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Near-net shape forming of the hollow sphere joints (60 mm in diameter) used in large space truss structure of spacecraft was realised by powder injection molding and diffusion bonding. For metal injection molding (MIM) process, two binder systems based on polyoxymethylene (POM) and paraffin wax (PW) are comparatively studied. The powder loading, power law index, viscous flow activation energy and integrated rheological factors of feedstock were systematically studied. Except powder loading, The feedstock based on POM system has a smaller strain and temperature sensitivity (n = 0.368, E = 17.95 kJ mol −1 ) and better rheological properties (α = 6.3). The lowest interstitials contents of as-sintered samples are 0.05 wt-% for C, 0.28 wt-% for O and 0.046 wt-% for N, which meet the Grade 5 PM (Ti-6Al-4V) specifications according to ASTM B988-13. The tensile strength and ductility reach 978 MPa and 6.3%, respectively, after 1300 °C sintering and capsule-free hot isostatic pressing (HIP).

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Powder metallurgy (PM) of titanium hydride (TiH2) has emerged as an attractive alternative to PM of Ti. Microwave (MW) heating has the potential to further facilitate the development of PM TiH2 as TiH2 is essentially a ceramic material. A detailed assessment has been made of the effectiveness of MW heating of Ti-xTiH2 (x =0-100) powder compacts through 30 experiments conducted under a variety of conditions. MW hybrid heating (i.e. when assisted with a SiC MW susceptor) proved to be reliable and consistent in heating Ti-xTiH2 powder compacts and the heating rate increased progressively with increasing TiH2 powder content, indicating that TiH2 powder is more responsive to MW heating than Ti metal powder. However, heating of TiH2 powder compacts by MW radiation without the assistance of a SiC MW susceptor proved to be inconsistent and unpredictable, where successful heating (heated to 1300°C in 20 min) was achieved but many failures also occurred. However, the use of SiC can cause contamination (Si and C). The challenges of heating of TiH2 powder by direct MW radiation were discussed.

In this work, high strength and high wear‐resistant titanium matrix composites (TMCs) reinforced with in situ TiC derived from pyrolysis of polysilazane (PSZ) are fabricated successfully. The processing technology is developed with a novel powder metallurgy method combining solution‐assisted wet mixing and pressureless sintering. The effects of PSZ addition on the microstructure, hardness, mechanical properties, and tribological properties are systematically studied. The TMCs possess better comprehensive properties compared to conventional ex situ methods. The pyrolysis of PSZ leads to the formation of TiC particles and N, Si atoms solid‐solution in the Ti matrix. The microstructure of the composites is homogenous and fine‐grained. The average grain size of α‐Ti decreases significantly from 106.1 µm of pure Ti to 37.2 µm of the 1.5 wt% PSZ/Ti composite. Among these TMCs, the 1.5 wt% PSZ/Ti composite displays comprehensively excellent mechanical properties with the ultimate tensile strength (UTS) of 711 MPa, yield strength (YS) of 568 MPa, and elongation (EL) of 8.0%. In addition, the composite possesses a high wear resistance with a low specific wear rate of 0.355 × 10−12 m3 N−1 m−1 under constant condition (0.03 m s−1, 2N).