Normal ve Kriyojenik Şartlarda Öğütmenin Aktive Edilmiş Sinterleme Süreçleri ile Geliştirilen Tungsten Esaslı Kompozitlerin Mikroyapı ve Özellikleri Üzerindeki Etkisi

Abstract

Tungsten matrix composites reinforced with TiB2 and Y2O3 particles were fabricated by milling under ambient/cryogenic conditions and Ni activated sintering. Powder blends constituting the W-1 wt. % Ni-2 wt. % TiB2-1 wt. % Y2O3 composition were mechanically milled for 12 h under ambient condition or cryomilled for 10 min or sequentially milled under ambient and cryogenic conditions. Milling was carried out in a high-energy ball mill under ambient condition whereas cryogenic milling was conducted in externally circulated liquid nitrogen. Milled powders were compacted using a hydraulic press and the pellets were sintered at 1400°C for 1 h under Ar / H2 gas flowing conditions. The effects of different milling types on the microstructural and mechanical properties of the sintered composites were investigated. After sintering, in addition to dominant W phase, small amounts of WB and NiW phases were detected in all sintered samples. The application of cryomilling after milling at ambient condition provided the disappearance of the clustered TiB2 and Y2O3 particles in the sintered sample: They were located at the grain boundaries of W1Ni matrix and homogeneously distributed through the microstructure. Sequentially milled and sintered composite had the highest relative density (95.77 %) and the highest microhardness (7.23 GPa) values among the samples. Nanoindentation tests showed that there was an improvement in the hardness and elastic modulus of W matrix phase, which yielded the values of 8.9 and 373.7 GPa, respectively.