Synergistic enhancement of ultra-high thermal conductivity and strength in a high-pressure die-cast Al–Fe–Ni alloy via α-Al purification and bio-inspired eutectic refinement

In this paper, we propose a microstructure optimization strategy involving matrix purification via element B, and refinement of eutectic cells by forming a bio-inspired core-shell structure via element Yb to achieve synergistic improvement in both thermal conductivity and strength of a high-pressure die-cast Al-1.5Fe-1Ni alloy. The die-cast Al-1.5Fe-1Ni-0.15Yb-0.03B alloy exhibits an ultra-high thermal conductivity exceeding 200 W·m -1 ·K -1 along with a yield strength of nearly 90 MPa. In the die-cast alloy, element B purifies the Al matrix by reacting with transition metal impurities to form (Al,M)B 2 borides (M=V, Cr, Mn, Zr, Ti), thereby reducing solute scattering and enhancing thermal conductivity. The fine borides also contribute to the precipitation strengthening. Meanwhile, element Yb promotes the precipitation of Al 3 Yb phases containing Si impurities which are purified from the Al matrix, and forms a bio-inspired core-shell structure around the Al 9 NiFe eutectics to refine the eutectic cells. The refinement and purification effects of Yb improve both thermal conductivity and strength of the die-cast alloy. This work offers a strategic reference for developing high-pressure die-cast aluminum alloys with ultra-high thermal conductivity.