Grain refining by ultrasonic stirring of the weld pool
TL;DR: In this paper, an ultrasonic grain refining method was proposed to improve the mechanical properties and solidification-cracking resistance of arc welds of Mg alloys AZ31 Mg and AZ91 Mg.
About: This article is published in Acta Materialia.The article was published on 2016-03-01 and is currently open access. It has received 115 citations till now. The article focuses on the topics: Weld pool.
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TL;DR: In this article, the authors identified the materials processing challenges in wire-arc additive manufacturing (WAAM), including high residual stresses, undesirable microstructures, and solute segregation and phase transformations at solidification.
Abstract: Wire Arc Additive Manufacturing (WAAM) is attracting significant attention in industry and academia due to its ability to capture the benefits of additive manufacturing for production of large components of medium geometric complexity. Uniquely, WAAM combines the use of wire and electric arc as a fusion source to build components in a layer-by-layer approach, both of which can offer significant cost savings compared to powder and alternative fusion sources, such as laser and electron beam, respectively. Meanwhile, a high deposition rate, key for producing such components, is provided, whilst also allowing significant material savings compared to conventional manufacturing processes. However, high quality production in a wide range of materials is limited by the elevated levels of heat input which causes a number of materials processing challenges in WAAM. The materials processing challenges are fully identified in this paper to include the development of high residual stresses, undesirable microstructures, and solute segregation and phase transformations at solidification. The thermal profile during the build poses another challenge leading to heterogeneous and anisotropic material properties. This paper outlines how the materials processing challenges may be addressed in WAAM by implementation of quality improving ancillary processes. The primary WAAM process selections and ancillary processes are classified by the authors and a comprehensive review of their application conducted. Strategies by which the ancillary processes can enhance the quality of WAAM parts are presented. The efficacy and suitability of these strategies for versatile and cost effective WAAM production are discussed and a future vision of WAAM process developments provided.
392 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
Cites background or methods from "Grain refining by ultrasonic stirri..."
...Magnetic arc oscillation for microstructural refinement of the fusion zone was nicely exemplified by the works of Kou’s group [122,125,161] in gas tungsten arc welding of Al and Mg alloys....
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...used ultrasonic stimuli to refine the fusion zone microstructure of two Mg alloys, AZ31 and AZ91 [161]....
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...More recently, Yuan et al. used ultrasonic stimuli to refine the fusion zone microstructure of two Mg alloys, AZ31 and AZ91 [161]....
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...For example, in AZ31 Mg alloys, it has been shown that equiaxed grains can grow into columnar ones, while such has not been observed for AZ91 Mg alloys [122]....
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...Some works [130,161,276] have addressed the use of ultrasonic vibration during fusion-based welding....
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TL;DR: The authors combine ultrasound and 3D printing to promote equiaxed and refined microstructures in a titanium alloy and a nickel-based superalloy resulting in improved mechanical properties.
Abstract: Additive manufacturing (AM) of metals, also known as metal 3D printing, typically leads to the formation of columnar grain structures along the build direction in most as-built metals and alloys. These long columnar grains can cause property anisotropy, which is usually detrimental to component qualification or targeted applications. Here, without changing alloy chemistry, we demonstrate an AM solidification-control solution to printing metallic alloys with an equiaxed grain structure and improved mechanical properties. Using the titanium alloy Ti-6Al-4V as a model alloy, we employ high-intensity ultrasound to achieve full transition from columnar grains to fine (~100 µm) equiaxed grains in AM Ti-6Al-4V samples by laser powder deposition. This results in a 12% improvement in both the yield stress and tensile strength compared with the conventional AM columnar Ti-6Al-4V. We further demonstrate the generality of our technique by achieving similar grain structure control results in the nickel-based superalloy Inconel 625, and expect that this method may be applicable to other metallic materials that exhibit columnar grain structures during AM. 3D printing of metals produces elongated columnar grains which are usually detrimental to component performance. Here, the authors combine ultrasound and 3D printing to promote equiaxed and refined microstructures in a titanium alloy and a nickel-based superalloy resulting in improved mechanical properties.
345 citations
TL;DR: In this article, a systematic in-depth analysis of diversified aspects of ultrasonic application in metal joining and processing including its limitations, future prospects and assessments are classified and discussed, and detailed state-of-the art, experimentation and progresses of the ultrasonic vibrations and its applications in the above areas are comprehensively examined, evaluated and presented for exhaustive understandings of its physical mechanism.
177 citations
TL;DR: A review of the current status of additive manufacturing with Al-alloys is presented in this paper, focusing on the microstructural characteristics and how these influence mechanical properties, and the remaining challenges in the development of AM with high-strength Al-aloys are discussed.
