Compositionally graded aluminum-silicon alloy fabricated via friction extrusion

Abstract

A novel solid-phase gradient alloying technique was developed for a high throughput composition-microstructure-mechanical property assessment. Friction extrusion of a two-piece billet setup facilitated the formation of a seamless compositionally graded aluminum (Al)-silicon (Si) extrudate rod, with Si concentration in Al matrix gradually increasing from ~1 at. % at one end to ~7 at. % at the other end of the rod. We observed a strong dependence of the Al grain size, morphology, and texture on the Si concentration. The Si particles pinned the recrystallized grain boundaries resulting in refined (< 10 um) and textured grains in the high Si content region, while the Al grains in the low Si region are equiaxed, randomly textured, and with a larger average size (~50 um). The hardness of Al-Si gradient extrudate increases by ~50% percent with a 6 at.% increase in Si content due to Hall Petch and particle strengthening effects. Our approach demonstrates the use of a solid phase processing technique to successfully produce a defect-free continuously compositionally graded bulk components thus overcoming the limitations of porosity and material heterogeneities commonly observed in other techniques such as by additive laser deposition. • A novel solid-phase gradient alloying technique is developed. • Current method provides a microstructure applicable to structural applications. • Effect of Si content on microstructure and performance of Al-Si alloy is displayed.