{"title":"Constitutive modeling and formability insights for AA 2198 during natural aging and its application to stretch forming","authors":"Sook Lee, Taek Jin Jang, Deok Chan Ahn, Jeong Whan Yoon","doi":"10.1007/s12289-025-01917-4","DOIUrl":null,"url":null,"abstract":"<div><p>This study investigates the influence of natural aging on the formability and plastic deformation behavior of AA 2198, a third-generation Al-Li alloy, under W-temper conditions to address its low formability. Mechanical tests, including uniaxial tensile, bulge, and Nakazima tests, were performed to evaluate the evolution of mechanical properties, anisotropy, and formability during natural aging. A phenomenological hardening model was developed and validated through yield surfaces and finite element simulations, incorporating insights from forming limit tests. During natural aging, yield strength and ultimate tensile strength increased, while elongation decreased. Natural aging was completed within 7.6 days, with solute and precipitation strengthening identified as primary mechanisms. Anisotropy appeared during early natural aging but remained stable, attributed to the aluminum crystal structure and rolling-induced crystallographic texture, independent of natural aging effects. The proposed hardening model effectively predicted the evolution of yield strength, anisotropy, and formability across natural aging conditions. The forming limit curve for natural aging at 0.5 h was significantly higher than other conditions, demonstrating enhanced formability through W-temper heat treatment. Finite element simulations and forming tests revealed that natural aging at 0.5 and 6.0 h supported stable forming, with natural aging at 6.0 h offering optimal thickness distribution and safety margins. Beyond 24.0 h of natural aging, formability diminished significantly due to wrinkling and fractures. This study highlights the utility of the hardening model and numerical framework as efficient virtual tools for optimizing the W-temper forming of aerospace components.\n</p></div>","PeriodicalId":591,"journal":{"name":"International Journal of Material Forming","volume":"18 2","pages":""},"PeriodicalIF":2.6000,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Material Forming","FirstCategoryId":"88","ListUrlMain":"https://link.springer.com/article/10.1007/s12289-025-01917-4","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, MANUFACTURING","Score":null,"Total":0}
引用次数: 0
Abstract
This study investigates the influence of natural aging on the formability and plastic deformation behavior of AA 2198, a third-generation Al-Li alloy, under W-temper conditions to address its low formability. Mechanical tests, including uniaxial tensile, bulge, and Nakazima tests, were performed to evaluate the evolution of mechanical properties, anisotropy, and formability during natural aging. A phenomenological hardening model was developed and validated through yield surfaces and finite element simulations, incorporating insights from forming limit tests. During natural aging, yield strength and ultimate tensile strength increased, while elongation decreased. Natural aging was completed within 7.6 days, with solute and precipitation strengthening identified as primary mechanisms. Anisotropy appeared during early natural aging but remained stable, attributed to the aluminum crystal structure and rolling-induced crystallographic texture, independent of natural aging effects. The proposed hardening model effectively predicted the evolution of yield strength, anisotropy, and formability across natural aging conditions. The forming limit curve for natural aging at 0.5 h was significantly higher than other conditions, demonstrating enhanced formability through W-temper heat treatment. Finite element simulations and forming tests revealed that natural aging at 0.5 and 6.0 h supported stable forming, with natural aging at 6.0 h offering optimal thickness distribution and safety margins. Beyond 24.0 h of natural aging, formability diminished significantly due to wrinkling and fractures. This study highlights the utility of the hardening model and numerical framework as efficient virtual tools for optimizing the W-temper forming of aerospace components.
期刊介绍：
The Journal publishes and disseminates original research in the field of material forming. The research should constitute major achievements in the understanding, modeling or simulation of material forming processes. In this respect ‘forming’ implies a deliberate deformation of material.
The journal establishes a platform of communication between engineers and scientists, covering all forming processes, including sheet forming, bulk forming, powder forming, forming in near-melt conditions (injection moulding, thixoforming, film blowing etc.), micro-forming, hydro-forming, thermo-forming, incremental forming etc. Other manufacturing technologies like machining and cutting can be included if the focus of the work is on plastic deformations.
All materials (metals, ceramics, polymers, composites, glass, wood, fibre reinforced materials, materials in food processing, biomaterials, nano-materials, shape memory alloys etc.) and approaches (micro-macro modelling, thermo-mechanical modelling, numerical simulation including new and advanced numerical strategies, experimental analysis, inverse analysis, model identification, optimization, design and control of forming tools and machines, wear and friction, mechanical behavior and formability of materials etc.) are concerned.
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