Microstructural Evolution and Property Enhancement through Large Strain Extrusion Machining: A Review

Large Strain Extrusion Machining (LSEM) is a developing hybrid manufacturing technique that integrates conventional machining with severe plastic deformation to induce ultrafine or nanostructured grain formation through dynamic recrystallisation and grain breakdown. By imposing high plastic strain during chip formation, LSEM significantly enhances material properties, including hardness, strength, wear resistance, and fatigue life, highly sought after in aerospace, biomedical, and automotive applications. The process offers precise control over microstructure by tuning machining parameters such as cutting speed, feed rate, tool geometry, and chip compression ratio, enabling the customisation of material properties to meet specific functional requirements. Furthermore, the continuous chip formation in LSEM facilitates the scalable production of bulk nanostructured materials from a wide range of metallic materials. Despite its potential, challenges persist in understanding the underlying mechanisms governing microstructural evolution and in optimizing process parameters across different alloys. Advancements in tool design, in-situ monitoring, and predictive modelling are also critical for broader industrial adoption. The present paper critically reviews the current state of knowledge on the microstructural, mechanical, and tribological aspects of LSEM, identifies key research gaps, and outlines directions for future development to fully harness its potential as a transformative manufacturing process.