Strain engineering: A sustainable alternative to avoid using strategic and critical raw materials in developing high-performance alloys

The quest to develop high-performance metallic alloys with properties superior to traditional alloys has driven scientists to synthesize numerous chemical alloy compositions over the past few decades. However, many of these compositions heavily depend on strategic and critical raw materials (S&CRMs), leading to significant environmental impacts due to intensive mining practices. Through this work, we present a scientific rationale to highlight that high performance in metal alloys can be achieved through strain engineering approach, which is a sustainable alternative to reduce the use of S&CRMs. Strain engineering refers to the process of deforming materials to induce changes in their microstructure, such as increasing dislocation density, promoting twinning, forming ultra-fine grained (UFG) or nano-crystalline (NC) structures, and in some cases, triggering phase transformations like transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) to enhance its properties. This encompasses conventional thermo-mechanical processing (TMP) methods, including rolling, forging, extrusion, and drawing, as well as advanced techniques commonly referred to as severe plastic deformation (SPD), such as High-Pressure Torsion (HPT), Equal Channel Angular Pressing (ECAP), Friction Stir Processing (FSP), and Twist Extrusion (TE). Through a comprehensive data-driven analysis of pure elements and multi-principal element alloys (MPEAs), also known as high-entropy alloys (HEAs), we demonstrate that precise strain engineering techniques on alloys without S&CRMs can achieve mechanical properties well comparable to the S&CRMs based traditional alloys, suggesting a strong need of further research in this direction to eliminate the excessive reliance on S&CRMs. Furthermore, strain-engineered materials not only exhibit enhanced resistance to fatigue, corrosion, and wear but also offer significant weight saving. Even thinner strain-engineered materials outperform thicker traditional alloys in terms of performance. This study serves as a catalyst to revive interest in strain engineering and explore the ultimate potential of materials traditionally considered mechanically weak.