02.05.2009
L. Veleva, Z. Oksiuta, U. Vogt, N. Baluc
Abstract:
W–(0.3–2)Y2O3 and W–(0.3–2)Y materials (in wt.%) have been manufactured by conventional powder metallurgy methods including dry mechanical alloying of elemental powders in Ar atmosphere, cold pressing in air using a pressure in the range of 150–250MPa and sintering at 1800 ◦C either in vacuum or in Ar atmosphere. The mechanical alloying time was optimized by means of X-ray diffractometry and scanning electron microscopy analyses of the particles. It was found that it should not exceed 15 h, in order to obtain small and homogeneous particle sizes and crystallite sizes and to avoid formation ofWC impurities. The density of the sintered specimens was found to increase with Y2O3 and Y contents. The highest density of about 90% was obtained for the W–2Y material, while the highest microhardness of 1790HV0.2 was measured for theW–2Y2O3 material. Scanning electron microscopy observations revealed that sintering occurred, at least partially, from liquid phase, the amount of the corresponding dense regions increasing with the Y2O3 or Y content.
