Dynamic and static strain aging in AlFeCrX alloys processed by laser powder bed fusion

Abstract

In this study, newly designed high-strength AlFeCrX (X = Si, Ti, and TiSi) alloys were fabricated using laser powder bed fusion (LPBF). The mechanical properties and strain rate sensitivity (m) of as-built AlFeCrX alloys were evaluated through uniaxial compression tests using strain rate change (SRC) across various temperatures (RT–400 °C) and strain rates (10–2–10–5 s−1). For comparison, a LPBF-processed AlSi10Mg commercial alloy was also tested. Transmission electron microscopy (TEM) analysis confirmed the formation of a supersaturated solid solution of transition elements in the α-Al matrix of the as-built LPBF AlFeCrX alloys, particularly Ti, Si, and Cr, while Fe was primarily observed precipitating along grain boundaries. The stress–strain curves of the LPBF AlFeCrX specimens, which clearly show strain rate variations, exhibited no serrated flow but revealed negative m values at testing temperatures ranging from 150 to 200 °C. This behavior is attributed to solute–dislocation interactions, which drive dynamic and static strain aging (DSA and SSA) mechanisms. Consequently, solutes play a crucial role in the material intermediate-to-high-temperature response, because of the diffusivity and supersaturation of transition element solutes in the as-built AlFeCrX alloys.