EFFECT OF TITANIUM AND CHROMIUM ON THE MICROSTRUCTURE OF TUNGSTEN-MANGANESE ALLOYS PREPARED BY MECHANICAL ALLOYING

摘要

Alloys of tungsten 20% manganese 17% titanium and tungsten 18% manganese 17% chromium (at%) were prepared by mechanical alloying and sintering from 1225 to 1425°C. The microstructures were examined by XRD and SEM/EDS. In the titanium-containing alloy, XRD patterns revealed peaks related to TiN and MnTi_2O_4. In the chromium-containing alloy, peaks related to a chromium-rich phase and MnCr_2O_4 were observed. SEM backscattered images of the titanium-containing alloys depicted two distinct phases: a tungsten-rich phase and a manganese-titanium oxide. The addition of titanium increased the solubility of manganese in the tungsten-rich phase, compared to tungsten-manganese alloys, to 6.3 at% Mn with 3.9 at% Ti after sintering at 1275°C for 30 min. Alternatively, the addition of chromium produced no significant improvement in the solubility of manganese; however, the solubility measurements were more consistent. Although the microstructural constituents of both alloys underwent grain growth at higher sintering temperatures, the microstructure remained relatively fine.