47. sam2x5: stronger than the strongest steel
Name: Arash Yazdani
Grad Year: 2020
SAM25 is an amorphous steel with a chemical composition of Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. In this study, dense samples of this alloy were prepared using the spark plasma sintering technique in a graphite die, at varying temperatures ranging from 615 to 675oC, under nitrogen atmosphere, a heating rate of 500oC/min, and a pressure of 100 MPa without any hold time at the sintering temperature. X-ray diffraction results showed that increasing the SPS temperature resulted in the devitrification of mainly-carbide-based phases from the amorphous matrix ending up with formation of composite specimens whose crystallinity spans from 12 wt.% to 78 wt.%. Density of samples sintered above 650°C exceeds the theoretical density of the amorphous alloy, showing that the densification was achieved accompanied by the formation of crystalline phases with a higher density. Results of microhardness tests showed that there is an incremental trend between the hardness and sintering temperature which could be most probably due to the (i) enhancement of relative density, (ii) the formation of hard ceramic phases with strong covalent bonds, and (iii) the formation of reinforcing ceramic particles in the matrix. Split Hopkinson Pressure Bar tests were carried out to measure the mechanical response of the sintered specimens under dynamic deformation, showing a yield strength of 2200 MPa under strain rate of 900 s-1.
Industry Application Area(s)
Aerospace, Defense, Security | Materials