Multi‐Objective Optimisation of Surface Integrity and Energy Consumption in Ultrasonic‐Assisted Roller Burnishing of Al‐6082‐T6 Alloy Under MWCNT‐NMQL

ABSTRACT Al‐6082‐T6 alloy is widely used in aerospace, automotive and defence industries due to its excellent durability, formability, corrosion resistance and high thermal conductivity. However, achieving high surface quality with sustainable manufacturing remains challenging. Roller burnishing, a chipless surface‐finishing process, improves surface quality and mechanical properties through plastic deformation. In this study, conventional and ultrasonic vibration–assisted roller burnishing of Al‐6082‐T6 alloy under four burnishing conditions, such as dry, Ranque–Hilsch vortex tube (RHVT) cold air, minimum quantity lubrication (MQL) and multi‐walled carbon nanotube–enhanced MQL (MWCNT‐MQL), are investigated. The experiments were conducted at a constant burnishing speed and feed, and variable burnishing depths. The burnishing force, energy consumption, surface roughness, microhardness and microstructure were measured under ultrasonic vibration and nanofluid lubrication conditions. The surface roughness decreased gradually from dry to RHVT, MQL and nanofluid MQL (NMQL) conditions for both conventional and ultrasonic‐assisted burnishing. The burnishing depth was increased to improve plastic deformation, surface hardening and surface finish; however, the burnishing force and energy consumption increased. Ultrasonic vibration aided material flow and reduced deformation resistance. NMQL provided superior lubrication and cooling, which resulted in lower burnishing forces and energy requirements. Microstructural observations revealed deeper deformation zones under ultrasonically assisted NMQL conditions. Finally, NSGA‐II TOPSIS optimisation identified ultrasonic‐assisted NMQL as the optimal condition, providing the best compromise among burnishing responses.