International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 09 | Sep 2024
p-ISSN: 2395-0072
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A Technical Review on Deep Cryogenic Treatment of Aluminum Alloys: Microstructural and Performance Enhancements Birendra Singh Karki1, Dr. Anadi Misra2 1Ph.D. scholar (GBPUAT, Pantnagar) Uttrakhand 2Professor (GBPUAT, Pantnagar) Uttrakhand
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Abstract - Aluminum alloys are essential in industries like
strengthening the steel alloy (8). Nevertheless, the latest works emphasize the benefits achieved in the non-ferrous metal, such as in aluminum alloys. Aluminum alloys are used extensively in structural applications for aerospace, defense, and many other purposes due to their specific strengths, stiffer rigidity, toughness, low corrosion, and low cost. For instance, Al alloys 2024 and 7050 are of particular interest for aerospace applications (10). Alloy 2519 is used to create armor for combat vehicles, while rocket parts for Falcon 9 are created using alloy 2198. Demand for betterment is increasing owing to higher mechanical performance required in aerospace applications and other fields.
aerospace, automotive, and manufacturing due to their lightweight and excellent performance. With the growing demand for enhanced properties in these alloys, choosing effective treatment methods has become crucial. Deep cryogenic treatment (DCT) offers a green, low-cost, and efficient solution to improve the microstructure and performance of aluminum alloys without altering their dimensions. This review explores how DCT influences the structural and performance evolution of these alloys. When parameters are carefully optimized, DCT can refine grain structures, increase dislocation density, and optimize secondary phase distribution, resulting in improved mechanical properties, reduced residual stress, enhanced corrosion and wear resistance, and better electrical conductivity. By summarizing key research findings, this paper also provides recommendations for future studies on DCTtreated aluminum alloys.
DCT provides several advantages to aluminum alloys in terms of residual stress removal and improvement in dimensional stability without degrading their mechanical properties (13). Some aluminum alloys, such as 2219 and 3102, are used to function at ultra-low temperatures. Therefore, the microstructure of these aluminum alloys should be strengthened at ultra-low temperatures (14). Research on DCT applied to aluminum alloys is highly undertaken in this direction. This review will summarize the DCT influence on the microstructure of aluminum alloys as well as performance improvements obtained through such processing and discuss insights and perspectives for further material post-treatment development..
Key Words: Aluminum alloys, Aerospace industry, Lightweight, Green technology, Structural evolution, Grain refinement, Dislocation density
1. INTRODUCTION Cryogenic treatment modifies the microstructure of metallic materials at ultra-low temperatures to elevate property levels. Two types are seen: DCT and SCT (1). DCT is the most widely studied form, usually an auxiliary process to conventional heat treatments. It is attractive because of its low cost, simple energy efficiency, and friendliness toward the environment (2). DCT is widely used in the aerospace, automobile, and manufacturing industries. It usually operates within a temperature range of 143K and 77K (3). It commonly uses liquid nitrogen as a refrigerant, due to its safety, availability, and relatively economic factor (4). The process occurs in three stages: cooling, holding, and warming (5). In some processes, DCT is used along with the conventional heat treatment to enhance performance. Among the critical process parameters influencing the efficiency of the process are the soaking temperature, holding time, cooling/warming rates, and the treatment sequence (6).
2. MICROSTRUCTURAL EVOLUTION Recent research shows that deep cryogenic treatment (DCT) can significantly enhance the overall performance of aluminum alloys, primarily by altering their microstructures. The key microstructural elements affected by DCT include grains, dislocations, and secondary phases. 2.1. Effect of DCT on Grain Size The effects of DCT on grain size are closely related to the structure of dislocations that develops during the treatment. First, the dynamic recovery of dislocations suppressed, therefore the growth of dislocation density; thus, the DCT causes grain refinement. For instance, Li et al.(17) indicated that the mean grain size of 2024-T351 aluminum alloy reduced from 33.46 µm through RT-LP to 28.30 µm after CLP at -130 ± 2°C. Later on, they found that, in a separate experiment, the grain size was 28.20 µm after CLP but it further reduced to 27.13 µm as DCT for 4 hours before CLP was used (CLP-4) (28).
The significant part of work established was on the DCT's effects on ferrous metals, focusing on transforming austenite to martensite (7) and secondary carbides precipitation for
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