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This article presents a detailed assessment of microwave (MW) heating, isothermal sintering, and the resulting tensile properties of commercially pure Ti (CP-Ti), Ti-6Al-4V, and Ti-10V-2Fe-3Al (wt pct), by comparison with those fabricated by conventional vacuum sintering. The potential of MW sintering for titanium fabrication is evaluated accordingly. Pure MW radiation is capable of heating titanium powder to ‡1573 K (1300°C), but the heating response is erratic and difficult to reproduce. In contrast, the use of SiC MW susceptors ensures rapid, consistent, and controllable MW heating of titanium powder. MW sintering can consolidate CP-Ti and Ti alloys compacted from À100 mesh hydride-dehydride (HDH) Ti powder to~95.0 pct theoretical density (TD) at 1573 K (1300°C), but no accelerated isothermal sintering has been observed over conventional practice. Significant interstitial contamination occurred from the Al 2 O 3 -SiC insulation-susceptor package, despite the high vacuum used (£4.0 9 10 À3 Pa). This leads to erratic mechanical properties including poor tensile ductility. The use of Ti sponge as impurity (O, N, C, and Si) absorbers can effectively eliminate this problem and ensure good-to-excellent tensile properties for MW-sintered CP-Ti, Ti-10V-2Fe-3Al, and Ti-6Al-4V. The mechanisms behind various observations are discussed. The prime benefit of MW sintering of Ti powder is rapid heating. MW sintering of Ti powder is suitable for the fabrication of small titanium parts or titanium preforms for subsequent thermomechanical processing.

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A series of Al-Ga-In-Sn-NaCl composites were prepared by mechanical ball milling. NaCl contributes to the particle breakage and particle refinement during the ball milling process, but the hydrogen generation of the composites decreases as the content of NaCl exceeds 5%. Higher composite to water ratio led to reduction of the hydrogen generation for the Al-Ga-In-Sn-5% NaCl composite. In addition, compared to pure water, the hydrogen generation of this composite is lower in NaCl solution. These results indicate the higher ionic concentration in water is not conducive for hydrogen generation. During the hydrolysis process, the dissolution of NaCl in water increases the ionic concentration, so the excessive NaCl in the composite leads to the reduction of hydrogen generation. In addition, optimization of the milling time is important for hydrogen generation. By optimizing the milling time to 18 hours, hydrogen yield of the Al-Ga-In-Sn-5% NaCl composite reached 1150 mL g −1 at 25 C. Although the composites easily react with moisture in the air, the hydrogen yield of Al-Ga-In-Sn-5% NaCl and Al-Ga-In-Sn-10% NaCl composites can maintain 100% and 94% of the original after being exposed to the air for 5 and 10 days. Highlights 1. A series of Al-Ga-In-Sn-NaCl composites were prepared by mechanical ball milling. 2. NaCl contributes to the particle breakage and particle refinement during the ball milling process, but the hydrogen generation of the composites decreases as the content of NaCl exceeds 5%.3. By optimizing the milling time to 18 hours, hydrogen yield of the Al-Ga-In-Sn-5% NaCl composite reached 1150 mL g −1 at 25 C in pure water. 4. The hydrogen yield of Al-Ga-In-Sn-5% NaCl and Al-Ga-In-Sn-10% NaCl composites can maintain 100% and 94% of the original after being exposed to the air for 5 and 10 days.