Papers by Keyword: Blended Elemental Powder

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Authors: Muziwenhlanhla A. Masikane, Hilda K. Chikwanda, Iakovos Sigalas
Abstract: Over the past years, the blended elemental powder metallurgy (PM) approach has been identified as one of the most promising strategies to reduce the cost of titanium-based components. However, oxygen pick-up, inhomogeneity of the microstructure and chemical composition are sometimes reported for PM parts. This work compares properties of a blended elemental Ti-6Al-4V alloy obtained by sintering under argon gas atmosphere with those of a vacuum cast alloy. Argon was purified by passing it through a series of oxygen and moisture traps prior to being introduced into the sintering furnace. Casting was performed under vacuum (1 x 10-3 mbar). The starting material in both processes was the cold isostaticaly pressed blended elemental (BE) Ti-6Al-4V powder compact. The BE powder was prepared by mixing 60Al-40V master alloy powder with commercial Grade 4 titanium powder (0.377 wt.% O2). The sintered and cast alloys were compared on the basis of oxygen pick-up, density, microstructure, chemical composition and hardness to determine which method is better. Although the BE approach could not eliminate the common challenges associated with powder metallurgy processing of Ti alloys, oxygen pick-up and additional contamination was lower compared vacuum casting. Sintering at 1350°C for 1 h could not achieve full density compared to casting, but the microstructure appeared more homogeneous. Both sintered and cast Ti6Al4V alloys were harder than wrought Ti6Al4V due to a high concentration of interstitial oxygen. The sinterered and sintered plus HIPed Ti6Al4V alloys were softer than as-cast Ti6Al4V due to lower oxygen pick-up and incomplete densification. From the contamination and homogeneity perspective, the BE approach is an attractive technique for processing of Ti6Al4V alloy.
Authors: Stiliana Raynova, M. Ashraf Imam, Hunter Taylor, Fei Yang, Leandro Bolzoni
Abstract: Microwave sintering (MWS) was used to consolidate hydride de-hydride Ti powder and blended elemental Ti6Al4V, Ti5Fe and Ti5Al5Mo5V3Cr (Ti5553) powder mixtures. The amount of powders used to prepare the powder compacts was scaled up to 500g.The effect of the MWS conditions on the relative density, porosity distribution, microstructure and tensile properties were studied. Furthermore, uniformity in distribution of the alloying elements was checked. For most of the materials considered, a combinations of sintering temperature of 1200oC and 1300oC and holding time of 5 to 30 min resulted in significantly improved density. Nevertheless sintering temperature of at least 1300oC was required for pore coalescence and high tensile properties.
Authors: T. Shimabukuro, R. Daouk, J. Skupnjak, M. Nordman, M. Burrell, L. Sutanto, A. Abad, Hamid Garmestani, N. Ula, J. Foyos, K. Almahmoud, O. Almahmoud, O.S. Es-Said
Abstract: Three Ti-6Al-4V plate materials produced by powder metallurgy technique, included pre-alloyed hydride-dehydride (HDH) plate rolled to 75% reduction in thickness, and two blended elemental (BE) powder plates rolled to 75% and 87% reduction were evaluated. The objective of this study was to determine differences in microstructure and toughness between the pre-alloyed HDH and BE Ti-6Al-4V materials processed to the same product form. Heat treatments were performed below the beta transus temperature at 982, 871, 760, and 732°C (1800, 1600, 1400, and 1350°F) for 1, 2, and 4 hours in order to determine differences in heat treating response, and above the beta transus at 1076°C (1970°F) to determine the transformation temperature. The samples were evaluated by optical microscopy and scanning electron microscopy. Charpy impact testing was performed in order to determine differences in the energy absorbed during fracture. Pole figures (0002) of selected conditions were also performed in order to determine any differences in texture between the various conditions.
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