Abstract: Additive manufacturing (AM) of metallic alloys for structural and functional applications has attracted significant interest in the last two decades as it brings a step change in the philosophy of design and manufacturing. The ability to design and fabricate complex geometries not amenable to conventional manufacturing, and the potential to reduce component weight without compromising performance, is particularly attractive for aerospace and automotive applications. This has culminated in rapid progress in AM with Ti- and Ni-based alloys. In contrast, the development of AM with Al-alloys has been slow, despite their widespread adoption in industry owing to an excellent combination of low density and high strength-to-weight ratio. Research to date has focused on castable and weldable AlSiMg-based alloys (which are less desirable for demanding structural applications), as well as on the development of new AM-specific AlMgSc alloys (based on 5xxx series). However, high strength wrought Al-alloys have typically been unsuitable for AM due to their unfavourable microstructural characteristics under rapid directional solidification conditions. Nevertheless, recent research has shown that there is promise in overcoming the associated challenges. Herein, we present a review of the current status of AM with Al-alloys. We primarily focus on the microstructural characteristics, and on exploring how these influence mechanical properties. The current metallurgical understanding of microstructure and defect formation in Al-alloys during AM is discussed, along with recent promising research exploring various microstructural modification methodologies. Finally, the remaining challenges in the development of AM with high-strength Al-alloys are discussed.
117 citations
References
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Book•
01 Jan 1981TL;DR: In this article, the authors discuss the properties of phase diagrams for single-component systems, including the influence of interfaces on the equilibrium of binary solutions in Heterogeneous Systems (Heterogeneous Binary Phase Diagrams).
Abstract: Thermodynamics and Phase Diagrams Equilibrium Single-Component Systems Binary Solutions Equilibrium in Heterogeneous Systems Binary Phase Diagrams Influence of Interfaces on Equilibrium Ternary Equilibrium Additional Thermodynamic Relationships for Binary Solutions Computation of Phase Diagrams Kinetics of Phase Transformations Exercises References Further Readings Diffusion Atomic Mechanisms of Diffusion Interstitial Diffusion Substitutional Diffusion Atomic Mobility Tracer Diffusion in Binary Alloys Diffusion in Ternary Alloys High-Diffusivity Paths Diffusion in Multiphase Binary Systems Exercises References Further Readings Crystal Interfaces and Microstructure Interfacial Free Energy Solid=Vapor Interfaces Boundaries in Single-Phase Solids Interphase Interfaces in Solids Interface Migration Exercises References Further Readings Solidification Nucleation in Pure Metals Growth of a Pure Solid Alloy Solidification Solidification of Ingots and Castings Solidification of Fusion Welds Solidification during Quenching from the Melt Metallic Glasses Case Studies of Some Practical Castings and Welds Exercises References Further Readings Diffusional Transformations in Solids Homogeneous Nucleation in Solids Heterogeneous Nucleation Precipitate Growth5 Overall Transformation Kinetics-TTT Diagrams Precipitation in Age-Hardening Alloys Precipitation of Ferrite from Austenite Cellular Precipitation Eutectoid Transformations Massive Transformations Ordering Transformations Case Studies Exercises References Further Readings Diffusionless Transformations Characteristics of Diffusionless Transformations Martensite Crystallography Theories of Martensite Nucleation Martensite Growth1 Premartensite Phenomena Tempering of Ferrous Martensites Case Studies Exercises References Further Readings Solutions to Exercises Compiled by John C. Ion
4,104 citations
Book•
15 Jan 1964
TL;DR: Solidification is the process by which a liquid is transformed into a crystalline solid as discussed by the authors, in which the solid that forms first is solvent rich as distinct from crystallisation, and the crystals that are formed are solute rich.
Abstract: Solidification, in the sense used in this context, is the process by which a liquid is transformed into a crystalline solid. In crystal growth the solid that forms first is solvent rich as distinct from crystallisation, in which the crystals that are formed are solute rich. It is not always possible to make a clear distinction. Solidification is important as the process employed in the widely used process of casting, in all its forms from large ingots of steel to small crystals of silicon. While in principle it would seem simple to convert a homogeneous liquid into an equally homogeneous perfect crystal, this is extremely difficult, if not impossible to achieve in practice. Thorough understanding requires that the process be studied at various levels, which can be conveniently described as the angstrom level, the micron level and the centimetre level.
1,359 citations
TL;DR: In this article, an analysis for the growth of equiaxed grains ahead of the columnar front during directional solidification is presented, and the model considers both single-phase and eutectic growth.
1,062 citations
TL;DR: In this paper, a grain refinement model was developed for aluminum alloys, which took into account both alloy chemistry and nucleant particle potency, and was applied to experimental data for a range of magnesium alloys.
