Shock Wave Response of Iron-Based Metallic Glass Matrix Composites

Abstract

The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of the presence of partial crystallinity on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe_49.7Cr_17.7Mn_1.9Mo_7.4W_1.6B_15.2C_3.8Si_2.4. The samples, designated SAM2X5-630 and SAM2X5- 600, are partially crystalline and X-ray amorphous, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be about 12.5 GPa for SAM2X5-630 and 8 GPa for SAM2X5-600. The former HEL result is higher than elastic limits for any BMG reported in the literature thus far. Both SAM2X5-630 and SAM2X5-600 undergo strain-softening beyond the HEL but seem to recover post-yield strength at a certain higher threshold peak stress. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding.