Co-design of grain heterogeneity and precipitate hierarchy for strength-ductility-conductivity synergy in a conductive Cu alloy

Abstract

In this work, a coupled multiscale microstructural design strategy was developed for a Cu-5Ni-0.7Si-0.4Al alloy by integrating partial recrystallization-induced grain heterogeneity with hierarchical precipitation. Partial recrystallization produced heterogeneous grains spanning the micrometer to submicrometer scale, while Ni-Si–Al alloying promoted a site-dependent precipitate hierarchy, including intergranular δ-Ni2Si, intragranular δ-Ni2Si, and nanosized Ni-Al-enriched precipitates consistent with an L12-ordered structure. The resulting architecture is inferred to regulate dislocation motion and improve strain compatibility during deformation. The optimized alloy achieves a yield strength of 800 MPa, an ultimate tensile strength of 840 MPa, an elongation of 15%, and an electrical conductivity of 38% IACS. GRAPHICAL ABSTRACTThree micrographs and one scatter plot show heterogeneous grains, multi scale precipitates, and conductivity versus strength trends.The figure shows four visuals related to microstructure and mechanical performance. The first visual is a transmission electron micrograph labeled with a scale bar of 200 nanometers. Large irregular grain regions are outlined by dashed contours and several areas are marked with text pointing to delta hyphen nickel silicon. The second visual is another transmission electron micrograph with a 200 nanometer scale bar, showing finer grains and multiple bright and dark regions with arrows pointing to features also labeled delta hyphen nickel silicon. The third visual is a higher magnification transmission electron micrograph with a 20 nanometer scale bar, containing several rounded darker spots. Arrows highlight these spots and text labels them as L one two. Above the three micrographs, an arrow runs from left to right with text indicating greater than 120 nanometers, approximately 40 nanometers, and less than 8 nanometers. Below the micrographs, the words heterogeneous grains appear under the first area and multi scale precipitates under the second area. The fourth visual is a schematic illustration at the lower left showing stacked layers with polygonal grains; some grain interiors and boundaries contain small red and green dots representing precipitates of different sizes. At the lower right, a scatter plot shows electric conductivity in percent of international annealed copper standard on the horizontal axis from 25 to 50 with ticks every 5 units, and tensile strength multiplied by elongation in megapascal percent on the vertical axis from 2000 to 16000 with ticks every 2000 units. Numerous symbol types represent different copper nickel silicon based alloys listed in a legend, including copper nickel silicon, copper nickel silicon tin, copper nickel silicon titanium, copper nickel silicon magnesium, copper nickel silicon cobalt, copper nickel silicon calcium zirconium, copper nickel silicon scandium, copper nickel silicon chromium, copper nickel silicon molybdenum, copper nickel silicon cobalt molybdenum, copper nickel silicon cobalt tungsten, copper nickel silicon cerium, copper nickel silicon zirconium hafnium, and this work. Data points are scattered across the plot with several marked by large star symbols along an upward trending distribution. All data are approximate.