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Lu-α-sialon ceramics containing elongated grains embedded into fine α-sialon matrix were obtained by applying a two-step hot-press procedure. Incorporation of excess Lu 2 O 3 could promote anisotropic growth of α-sialon grains, and the quantity and aspect ratio of elongated α-sialon grains increase with the amount of Lu 2 O 3 addition. The elongated α-sialon grains nucleate and grow epitaxially on the α-Si 3 N 4 core, and the initial precipitation on the core is richer in Lu and Al content than the subsequent precipitation. The obtained Lu-α-sialons possess improved mechanical properties, the Vickers hardness, flexural strength and fracture toughness of the materials with 4 wt%Lu 2 O 3 could reach with value of 22 GPa, 620.4 MPa and 4.8 MPa m 1/2 , respectively. The Lu-α-sialons also demonstrate excellent high-temperature strength due to the presence of the refractory intergranular phase. The strength of the material with 4 wt%Lu 2 O 3 at 1400 °C could retain 87% of its room-temperature strength.

Nanostructured SiB0.5C1.5N0.5 ceramics were formed by two routes of mechanical alloying and consolidated by hot pressing. Nano-sized 6H-SiC, 3C-SiC and BCN were the main phases for two SiB0.5C1.5N0.5 ceramics. For the SiBCN ceramics fabricated from the powders milled by one-step milling, the content of 6H-SiC is higher than that of ceramic fabricated from the powders milled by two-step milling. The flexural strengths for the former and latter were 312.8 MPa and 423.4 MPa at room temperature, respectively. At high temperature, the strengths of the former reduced 8.2% and 28.0% at 1000 °C and 1400 °C, respectively. The reduction rates of strengths for the latter were 11.3% and 38.5%, respectively. The average thermal expansion coefficients of two SiBCN ceramics consolidated at 1900 °C were about 4.5 × 10−6/°C.

Densified Al 2 O 3 /LiTaO 3 (ALT) ceramic matrix composites (CMCs) were fabricated by hot-press sintering in nitrogen atmosphere. Microstructure and mechanical properties of the composites were investigated systematically. High relative density (99.5%) can be obtained when the ALT composites hot-press sintered at 1300 °C with a pressure of 25 MPa. TEM investigation shows that the LiTaO 3 particles remain ferroelectric and 90° domains are present in LiTaO 3 grains. The Al 2 O 3 particles distribute homogeneously in the LiTaO 3 matrix. A high strength of 195.6 MPa and toughness of 2.8 MPa·m 1/2 were achieved in the sintered ALT composites. The strengthening and toughening mechanisms of the ALT composites were discussed.

The precipitation microstructure and the associated hardness and electrical conductivity have been systematically studied in a 7150 alloy during the ageing treatment. The evolution of the GP zones during the one step and the two step ageing processes is discussed in details. Experimental results show that the electrical conductivity of the alloy treated in the two step ageing regime is higher than that of the alloy treated in the one step ageing regime. The two step ageing regime increases the stability of GP I zones and restrains the coarsening of precipitates. During the two step ageing treatment, GP I zones are present when the ageing temperature at the second stage is 160 °C (36 h), which could not be detected in the one step ageing for short times at the same temperature. Both the GP I and GP II zones disappeared after ageing for 4 h at 180 °C. The achievement of the high strength of the alloy is ensured by a large volume fraction of fine GP zones and η′ precipitates.

A six-layer functionally gradient material (FGM) of Ti–TiB–TiB2 was rapidly fabricated by spark plasma sintering (SPS) in vacuum. Both B and TiB2 were used and reacted with Ti to synthesize TiB. Adjusting the content ratio of B to TiB2 in individual layers could control the amount of synthesized TiB by two steps during sintering. The composition and microstructure of the layers in FGM were investigated by XRD, SEM and TEM. The synthesized TiB has needle-like, agglomerated and elongated morphologies. The content of agglomerated TiB increased and that of needle shape TiB decreased with increasing the target TiB volume fraction ranging from 20 to 60%. The elongated TiB was observed in the other two layers with higher target TiB volume fraction, which structure is similar to the agglomerated TiB. The FGM with Ti on one side to Ti–TiB–TiB2 on the other were fabricated at relative low sintering temperature and short dwelling time by spark plasma sintering.

The in situ TiB/Ti–4.0Fe–7.3Mo composites were fabricated by plasma spark sintering (SPS) technique using mechanical alloying of Ti, Fe65Mo and B powder. The effects of sintering temperature on densification of the composites and microstructure of the in situ synthesized TiB were investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). A dense composite was obtained after sintering at 1000 °C for 5 min. Under proper ball milling and SPS conditions in situ TiB reinforced Ti–4.0Fe–7.3Mo composites have been prepared. The in situ TiB showed a typical needle shape grow along [0 1 0] direction. The transverse cross-section of TiB grain is a hexagonal shape with the planes of (1 0 0), (1 0 1) and ( 1 0 1 ¯ ) . The stacking faults in the (1 0 0) plane were observed in the TiB needles.

LiTaO 3 /Al 2 O 3 ceramic composites were fabricated by hot pressing and pressureless sintering, respectively, to investigate the effect of piezoelectric secondary phase on the properties of structural ceramics. Phase constitution, microstructure and mechanical properties of the ceramic composites were studied. LiTaO 3 could stably coexist with Al 2 O 3 during sintering. LiTaO 3 phase was located at the grain boundaries of Al 2 O 3 matrix fabricated by different processing routes. Domain structures were clearly seen in LiTaO 3 , confirming that LiTaO 3 remained hexagonal ferroelectric phase. About 5 vol.%LiTaO 3 /Al 2 O 3 ceramic composite prepared by pressureless sintering at 1300 °C showed an increase in fracture toughness. Energy dissipation due to domain switching was suggested as a toughening mechanism. With the increasing of LiTaO 3 content, the domain switching toughening mechanism was decompensated by the decreased relative density of LiTaO 3 /Al 2 O 3 ceramic composites. For LiTaO 3 /Al 2 O 3 ceramic composites prepared by hot pressing at 1500 °C, the bending strength decreased because of the increased grain size of Al 2 O 3 matrix. The toughening effect due to domain switching was also decompensated by the coarsening of Al 2 O 3 matrix grains, the weaker net-like LiTaO 3 phase and the weaker bonding strength between LiTaO 3 phase and Al 2 O 3 matrix.