This article uses powder metallurgy technology to prepare foamed aluminum and carbon nanotubes (CNTs) / foamed aluminum composites. The laser thermal diffusion analyzer, thermal analyzer, and transfer function sound absorption coefficient test system were used to study the thermal conductivity and sound absorption properties of aluminum foam and its composites, respectively. The results show that the thermal conductivity of aluminum foam with 79% porosity is only 5W · m−1·K−1, which is much smaller than the thermal conductivity of aluminum. So it can be used as an ideal thermal insulation material; The thermal conductivity of carbon nanotubes (CNTs) / foamed aluminum-based composites increases first and then decreases with the increase in the mass fraction of CNTs. As the test temperature increases, the thermal conductivity of the material gradually increases. When the mass fraction of CNTs is 0.75%, the thermal conductivity of foamed aluminum-based composites reaches the maximum. As the test frequency increases, the sound absorption performance of foamed aluminum first increases, then decreases, and then gradually increases, reaching a maximum value around 1000 Hz. The sound absorption performance of CNTs / foam aluminum matrix composites decreases at lower test frequencies as the mass fraction of CNTs increases. At higher frequencies, as the mass fraction of CNTs increases, the sound absorption coefficient of foamed aluminum decreases first and then increases.

In this paper, the microstructure and frictional wear mechanism of iron based high temperature brake friction materials prepared by powder metallurgy are studied. The results show that iron based friction materials are mainly composed of iron matrix, graphite and hard phase. Under the working condition of rotating speed of 6000r/min, the frictional wear mechanism is mainly abrasive wear and slight oxidative wear. Under the working condition of rotating speed of 8800r/min, the frictional wear mechanism is mainly abrasive wear, adhesive wear and oxidative wear.

The material model was established by the finite element analysis software ABAQUS. The temperature field and stress field of iron-based powder metallurgy friction pairs under the brake pressure of 0.44Mpa and 0.8MPa were calculated respectively. The variation laws of temperature and stress under two pressure conditions were compared and analyzed. The results show that with the increase of braking pressure, the stress of the friction pairs increases, but the distribution of temperature and stress fields changes little.

For the iron-based powder metallurgical friction pair under high-speed braking conditions, the structural model and physical model of the friction pair were established, and the finite element software ABAQUS was used to calculate and analyze the temperature field and distribution law of the friction pair during friction braking. The results show that during friction braking, the temperature at the outer diameter of the contact surface of the friction pair is the highest, and the temperature at the inner diameter of the edge of the chip removal tank is the lowest. During braking, the temperature of friction pair increases first and then decreases with time.

Copper-based friction materials with different graphite contents were prepared by powder metallurgy process. The influence of graphite content on the surface hardness of friction materials was studied by Bush hardness tester. By means of scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the wear morphology and composition of friction materials were studied, and the wear mechanism was analyzed. The results show that the graphite content has little effect on the surface hardness of friction materials, and the surface hardness mainly depends on the copper matrix and its alloy elements. The main wear mechanism of copper based friction materials is plough type abrasive wear. Graphite has good lubricity and can reduce the wear.