Application of SPS consolidation and its influence on the properties of the FeAl20Si20 alloys prepared by mechanical alloying

The FeAl20Si20 alloy was prepared by a combination of short-term mechanical alloying and spark plasma sintering. The processing parameters either of the mechanical alloying or spark plasma sintering were optimized to yield the maximal mechanical properties of the alloy. For the mechanical alloying, two amounts of powders batch (5 g or 20 g) were compared. The spark plasma sintering regimes combined pre-pressing prior heating and vice versa, direct and pulse current flow. The MA + SPS alloys exhibited ultrafine-grained microstructure composed of FeSi, Fe3Si and Fe3Al2Si3 phases (with an average crystallite size of approximately 30 nm) with a presence of randomly distributed Al2O3 particles (with diameters ranging from 5 to 100 nm). The FeSi, Fe3Si phases were supersaturated by Al, which resulted in an increase of lattice parameters. The hardness of the compact alloys reached up to approximately 1100 HV 0.1 for both the powder batches. The 20 g samples showed a standard deviation nearly half the of 5 g powder batches and the 20 g prepared by a regime combining pre-pressing prior heating up to consolidation temperature using pulse current flow resulted in the highest compressive strength of 2008 MPa. Combination of pre-pressing prior heating-up also reduced the increase of the Fe3Al2Si3 phase weight fraction especially in the 5 g alloys that otherwise had a tendency to microstructural coarsening.