Abstract: The literature on grain refinement of magnesium alloys is reviewed with regard to two broad groups of alloys: alloys that contain aluminum and alloys that do not contain aluminum. The alloys that are free of aluminum are generally very well refined by Zr master alloys. On the other hand, the understanding of grain refinement in aluminum bearing alloys is poor and in many cases confusing probably due to the interaction between impurity elements and aluminum in affecting the potency of nucleant particles. A grain refinement model that was developed for aluminum alloys is presented, which takes into account both alloy chemistry and nucleant particle potency. This model is applied to experimental data for a range of magnesium alloys. It is shown that by using this analytical approach, new information on the refinement of magnesium alloys is obtained as well as providing a method of characterizing the effectiveness of new refiners. The new information revealed by the model has identified new directions for further research. Future research needs to focus on gaining a better understanding of the detailed mechanisms by which refinement occurs and gathering data to improve our ability to predict grain refinement for particular combinations of alloy and impurity chemistry and nucleant particles.
598 citations
06 May 1998
TL;DR: In this article, the authors present a history of Ultrasonic applications in metallurgical applications and provide a detailed overview of the development and application of ultrasonic processes in the field of metallurgy.
Abstract: Preface Authors Historical Overview of Ultrasonic Applications to Metallurgy References Fundamentals of Ultrasonic Melt Processing Dynamic Means of Melt Processing Low-Frequency Vibrations and Ultrasound: Basic Equations Propagation of Acoustic Waves in the Melt Acoustic Cavitation in Liquid Metals Cavitation Strength of Liquids Cavity Dynamics Cavitation Region in Liquids Acoustic Flows Experimental Studies of Cavitation in Liquid Metals Sonoluminescence in Melts Accelerated Mixing and Dissolution of Components in the Melt References Ultrasonic Degassing Cavitation and Degassing Nuclei Mechanism of Ultrasonic Degassing Ultrasonic Degassing in a Stationary Volume Ultrasonic Degassing in the Flow References Ultrasonic Filtration Effect of Ultrasound on Surface Tension and Wetting Sonocapillary Effect Basics of Filtration Mechanism of Ultrasonic Melt Filtration Filtering through Multilayer Screen Filters: Usfirals Process References Ultrasonic Grain Refinement Mechanisms of Ultrasonic Grain Refinement Activation of Substrates Deagglomeration and Dispersion of Particles Refinement of Nucleating Intermetallics Dendrite Fragmentation Nondendritic Solidification Ultrasonic Melt Processing in the Mold Ultrasonic Melt Processing in the Melt Flow References Refinement of Primary Particles Formation of Primary Particles during Solidification Effect of Ultrasound on Solidification of Intermetallic Compounds Effect of Ultrasound on the Solidification of Hypereutectic Al-Si Alloys References Ultrasonic Processing during Direct-Chill Casting of Light Alloys Direct-Chill Casting of Aluminum Alloys Ultrasonic Processing in the Sump of a Billet Ultrasonic Melt Processing in the Launder Direct-Chill Casting of Magnesium Alloys Effect of Ultrasonic Degassing and Filtration on Structure and Properties of Wrought Products Ultrasonic Degassing Ultrasonic Filtration Effect of Nondendritic Structure on Structure and Properties of Wrought Products Aluminum Wrought Alloys Magnesium Wrought Alloys Effect of Nondendritic Grain Structure on Homogenization References Ultrasonic Melt Processing during Shape Casting of Light Alloys Technological Approaches to Shape Casting with Ultrasonic Processing Effects of Ultrasonic Processing on Solidification in Molds Effect of Ultrasonic Processing on Structure and Properties of Shape Castings References Ultrasonic Processing of Composite and Immiscible Alloys Ultrasound-Assisted Introduction of Nonmetallic Particles and Fibers to Liquid Metals Mechanical Properties of Composite Materials Produced Using Ultrasonic Processing Ultrasonic Processing of Immiscible Alloys and Metallic Emulsions References Rapid Ultrasonic Solidification of Aluminum Alloys Basic Sonication Schemes for Rapid Solidification Formation of Nondendritic Structure in Rapid Solidification Mechanical Properties of Wrought Products from Nondendritic Granules References Zone Refining of Aluminum with Ultrasonic Melt Processing Basics of Zone Refining Ultrasonic Zone Refining of Aluminum Mechanisms of Sonication Effects on Zone Refining Structure and Characteristics of Deformed Acoustically Refined Aluminum References Semisolid Deformation of Billets with Nondendritic Structure Introduction to Semisolid Deformation 291 Effect of Nondendritic Structure of Billets on Thixotropic Behavior of Aluminum Alloys Rheological Parameters of Semisolid Alloys Computer Simulation of Semisolid Forging Semisolid Deformation of Casting Alloys with Nondendritic Grain Structure Application of Ultrasonic Processing to Rheocasting References Ultrasonic Melt Processing: Practical Issues Ultrasonic Equipment Design of Waveguide and Sonotrode Selection of Materials for Sonotrodes Characterization of Ultrasonic Processing References
532 citations