Additive manufacturing of metals: a brief review of the characteristic microstructures and properties of steels, Ti-6Al-4V and high-entropy alloys (original) (raw)
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Additive manufacturing of steels: a review of achievements and challenges
Journal of Materials Science, 2020
Metal additive manufacturing (AM), also known as 3D printing, is a disruptive manufacturing technology in which complex engineering parts are produced in a layer-by-layer manner, using a high-energy heating source and powder, wire or sheet as feeding material. The current paper aims to review the achievements in AM of steels in its ability to obtain superior properties that cannot be achieved through conventional manufacturing routes, thanks to the unique microstructural evolution in AM. The challenges that AM encounters are also reviewed, and suggestions for overcoming these challenges are provided if applicable. We focus on laser powder bed fusion and directed energy deposition as these two methods are currently the most common AM methods to process steels. The main foci are on austenitic stainless steels and maraging/precipitation-hardened (PH) steels, the two so far most widely used classes of steels in AM, before summarising the state-of-the-art of AM of other classes of steels...
Metal Fabrication by Additive Manufacturing Using Laser and Electron Beam Melting Technologies
Journal of Materials Science & Technology, 2012
Selective laser melting (SLM) and electron beam melting (EBM) are relatively new rapid, additive manufacturing technologies which can allow for the fabrication of complex, multi-functional metal or alloy monoliths by CAD-directed, selective melting of precursor powder beds. By altering the beam parameters and scan strategies, new and unusual, even non-equilibrium microstructures can be produced; including controlled microstructural architectures which ideally extend the contemporary materials science and engineering paradigm relating structure-properties-processing-performance. In this study, comparative examples for SLM and EBM fabricated components from pre-alloyed, atomized precursor powders are presented. These include Cu, Ti-6Al-4V, alloy 625 (a Ni-base superalloy), a Co-base superalloy, and 17-4 PH stainless steel. These systems are characterized by optical metallography, scanning and transmission electron microscopy, and X-ray diffraction.
Metallic Additive Manufacturing
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2022
As metallic additive manufacturing grew in many areas, many users have requested greater control over the systems, namely the ability to change the process parameters. The goal of this paper is to review the effects of major process parameters on the quality such as porosity, residual stress, and composition changes and materials properties like microstructure and microsegregation. In this article, we give an overview over the different kinds of metals specially steels in additive manufacturing processes and present their microstructures, their mechanical and corrosion properties, and their heat treatments and their application. Our aim is to detect the microstructures as well as the mechanical and electrochemical properties of metals specially the steels. Steels are subjected during additive manufacturing processing to time-temperature profiles which are very different from the conventional process. We do not describe in detail the additive manufacturing process parameters required to achieve dense parts. We discuss the impact of process parameters on the microstructure, where necessary. I.
Steels in additive manufacturing: A review of their microstructure and properties
Materials Science & Engineering A, 2020
Today, a large number of different steels are being processed by Additive Manufacturing (AM) methods. The different matrix microstructure components and phases (austenite, ferrite, martensite) and the various precipitation phases (intermetallic precipitates, carbides) lend a huge variability in microstructure and properties to this class of alloys. This is true for AM-produced steels just as it is for conventionally-produced steels. However, steels are subjected during AM processing to time-temperature profiles which are very different from the ones encountered in conventional process routes, and hence the resulting microstructures differ strongly as well. This includes a very fine and highly morphologically and crystallographically textured microstructure as a result of high solidification rates as well as non-equilibrium phases in the as-processed state. Such a microstructure, in turn, necessitates additional or adapted post-AM heat treatments and alloy design adjustments. In this review, we give an overview over the different kinds of steels in use in fusion-based AM processes and present their mi-crostructures, their mechanical and corrosion properties, their heat treatments and their intended applications. This includes austenitic, duplex, martensitic and precipitation-hardening stainless steels, TRIP/TWIP steels, maraging and carbon-bearing tool steels and ODS steels. We identify areas with missing information in the literature and assess which properties of AM steels exceed those of conventionally-produced ones, or, conversely, which properties fall behind. We close our review with a short summary of iron-base alloys with functional properties and their application perspectives in Additive Manufacturing. The main advantages of additive manufacturing (AM) technologies of metallic parts compared to conventional synthesis and shaping pro- cesses lie in their ability to produce complex and/or customized parts with a short lead time, albeit in relatively low numbers. These advan- tages are exploited for example when patient-specific implants are produced, when complex, structurally optimized parts lead to performance-critical weight savings, or when AM is used for the repair of expensive metallic jet engine parts. The alloys usually envisaged in these applications are biocompatible, high temperature and lightweight materials such as Ti-, Ni-, Al- and Mg-based alloys. Consequently, re- views of alloys in AM have typically focussed on these materials [1–3], with two notable exceptions which do discuss steels, however with a different focus than the present review [4,5]. Yet, the most successful of all alloy families since the dawn of the iron-age 3000 years ago, namely steel, has received relatively little attention with respect to providing a holistic view of the interplay of alloy design, microstructure, properties and AM processing.
