Study On The Process And Deformation Behavior Of Porous Aluminium By Powder Sintering

Porous aluminum and aluminum-silicon alloys were prepared by gas-protecting sintering method and spark plasma sintering method in this thesis, respectively. By means of SEM and electro-optical analytical balance, the relationship of process parameters of sintering and pore-forming to micro structure and characteristic was researched. The stress-strain curve of compression deformation was measured. The power absorption and power absorption efficiency of porous Al and Al-Si were investigated. The mechanism of porous Al prepared by powder sintering method was studied. The main contents and results obtained were summarized as follows:1. The effects of process parameters on the structure and characteristics of porous Al prepared by gas-protecting sintering method were explored. The average porosity and absorption capacity increase, while compression strength decreases, with increasing pore-forming medium content or declining pressure. However, cohesion, fluxing medium, temperature and heat preservation time have no obvious effect on porosity and absorption capacity. And the results show that the compression strength increases with increasing fluxing medium content, heat preservation time, sintering temperature.2. The results show that the porous Al with porosity of 45—55%, compression strength of 45~57MPa and average pore size of 30~90μm is prepared under pore-forming medium content of 30.77~35.71wt%, cohesion content of 8.33wt%, fluxing medium content of 1.5wt%, sintering temperature of 620℃, heat preservation time of 25min, and pressure of 25—35MPa by gas-protecting sintering method.3. The effects of sintering temperature and heat preservation time on the microstructure and characteristics of porous Al-Si prepared by SPS method were explored. The higher the temperature is, the higher the average density and compression strength. Nevertheless, heat preservation time has no remarkable effect on porosity and compression strength when it exceeds lmin. The results show porous Al —Si with porosity of 31 —36%, compression strength of 103~145MPa andaverage pore size of 30~70um can be prepared by SPS method under sintering temperature of 475 °C, and heat preservation time of lmin.4. The stress-strain curve of compression deformation of porous Al and Al-Si consist of linear deformation, pore slumping platform and densification. Pore slumping platform lengthens with increasing porosity, and heightens with increasingstrength of neck.5. The effects of stress of platform and porosity on the power absorption of porous Al or Al-Si were studied. In the compression deformation, the stress of platform and power absorption increase with decreasing porosity under the same strain. Not exceeding this stress of platform, the maximum power absorption efficiency raises with increasing porosity.