Advances in Manufacturing for Aerospace Alloys

The turning operation is one of the oldest conventional processes utilized for manufacturing parts in the aerospace industry. This process configuration is ideal for producing symmetrical parts used in various rotating machines and engines within the aerospace sector. Materials commonly employed in aerospace applications typically possess high strength-to-weight ratios. Certain mechanical properties, such as fatigue life, are dependent on the surface quality achieved during the manufacturing process. Surface roughness and microstructure are influenced by the heat generated due to cutting forces and the cooling rate of the coolant/lubrication system. Selecting process parameters is a crucial and multiobjective optimization decision, where factors such as tool cost, machining time, and surface quality determine the target outcome. Numerous research studies have been conducted on the turning operation, each contributing to a better understanding of its mechanics. Among the different materials used in aerospace, aluminum and titanium alloys are the most common and appropriate due to their high strength-to-weight ratios. This chapter aims to provide a comprehensive overview of process parameter selection for these alloys and the main challenges associated with variable selection. A discussion on the formation of built-up layer (BUL) and built-up edge (BUE) in soft materials is included. In addition, the importance of utilizing proper cooling systems, such as minimum quantity lubrication and high-pressure cooling systems, is emphasized.

High-speed machining (HSM) is a common technique used in the aerospace industry to improve efficiency, achieve high precision, and provide an ability to handle challenging materials effectively. In simple words, it is characterized by high machining speeds and significant performance improvements. Some of the most widespread aerospace alloys such as AA7050, AA7075, Ti-6Al-4V, and Inconel 718 are machined using HSM. However, despite its benefits, there are still various challenges associated with the increased performance. Such challenges include reducing tool wear, managing machining temperatures, enhancing surface quality, improving the predictions of the machining behavior, optimizing the machining parameters, and increasing sustainability. Recent research in aluminum alloys has primarily focused on parameter optimization, improving numerical simulations, advances in cooling methods, and process predictions. In the recent studies involving difficult-to-cut alloys Ti-6Al-4V and Inconel 718, the focus was more on tool wear, cooling methods, choice of tools and coatings, machining mechanisms and their predictions, and the application of new techniques such as vibration and hybrid machining. This chapter provides an overview of HSM technology and the aforementioned recent developments in its utilization in the aerospace industry.

This chapter offers an insightful examination of the advancements in machining aerospace materials, focusing on ultrasonic vibration-assisted (UVA) machining and minimum quantity lubrication (MQL) techniques. It begins with an introduction to the unique challenges associated with machining these advanced materials and how UVA machining and MQL have emerged as innovative solutions to address these challenges. The chapter then systematically explores the effects of these techniques on various aspects of the machining process. It discusses how UVA machining and MQL influence cutting forces, leading to potential reductions in tool wear and energy consumption. The impact on surface quality is also examined, highlighting improvements in terms of both physical appearance and structural integrity. The chapter further discusses the changes in chip morphologies that result from employing UVA machining and MQL, which are crucial for understanding the material removal mechanisms and overall machining efficiency. Finally, it addresses the implications of these techniques on tool wear, emphasizing their potential to extend tool life and maintain machining accuracy. This chapter not only synthesizes current research but also provides practical insights for industry professionals seeking to optimize machining processes for aerospace materials.

Smart electrical discharge machining (EDM), the integration of artificial intelligence (AI) into EDM in aerospace engineering, signifies a transformative leap that offers unprecedented precision, efficiency, and adaptability. This integration involves learning algorithms, real-time decision-making, predictive insights, and adaptive optimization and fostering enhanced precision, efficiency overhaul, cost reduction, and versatility in complexity. Notable studies showcase the evolution of AI-driven smart EDM, utilizing techniques such as artificial neural networks (ANN), adaptive neuro-fuzzy inference system (ANFIS), convolutional neural networks (CNN), deep neural networks (DNN), and support vector regression (SVR), for optimizing critical parameters in aerospace alloy machining. A comprehensive case study on smart wire EDM workpiece height estimation highlights the experimental validation of AI integration, employing CNN for accurate predictions. Results indicate an overall accuracy of 86% in estimating workpiece height across different classes. Future prospects include exploring alternative sensors, real-time monitoring, and multisensor fusion, promising to elevate precision manufacturing in aerospace engineering. In conclusion, smart EDM, with the integration of AI, represents technological convergence and charts a transformative journey that reshapes the landscape of aerospace alloy machining with adaptability and flexibility.

In this study, dissimilar sheets, magnesium alloy AZ91 and aluminum alloy AA6061, were welded using friction stir welding (FSW) with the incorporation of titanium carbide (TiC) reinforcing powders into the weld joints. A novel groove design was presented to restrict nanoparticle segregation during the welding process. Microstructure examination and phase constitution of the interfacial zones showed that the base materials reaction was successfully obtained in the presence of the TiC reinforcing particles. Changes in heat input and stir action had the most significant effect on microstructure evolution, the distribution of nanoparticles, and intermetallic compound formation. Microstructure refinement, the presence of thin intermetallic compounds (IMCs), and homogenous nanoparticle distribution in the stir zone (SZ) were identified as the fundamental factors for the increased mechanical properties of the weld specimens, namely strength, toughness, and hardness profile.

In this study, the microstructure and mechanical characteristics of a super duplex stainless steel (SDSS), S32750 welded by gas tungsten arc welding (GTAW) after post-weld heat treatment (PWHT), were investigated. Microstructure observations after PWHT indicated an increase in the size of austenite laths and globularity due to solution annealing at a high temperature and complete austenite with a few small ferrite islands in the fusion zone (FZ) due to the presence of nitrogen as a strong austenite stabilizer. The phase percentage obtained based on ASTM E562 indicated an almost equivalent ratio for austenite and ferrite after using nitrogen as the shielding gas and PWHT. No evidence of undesired intermetallic phases such as σ, χ, and nitride was detected based on X-ray diffraction (XRD) analysis. According to mechanical characteristics, tensile strength increases after the usage of nitrogen gas, while the elongation of samples increases after PWHT.

This chapter provides an overview of laser welding of lightweight aerospace alloys. First, the types, functions, and principles of laser welding are discussed. Moreover, the key benefits and drawbacks of laser welding techniques compared with conventional welding techniques are thoroughly discussed. Then, lightweight alloys, aluminum and titanium alloys, in laser welding are investigated. In addition to discussing joints of similar materials, this chapter also investigates laser welding joints involving dissimilar materials. The microstructural and mechanical characteristics of laser-welded lightweight alloys used in the aerospace sector are highlighted.

Direct metal laser sintering (DMLS) is a rapid manufacturing technique that has gained a significant attention in recent years due to its ability to produce complex metal parts directly from three-dimensional (3D) digital models. In the field of aeroengine manufacturing, DMLS has the potential to revolutionize traditional manufacturing methods by enabling the production of lightweight, high-strength components with improved performance and reduced production costs. This study provides an in-depth overview of the DMLS process and its applications in aeroengine manufacturing, including the materials considerations required for successful part production. The chapter also highlights the latest advances in DMLS technology and discusses the challenges and opportunities associated with its widespread adoption in the aerospace industry. Overall, this study serves as a comprehensive resource for engineers and researchers interested in DMLS process for aeroengine components.