A Review on Additive Manufacturing of Titanium Alloys for Aerospace Applications: Directed Energy Deposition and Beyond Ti-6Al-4V
TL;DR: In this article, the authors focus on the processing-microstructure-property relationships in the DED-processed titanium alloys (Ti-6Al-4V and beyond) with the following aspects: (1) microstructure evolution induced by solidification, thermal cycles, and post-processing heat treatment; (2) tensile properties of as-deposited and heat-treated titanium alloy; (3) defects, residual stresses, and fatigue properties; and (4) micro/nanomechanical properties.
Abstract: Titanium alloys are expensive and difficult to process into large complex components for aerospace applications. Directed energy deposition (DED), one of the additive manufacturing (AM) technologies, offers a high deposition rate, being suitable for fabricating large metallic components. So far, most review articles on the AM of titanium discuss the popular powder bed fusion method with the emphasis on the “workhorse” titanium alloy—Ti-6Al-4V. There have been few review articles on the DED process of a broad range of titanium alloys—near-α, β, and other α + β alloys beyond Ti-6Al-4V. This article focuses on the processing–microstructure–property relationships in the DED-processed titanium alloys (Ti-6Al-4V and beyond) with the following aspects: (1) microstructure evolution induced by solidification, thermal cycles, and post-processing heat treatment; (2) tensile properties of as-deposited and heat-treated titanium alloys; (3) defects, residual stresses, and fatigue properties; and (4) micro/nanomechanical properties. The article concludes with perspectives about future directions in this field.
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TL;DR: The most common metal additive manufacturing (AM) methods in use include Powder Bed Fusion, Directed Energy Deposition, and various solid-state processes as mentioned in this paper , which encapsulates the myriad of manufacturing processes available to meet industrial needs.
Abstract: Abstract Metal additive manufacturing (AM) encapsulates the myriad of manufacturing processes available to meet industrial needs. Determining which of these AM processes is best for a specific aerospace application can be overwhelming. Based on the application, each of these AM processes has advantages and challenges. The most common metal AM methods in use include Powder Bed Fusion, Directed Energy Deposition, and various solid-state processes. Within each of these processes, there are different energy sources and feedstock requirements. Component requirements heavily affect the process determination, despite existing literature on these AM processes (often inclusive of input parameters and material properties). This article provides an overview of the considerations taken for metal AM process selection for aerospace components based on various attributes. These attributes include geometric considerations, metallurgical characteristics and properties, cost basis, post-processing, and industrialization supply chain maturity. To provide information for trade studies and selection, data on these attributes were compiled through literature reviews, internal NASA studies, as well as academic and industry partner studies and data. These studies include multiple AM components and sample build experiments to evaluate (1) material and geometric variations and constraints within the processes, (2) alloy characterization and mechanical testing, (3) pathfinder component development and hot-fire evaluations, and (4) qualification approaches. This article summarizes these results and is meant to introduce various considerations when designing a metal AM component.
25 citations
TL;DR: In this paper, high-speed nanoindentation mapping, electron probe microanalysis, and electron backscatter diffraction were employed to characterize as-deposited and heat-treated Ti-6Al-2Zr-Mo-V alloys.
Abstract: Titanium alloys are widely used in additive manufacturing, but their complex microstructures and related micromechanical properties have not been fully explored. Here, we employ high-speed nanoindentation mapping, electron probe microanalysis, and electron backscatter diffraction to characterize as-deposited and heat-treated Ti–6Al–2Zr–Mo–V alloys. Our results show the correlations between mechanical contrasts (hardness and elastic modulus) and phase contrasts (α and β). The hardness and elastic modulus of the α and β phases are increased due to the element redistribution after annealing (Al diffuses from β to α; Mo and V diffuse from α to β). We use a K-means clustering algorithm to analyze the nanoindentation dataset and correlate the mechanical property maps to the distribution of α and β phases. Our study employs the emerging high-speed nanoindentation mapping to give a better understanding of the microstructure–mechanical property relationship of additive manufactured multiphase alloys across length scales.
25 citations
TL;DR: The influence of post-AM heat treatment on microstructure, mechanical properties, and corrosion behavior of the major categories of AM metals including steel, Ni-based superalloys, Al alloys, Ti alloys and high entropy alloys is discussed in this paper .
21 citations
TL;DR: In this article, high-resolution scanning electron microscope (SEM) and high-speed nanoindentation are employed to characterize the microstructure and mechanical properties of the transition zone from the Ti2AlNb substrate (disk) to the γ-TiAl alloy (blade).
20 citations
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TL;DR: In this paper, the authors describe the complex relationship between additive manufacturing processes, microstructure and resulting properties for metals, and typical microstructures for additively manufactured steel, aluminium and titanium are presented.
2,837 citations
15 Aug 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance as discussed by the authors.However, titanium usage is strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels.
Abstract: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance. Titanium usage is, however, strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels. Hence the advantages of using titanium must be balanced against this added cost. The titanium alloys used for aerospace applications, some of the characteristics of these alloys, the rationale for utilizing them, and some specific applications of different types of actual usage, and constraints, are discussed as an expansion of previous reviews of β alloy applications. [1,2]
1,938 citations
TL;DR: In this paper, the complexity and variety of fundamental phenomena in this material system with a focus on phase transformations and mechanical behaviour are discussed. And the challenges that lie ahead in achieving these goals are delineated.
1,797 citations
TL;DR: In this article, the authors investigated the anisotropic mechanical properties of a Ti-6Al-4V three-dimensional cruciform component fabricated using a directed energy deposition additive manufacturing (AM) process.
983 citations
TL;DR: A broad range of metal additive manufacturing (AM) technologies and reviews literatures on the anisotropy and heterogeneity of microstructure and mechanical properties for metal AM parts are presented in this paper.
799 citations