Optimizing high-pressure sliding process parameters for grain refinement and enhanced mechanical properties using response surface methodology approach

Abstract

Lightweight technology has emerged as a crucial focus within transportation machinery manufacturing, driving the pursuit for materials with exceptional strength-to-weight ratios. To address this need, ultra-fine grain (< 500 nm) and nanostructured (< 100 nm) materials are being developed using severe plastic deformation (SPD) techniques, particularly in confined flat sheets. This study focuses on the Multi Pass Incremental Feed High-Pressure Sliding (MPIF-HPS) technique, which offers significant potential for industries such as aerospace and automotive by enhancing the mechanical properties of materials like AA 7075 alloy. This work investigates the development and characterization of ultrafine-grained materials through SPD, focusing on the correlation between ultrafine grain structures and their distinct properties. Utilizing MPIF-HPS processes and design of experiment (DoE) methodologies, the study evaluates the evolution of fine-grained microstructures and the enhancement of boundary characteristics with increasing strain in AA 7075 alloy. The grain size was refined from 600 µm to 6 µm, indicating significant microstructural improvement. Concurrently, mechanical properties were notably enhanced, with hardness increasing from 102 to 165 HV, yield strength from 250 to 605 MPa, and ultimate tensile strength (UTS) from 400 to 650 MPa. The study systematically optimized processing parameters, including pressure, sliding distance, and number of passes, to determine the ideal conditions for grain refinement and mechanical performance. These findings underscore the critical role of strain-induced boundary characteristics in determining the material's final properties, paving the way for tailored solutions to meet specific industrial requirements.