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As the initiative thermal protection materials applied in the field of aerospace industry, the high temperature performance evolution of the dissipation thermal protection materials is essential for keeping the carrying capacity of structure and the integrity of aerodynamic configuration in the aerodynamic environment. In this paper, flexural properties and compression properties of Mg–Zn/Graphite dissipation thermal protection materials are studied by three point bending tests and compression tests from room temperature to 1000°C, and fracture morphologies are observed and analysed by scanning electron microscope. The results showed that the flexural strength and compressive strength of composites were higher than that of matrix by 115 and 84% at the room temperature. With the increasing temperature, the strength of composite showed a downward trend. The fracture scanning showed that the internal defects of composite increased owing to oxidation of metal during the heating process. However, the t...

Most materials will expand upon heating, while rare ones contract. Such negative thermal expansion materials have great potential in controlling thermal expansion composites. Squeeze casting was used to fabricate fully dense 60 vol.-%Y2W3O12/Al composite in this study. The results showed that negative thermal expansion Y2W3O12 was not reacted with Al due to advantage of squeeze casting fabrication. Upon coefficient of thermal expansion (CTE) test, the composites showed the CTE is significantly larger than predicted from theory. Different sizes of particles were chosen to fabricate high volume ceramic reinforced metal matrix. The thermal expansion of composite shows complex transition with the change of temperature. On the basis of X-ray diffraction, some peak vanishing in composite is shown to result from the thermal mismatch stress between matrix and reinforcement.

In situ SEM observation was carried out during the whole quasistatic compression process to investigate the energy absorption mechanism of fly ash/aluminium syntactic foam. The results indicate that the damage appeared on the wall of cenospheres, leading to a local stress concentration, and then a crack band formed. Once cenospheres were collapsed layer by layer along the crack band, the syntactic foam engendered visible macroplastic strain at a near constant stress level. The macroplastic strain was caused by the collapse of cenospheres, which is the main mechanism of aluminium matrix syntactic foam as an energy absorption material.

Hollow microspheres are usually used as a lightweight filler in syntactic foams. In this work, Al2O3 sols were selected and prepared under optimised conditions. A layer of Al2O3 film was prepared on hollow glass microspheres by the sol–gel process. The phase and element evolution of Al2O3 gel powders during exsiccation and heat treatment was investigated by infrared spectroscopy (IR) and X-ray diffraction (XRD). The 1–3 layers of coatings were prepared using a dipping method and characterised by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The results show that clear stable sols can be obtained at 80–90°C with n(H2O):n(Al3+) greater than 150∶1 and pH 2·7–3·5. After exsiccation, AlOOH, the precursor of Al2O3 sols, can be totally eliminated and turned into Al2O3. Coatings with double layers have the best effect for covering the hollow microspheres.

B4Cp/2024Al composite with volume fraction of 45% was designed and fabricated by pressure infiltration technology. Microstructure and friction and wear properties of B4Cp/2024Al composites were studied. The results show that reinforcement particles are uniformly distributed and a qualified relative density of the composite has been achieved. A high density of dislocations was observed to be in the peripheral area of the reinforcement particles, and a large number of fine acicular precipitates were found. Coefficient of friction of B4Cp/2024Al composites decreased slightly with increasing load and sliding speed, meanwhile, the wear rate increased with increasing load and sliding speed. Main forms of wear in B4Cp/2024Al composites were abrasive wear, adhesive wear and oxidation wear.

The impact of quenching medium on property and the aging behaviour of 45 vol.-%SiCp/2024Al composites manufactured by squeeze casting method have been investigated. With increasing cooling rates, the hardness increased and the relative rate of change decreased. The quench sensitivity of composites has been attributed to several mechanisms: intermediate precipitation and dislocation strengthening. The effect of cooling rate on GP zone formation is smaller. The formation of intermediate precipitates and dislocation strengthening will be more dominant.