Metal Additive Manufacturing: A Review of Mechanical Properties
Annual Review of Materials Research, 2016
This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when availab...
Additive Manufacturing of Steel Alloys Using Laser Powder-Bed Fusion
Advanced Materials and Processes, 2015
Studying the additive manufacturing of AISI 420 stainless steel and AISI 4140 steel using a laser powder bed-fusion (L-PBF) process helped develop the corresponding process windows regarding the structural integrity of coupons, where systematic defects such as lack of fusion and porosity were minimized. In both cases (AISI 420 and AISI 4140), densities exceeding 99% theoretical were produced. Through precise control of the L-PBF parameters, it is possible to produce the desired shape of martensitic stainless steel grade 420 with an acceptable microstructure and hardness values. A heat treatment cycle that results in the formation of a fine martensite microstructure with precipitation of spheroidal carbides was designed and implemented. Initial studies of the microstructure reveal a relationship between the formation of an ultra-fine microstructure and improved mechanical properties in AISI 4140.
Review on direct metal laser deposition manufacturing technology for the Ti-6Al-4V alloy
The International Journal of Advanced Manufacturing Technology, 2020
Direct laser metal deposition (DLMD) is a breaking edge laser-based additive manufacturing (LAM) technique with the possibility of changing the perception of design and manufacturing as a whole. It is well suitable for building and repairing applications in the aerospace industry which usually requires high level of accuracy and customization of parts; this technique enables the fabrication of materials known to pose difficulties during processing such as titanium alloys. Ti-6Al-4V, which is the most employed titanium-based alloy is one of the materials that are most explored for additive manufacturing process. However, this process is currently at its pioneer stage and very little is known about the fundamental metallurgy and physio-chemical basis that govern the process. Currently, the major problems faced in additive manufacturing include evolution of residual stresses leading to deformed parts and formation of defects such as pores and cracks which are detrimental to the quality of deposits. The presence of these unwanted defects on additively manufactured parts depends on the complex mechanisms taking place in the melt pool during melting, cooling, and solidification which are dependent on processing variables. In addition, during fabrication, some feedstock powder does not melt and thus does not make up part of the final product. The present text entails classification of LAM technologies, operational principles of DLMD, feedstock quality requirements, material laser interaction mechanism, and metallurgy of Ti-6AL-4V alloy.
Materials
Complex structures can now be manufactured easily utilizing AM technologies to meet the pre-requisite objectives such as reduced part numbers, greater functionality, and lightweight, among others. Polymers, metals, and ceramics are the few materials that can be used in AM technology, but metallic materials (Magnesium and Aluminum) are attracting more attention from the research and industrial point of view. Understanding the role processing parameters of laser-based additive manufacturing is critical to maximize the usage of material in forming the product geometry. LPBF (Laser powder-based fusion) method is regarded as a potent and effective additive manufacturing technique for creating intricate 3D forms/parts with high levels of precision and reproducibility together with acceptable metallurgical characteristics. While dealing with LBPF, some degree of porosity is acceptable because it is unavoidable; hot ripping and cracking must be avoided, though. The necessary manufacturing o...
Advances in Metal Additive Manufacturing
Woodhead Publishing, 2022
Advances in Metal Additive Manufacturing explains fundamental information and the latest research on new technologies, including powder bed fusion, direct energy deposition using high energy beams, and hybrid additive and subtractive methods. This book introduces readers to the technology, provides everything needed to understand how the different stages work together, and inspires to think beyond traditional metal processing to capture new ideas in metal. Chapters offer an introduction on metal additive manufacturing, processes, and properties and standards and then present surveys on the most significant international advances in metal additive manufacturing. Throughout, the book presents a focus on the effect of important process parameters on the microstructure, mechanical properties and wear behavior of additively manufactured parts.