Metastable alloy bulk bodies in the Fe–W system prepared by mechanical alloying and shock compression

Abstract

Bulk bodies of metastable alloys including supersaturated solid solutions and amorphous phases in the iron (Fe)–tungsten (W) system were prepared by mechanical alloying (MA) and shock compression. The X-ray diffraction patterns of the W solid solutions were obtained for the MA-treated powders in the FexW100−x system with Fe content of x≤30 mol%, and that of Fe solid solution was obtained with an Fe content of x=90 mol%. For the mixed powders with Fe content of 40≤x≤70 mol%, the peaks of Fe completely disappeared, and the amorphous halo-like patterns were observed around the (110) peak of W solid solution. For the mixed powder with an Fe content of 80 mol%, an X-ray diffraction pattern of a two-phase mixture of Fe and W solid solutions was obtained. For the MA-treated powders, the lattice parameters of W solid solutions were smaller than that of pure W, and those of Fe solid solutions were larger than that of pure Fe. 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 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 without decomposition or recrystallization. Above a driving shock pressure of 40.1 GPa in capsule for the 30:70 mol% Fe–W system and that of 30.5 GPa for the 50:50 mol% Fe–W system, the X-ray diffraction patterns of the recovered bulk bodies showed the appearance of the peaks of Fe7W6 intermetallic compound and the peaks of Fe. The recovered specimens of the metastable solid solution phases in the 80:20 mol% Fe–W system did not recrystallize or decompose up to a driving shock pressure of 39.5 GPa. It was confirmed by the Electron Probe Micro Analysis (EPMA) that Fe and W 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 pure W polycrystals.