indicated that the relative stability of the evaluated oxide crucibles, in order of decreasing interaction extent, followed the sequence: MgO→Y2O3→Al2O3→BaZrO3. The grading did not follow the free energy data of the formation of these oxides. It was because that the Y combined with O in the alloy melts to form Y2O3 products, which adhered to the inner surface of the crucible. This further prevented the dissolution of the crucible refractory. Among the tested crucibles, the Y2O3 product layer exhibited the most complete structure on the surface of BaZrO3 crucible, thereby minimizing both the corrosion of the crucible and the contamination of the alloy melts.

Preparation of Mg-Nd alloys by in situ reduction using Nd2O3

The high cost of producing magnesium alloys containing rare earth with Mg-RE master alloy severely restricts the wide application of rare earth in magnesium alloys. Consequently, we have adopted a novel, cost-effective approach to preparing magnesium alloys containing rare earth elements by calcium thermal reduction of RE₂O₃. This paper presents the successful preparation of neodymium-containing magnesium alloy by the method described, with the process parameters optimized by orthogonal test and single-factor experiment. The optimum process parameters are 780℃ melting point, 1/6 content ratio of Ca to Nd2O3, and 90 min reaction time. The results of SN ratios and ANOVA showed that time had the greatest effect on Nd yield, the content ratio of Ca and Nd2O3 followed, and temperature had the least effect on Nd yield. The actual Nd yield of the optimal alloy is 32.67 %, which is in the range of Taguchi's prediction of 23.36–33.83 %. Based on orthogonal experiments, the relationship between the three factors and Nd yield was studied separately and in detail. The results show that the Nd yield exhibits a trend of initial increase and subsequent decline as a function of reaction time, content ratio of Ca to Nd2O3, and melting temperature. The Nd yield peaked at a reaction time of 90 min, a content ratio of Ca to Nd2O3 of 1/6 and a melting temperature of 780 ℃. A physical phase analysis and microstructure observation of the alloys prepared with the optimal process parameters were conducted. The alloy is comprised primarily of three distinct phases: α-Mg, Mg2Ca, and Mg41Nd5. This proves that Mg-Nd alloy can be prepared successfully by this method, and provides a new idea for the preparation of magnesium alloys containing rare earth.

Effect of Addition of Ti on Selected Properties of AlSi5Cu2Mg Alloy

The paper focuses on the investigation of the influence of Ti on selected properties of the hypoeutectic aluminium alloy AlSi5Cu2Mg. AlSi5Cu2Mg alloy finds application in the field of production of high-strength cylinder head castings intended for the automotive industry due to the optimal combination of mechanical, physical and foundry properties. In commercial production, the maximum Ti content is limited by the manufacturer (Ti max. = 0.03 wt.%), which significantly limits the possibilities of refinement the alloy with Ti-based grain refiners. Therefore, the possibility of increasing the Ti content beyond the manufacturer's recommendation is considered in this work. The main aim of the work is to evaluate the influence of graded Ti addition (0.1; 0.2; 0.3 wt.% Ti) on the resulting mechanical and physical properties of the AlSi5Cu2Mg alloy. Simultaneously, the influence of increased Ti content on the microstructure of AlSi5Cu2Mg alloy is evaluated. The alloying element was introduced into the melt in the form of AlTi5B1 master alloy. The effect of T6 heat treatment on the resulting mechanical and physical properties and microstructure of the hypoeutectic AlSi5Cu2Mg alloy with graded Ti addition was also investigated in the experimental work.

Transforming Cu into Cu2O/RuAl intermetallic heterojunction for lowering the thermodynamic energy barrier of the CO2 reduction and evolution reactions in Li-CO2 battery

The Li–CO2 battery has been under the spotlight of future battery technologies since it can achieve CO2 utilization and energy conversion simultaneously. However, its advancement is hampered by poor energy efficiency and limited reversibility due to the sluggish kinetics of the CO2 reduction and evolution reactions. Herein, a multiscale nanoporous interpenetrating‑phase nanohybrid of RuAl intermetallic and Cu2O (MP-Cu2O/RuAl) was carved by driving synchronous phase and microstructure evolutions through dealloying of one RuCuAl master alloy. The built-in RuAl intermetallic and Cu2O closely stack to form abundant nano-interfaces with revolutionized electronic structure. The theoretical simulations reveal that the Cu2O/RuAl interface can distinctly reduce the energy barrier of the Li2CO3 decomposition reaction. The interconnected pore channels with large surface area can enhance catalytic site accessibility, mass transfer, and uniform deposition of the discharge products. In situ differential electrochemical mass spectrometry discloses that the CO2-to-electron ratio during charging coincides with the theoretical value of 3/4, demonstrating the high efficacy of MP-Cu2O/RuAl in achieving the recycling of CO2. The dealloying protocol provides an affordable platform to empower transition metal oxides into high-efficiency electrocatalysts by hybridizing with metallic nano-sponge for advancing the application of Li–CO2 batteries.

