Microstructure and mechanical properties of in-situ Al13Fe4/Al composites prepared by mechanical alloying and spark plasma sintering

Bulk dense composites of Al-Fe alloys containing 2.5-10 at% Fe were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Supersaturated Al(Fe) solid solutions were obtained by MA for 80 h. The sintered samples are composed of nano and ultrafine needle-like Al13Fe4 phase and angular-shaped Al13Fe4 phase with a size range of 1-2 μm uniformly distributed in the Al matrix. Needle-like Al13Fe4 phase originates from the precipitation of supersaturated Al(Fe) solid solutions, and angular-shaped Al13Fe4 phase originates from the reaction of undissolved Fe particles and the Al melt. The hardness of the alloys varied from 1.44 to 1.97 GPa and Al-10%Fe exhibited highest specific yield strength of 391.1 kN m/kg. The yield strength varied from 657 to 1130 MPa, depending on the Fe content. Excellent plastic strain (>14.5%) were achieved in the alloys containing 2.5-5%Fe, but the Al-10%Fe exhibited elastic behavior only, failing without any macroscopic yielding or plastic strain. The lack of plastic performance of Al-10%Fe is attributed to large amount of undissolved Fe particles reacted with the Al melt to form angular-shaped Al13Fe4, leading to the absence of soft α-Al phase.