ADVANCED MATERIALS & PROCESSES | MARCH 2024 21 Repair Technology, Aerospace Applications, Composition-Microstructure- Properties, Thermomechanical Processing, Biomedical and Health Care Applications, Environmental Applications, Extraction, Forming, Machining and Joining, Metal Matrix Composites and Intermetallics, Marine, Offshore, and Automotive Applications, Materials 4.0, Near Net Shape, and Powder Consolidation. The conference highlighted significant changes since the 14th World Conference in Nantes, France, in 2019. A surge in titanium demand in late 2019 and early 2020, driven by orders for fuel-efficient aircraft, was followed by a sharp decline in global air traffic and titanium needs because of the COVID-19 pandemic. The pandemic also resulted in the idling of major titanium facilities in the U.S., leading to a reliance on imported titanium sponge, primarily from Japan. As pandemic restrictions eased, the demand for titanium gradually increased, with expectations of reaching pre-pandemic consumption levels by 2025. The titanium industry is experiencing a significant expansion in melt and forge capacity to meet this growing demand. In the U.S., ATI has commissioned a new electron beam cold hearth and vacuum arc remelt (EBCHM-VAR) furnace, increasing melt capacity by 60%, and reopened triple VAR operations in Albany, Oregon. Perryman Co. is adding an EBCHM, two VAR furnaces, and a 4500-ton forging press to increase annual melt capacity to 42 million pounds by Q4 2024. Precision Castparts Corp., TIMET’s parent company, is investing $500M in a Ravenswood, West Virginia, melt facility with a focus on 100% clean, renewable energy, set to commence operations in 2025[1,2]. NEW ALLOY DEVELOPMENT New titanium alloys are being developed to meet the challenges of next-generation airframe, aerospace propulsion, medical, and industrial application requirements. ATI has introduced patented alloys, including TITAN 23, TITAN 27, and TITAN 171. TITAN 23 is a near-beta alloy with customizable strength and ductility, suitable for additive manufacturing. TITAN 27 is an alpha-beta alloy with strengths comparable to Ti-6Al-4V but with higher elongation, and TITAN 171 is a high-strength near-beta alloy designed for improved elevated temperature performance. A collaborative partnership between GE Aerospace and TIMET led to the development of Ti-725, which is based around Ti-6Al-4V with small additions of Fe, Mo, and Si leading to increased hardenability and higher tensile and fatigue strength in thick sections. TIMET has also introduced the TIMETAL 4XX series, including Ti-407, with moderate strength, increased ductility, and improved Charpy Impact energy absorption, and Ti-412, with 15-20% higher strength than Ti-407. TIMETAL 542 (Ti-542) is an alpha-beta alloy offering higher strength than Ti-6Al-4V, achieved with minimal alloy additions. TIMETAL 575 (Ti-575) is a high-strength alpha-beta titanium alloy with superior fatigue properties compared to Ti-6Al-4V, designed for aerospace engine and structural applications. ADDITIVE MANUFACTURING Over the past decade, additive manufacturing (AM) has undergone significant evolution, with notable shifts in research focus. Initially, electron beam powder bed fusion (EBPBF) processes garnered substantial attention, but in recent years, the U.S. has witnessed a surge in the adoption of laser powder bed fusion (LPBF). Ti-6Al-4V remains a prevalent choice, but exploration and optimization of process parameters for other alloys such as Ti-6Al-2Sn-4Zr-2Mo, titanium aluminides, Ti-185, and commercially pure titanium (CP Ti) is underway. A groundbreaking post-processing approach, leveraging low-temperature, high-pressure hot isostatic pressing (LTHP-HIP), has exhibited promising results in enhancing fatigue performance and minimizing scatter. This technique, championed by Boeing, involves lower temperatures to mitigate alpha lath coarsening kinetics, preserving strength, and minimizing free slip distances. Despite a slight debit in fatigue crack growth rate, the overall benefits in fatigue outweigh the minor impact on damage tolerance. Boeing is advocating for Aerospace Materials Specification (AMS) 7028 for LPBF Ti-6Al-4V post-processed using this method as a potential industry standard, aiming to reduce costs. The U.S. Navy has incorporated AM, with over 500 approved parts on multiple ships and submarines, releasing guidelines for the qualification of components produced through powder bed fusion and directed energy deposition (DED). In addition, the Federal Aviation Administration has issued Advisory Circular (AC) 33.15-3, offering guidance for powder bed fusion additive manufacturing of aircraft engine parts. The casting industry, grappling with a skilled labor shortage exacerbated by the pandemic, is turning to AM as an alternative for producing structural components, addressing prolonged lead times for casting procurement. This shift has led to a focus on large- Co-author Vasisht Venkatesh stands in front of the Edinburgh International Conference Centre, Scotland.
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