Comparative Analysis of Mechanical Properties in Additive vs. Subtractive Manufacturing Metals

Thesis Abstract

Advancements in manufacturing technology have significantly transformed the production of metallic components, with additive manufacturing (AM) and subtractive manufacturing (SM) emerging as dominant modalities, each offering distinct advantages and limitations. Despite their widespread adoption, existing literature reveals a paucity of comprehensive comparative analyses focusing on the mechanical properties of metals fabricated through these methods, which is critical for optimizing application-specific performance and ensuring structural integrity. This study aims to systematically compare the mechanical properties—specifically tensile strength, hardness, fracture toughness, and fatigue life—of metals produced via additive and subtractive manufacturing processes. The primary objectives are to identify significant differences in these properties, elucidate the influence of process parameters on mechanical performance, and provide insights into the microstructural characteristics contributing to observed variations. The research adopts a quantitative, cross-sectional design, grounded in a positivist paradigm, to facilitate objective comparison. The study population comprises commercially available aluminum alloys (specifically Al 6061) and titanium alloys (Ti-6Al-4V), selected based on their prevalent use in critical engineering applications. A stratified random sampling technique is employed to select a total sample of 120 specimens, with 60 manufactured via directed energy deposition (DED) additive methods and 60 produced through CNC-based subtractive methods. Data collection involves the use of standardized testing instruments, including a universal testing machine for tensile properties, Vickers hardness tester, compact tension test setup for fracture toughness, and a servo-hydraulic fatigue testing system for fatigue life analysis. Validity and reliability of the measurement instruments are ensured through calibration and adherence to ASTM standards. Data analysis comprises descriptive statistics to summarize the data, followed by Analysis of Variance (ANOVA) to determine significant differences in mechanical properties between manufacturing methods, and regression analysis to explore the relationship between process parameters and material performance. Microstructural investigations are conducted via optical and scanning electron microscopy, with energy-dispersive X-ray spectroscopy (EDX) complementing to elucidate phase composition and defect distribution. The theoretical framework integrates the Dislocation Theory of Plasticity to interpret mechanical behavior, and the Process-Structure-Property model to link manufacturing methods with microstructural features and resultant properties. It is anticipated that the results will reveal statistically significant differences, with additively manufactured metals exhibiting anisotropic microstructures, higher porosity, and variable mechanical properties compared to their subtractively machined counterparts. Specifically, additive specimens are expected to display superior tensile strength and fatigue resistance owing to refined microstructural features, whereas subtractive components may demonstrate higher hardness due to machining-induced surface effects. Findings will contribute novel insights into the microstructure-property relationships underpinning different manufacturing processes and identify key process parameters influencing mechanical performance. This study extends current knowledge by providing a robust, empirical comparison of metallic materials produced through AM and SM, thus informing manufacturing decision-making and quality control in industries such as aerospace, automotive, and biomedical engineering. The primary conclusion underscores the importance of process optimization tailored to desired mechanical characteristics. Recommendations include adopting hybrid manufacturing strategies to leverage advantages of both methods and further integrating non-destructive evaluation techniques for real-time quality assurance. Future research should explore the long-term durability and corrosion resistance of these materials under operational conditions to complement the mechanical insights gained.