Microstructure and Mechanical Properties of Mg-Al-La-Mn Composites Reinforced by AlN Particles.

The Mg-Al-RE series heat-resistant magnesium alloys are applied in automotive engine and transmission system components due to their high-temperature performance. However, after serving at a high temperature for a long time, the Al11RE3 phase coarsened and even decomposed, while the Mg17Al12 phase grew and dissolved, which limits the service temperature of Mg-Al-RE series heat-resistant magnesium alloys to a maximum of 175 °C. In this study, a new preparation method for in situ AlN particles was presented. The AlN/Mg-4Al-4La-0.3Mn composites were prepared by a master alloy and casting method. The effects of various contents of AlN (0.5-3.0 wt.%) on the microstructure and mechanical properties of the Mg-4Al-4La-0.3Mn (AE44) alloy at room (25 °C) and high temperatures (150-250 °C) were investigated. Microstructure analysis revealed that the inclusion of AlN led to a reduction in both the grain size and second phase size in the AE44 alloy, while also improving the distribution of the second phase. The average grain size, Al11La3 phase, Al2La phase, and Al3La phase of the 2.0 wt.% AlN/AE44 composite were 135.7, 9.6, 1.9, and 12.6 μm, respectively, which were significantly lower than those of the AE44 matrix alloy (179.8, 12.6, 3.3, 17.8 μm). The refinement was attributed to the ability of AlN particles to serve as heterogeneous nucleation cores for α-Mg and, at the same time, impede the growth of the solid-liquid interface, eventually leading to grain refinement. With the increase in the AlN content, the mechanical properties of composites initially exhibited an increase at both room and high temperatures, followed by a subsequent decrease. When the AlN content was 2.0 wt.%, the composite exhibited optimal strength and plasticity matching. At room temperature, the TYS, UTS, and EL values of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite were 96 MPa, 175 MPa, and 7.0%, respectively, which were increased by 26 MPa, 27 MPa, and 0.7% when compared with the base alloy. The TYS of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite at 150 °C, 200 °C, and 250 °C were 17 MPa, 14 MPa, and 22 MPa higher than those of the matrix alloy, respectively. The main strengthening mechanisms were second phase strengthening, load transfer strengthening, and thermal mismatch strengthening. At elevated temperatures, AlN particles effectively pinned the grain boundaries, inhibiting their migration, and hindered dislocation climbing, resulting in excellent mechanical properties of the composites at high temperatures. This study contributes to the advancement of in situ AlN particle preparation methods and the exploration of effects of AlN on the properties and microstructure of Mg-Al-RE alloys at high temperatures (150-250 °C).

Composition and Structure of Surface Layer in Composite Castings from Gray Cast Iron Formed Using Chromium-Ferroboron Master Alloys

Composition and Structure of Surface Layer in Composite Castings from Gray Cast Iron Formed Using Chromium-Ferroboron Master Alloys

Hot Deformation Constitutive Analysis and Processing Maps of Ultrasonic Melt Treated A5052 Alloy.

Hot deformation constitutive analysis and processing maps of ultrasonic melt treated (UST) A5052 alloy were carried out based on a hot torsion test in this study. The addition of the Al-Ti master alloy as a grain refiner with no UST produced a finer grain size than the UST and pure Ti sonotrode. The Al3Ti phase particles in the case of the Al-10Ti master alloy acted as a nucleus for grain refinement, while the Ti atoms dissolved in the melt from the sonotrode were considered to have less of a grain refinement effect, even under UST conditions, than the Al3Ti phase particles in the Al-Ti master alloy. The constitutive equations for each experimental condition by torsion test were derived. In the processing maps examined in this study, the flow instability region was not present under UST in the as-cast condition, but it existed under the no UST condition. The effects of UST examined in this study are considered as (i) the uniform distribution of Ti solutes from the sonotrode and (ii) the reduction of pores by the degassing effect. After the homogenization heat treatment, most instability regions disappeared because the microstructures became uniform following the decomposition of intermetallic compounds and distribution of solute elements.

Study on microstructure and refining effect of deformed Al-4.5Er-1Zr-1.5Ti master alloy

The microstructure and grain refinement of Al-4.5Er-1Zr-1.5Ti master alloy were analyzed by the refinement experiment, OM, SEM and XRD. The results show that the grain size of pure aluminum is reduced from 14,000μm to 202μm by Al-4.5Er-1Zr-1.5Ti master alloy, which is mainly due to the nucleation promoted by Ti2Al20Er, Al3Er and Al3Ti. Plastic deformation further improves the refining effect of the material by improving the primary phase size, and the Al-4.5Er-1Zr-1.5Ti −2ARB can refine the pure aluminum from 202 mμm to 150μm, and the refinement was increased by 25.7 %. The master alloy showed a better refinement effect in Al-5Cu alloy than pure aluminum, with a grain size of 92μm and a refinement improvement of 97.8 %.