Metastable BCC and FCC alloy bulk bodies in Fe-Cu system prepared by mechanical alloying and shock compression

Bulk bodies of metastable body-centered-cubic (BCC) and face-centered-cubic (FCC) alloys of solid solutions in the iron (Fe)-copper (Cu) system were prepared by mechanical alloying (MA) and shock compression. The X-ray diffraction pattern of the BCC structure was obtained for the MA-treated powder in the Fe-Cu system with a Cu content of less than about 30 mol%, and those of FCC structure were obtained for the MA-treated powders in Fe-Cu systems with a Cu content of larger than about 30 mol%. The lattice parameters of both the BCC and FCC structures of the MA-treated powders were larger than those of pure Fe and pure Cu, respectively. No large crack could be observed in shock-consolidated bulk bodies, and the cross sections of the bulk bodies showed a metallic gloss. The X-ray diffraction patterns of both types of shock-consolidated bulk bodies formed in a specific low pressure range did not change significantly from those of the MA-treated powders, which indicated that the metastable phases were successfully consolidated by shock compression. Above a driving shock pressure of 13.0 GPa in brass capsule, the recovered specimens of the BCC structure in the Fe-Cu system (Fe:Cu=80:20 in mol%) began to decompose to Fe and Cu, while the recovered specimens of the FCC structure in the Fe-Cu system (Fe:Cu=50:50 in mol%) did not decompose up to a driving shock pressure of 14.9 GPa. It was confirmed by Electron Probe Micro Analysis (EPMA) that Fe and Cu dispersed well at the submicron level in the shock-consolidated bulk bodies. The Vickers hardnesses of the bulk bodies were much higher than those of pure Fe and Cu polycrystals.