Multi-objective optimization of milling Ti-6Al-4V alloy for improved surface integrity and sustainability performance

Cica, Djordje (author), Tešić, Saša (author), Markovic, Milisav (author), Sredanović, Branislav (author), Borojević, Stevo (author), Zeljković, Milan (author), Kramar, Davorin (author), Pušavec, Franci (author)

Ti-6Al-4V is a titanium-based alloy that is widely used in a diverse range of applications, especially in industries such as biomedical and aerospace. Several lubricooling techniques have been introduced to enhance the machinability of these materials. Among them, environmentally friendly strategies are gaining in importance, with sustainability trends rising in manufacturing. The present research investigates the effect of two eco-friendly lubricooling techniques (minimum quantity lubrication and cryogenic cooling), along with other cutting parameters (cutting speed and feed per tooth), on the surface roughness and microhardness of the machined surfaces, which are identified as one of the most frequently implemented indicators of surface integrity in the ball-end milling of the Ti-6Al-4V alloy. In addition, the total electrical energy consumption of the machine tools under different cooling/lubrication conditions was also analyzed. The results obtained showed that cryogenic cooling enhanced milling performance as compared to MQL. Moreover, a multi-objective parameter optimization model integrating the machining responses (surface roughness, microhardness, energy consumption, and productivity) and sustainability metrics (environmental impact, operator’s health and safety, and waste management) was introduced. It was found that cryogenic cooling outperformed the MQL method in terms of both machining performance and environmental impact. An analysis of variance (ANOVA) was carried out to evaluate the significance of each process parameter on the multiple performance index. The results indicate that feed per tooth, cooling method, and cutting speed were significant, with respective contributions of 39.4%, 36.8%, and 22.9%. Finally, the optimal parameter setting was verified through a confirmation test and results reveal that an improvement was observed in the machining responses and multiple performance index.

• Language: English
• Keywords: MQL, cryogenic, 3D surface roughness, microhardness, energy consumption, sustainability assessment, multi-objective optimization
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 17 str.
• Numbering: Vol. 13, iss. 3, art. 221
• PID: 20.500.12556/RUL-170924
• UDC: 621.7:536.483
• ISSN on article: 2075-1702
• DOI: 10.3390/machines13030221
• COBISS.SI-ID: 243233027
• Publication date in RUL: 21.07.2025

Record is a part of a journal

• Title: Machines
• Shortened title: Machines
• Publisher: MDPI
• ISSN: 2075-1702
• COBISS.SI-ID: 17129750

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• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.