The 1.0%Al2O3/Cu(mass fraction) composite was prepared by hot pressing(HP),then treated by rolling to get a full density. The microstructures and the micro area element distribution of the composite were analyzed by SEM. The density,electric conductivity and tensile strength were also investigated. The experimental results show that the alumina particles are more dispersed and become smaller through a single-pass rolling. The pore existing in the composite is eliminated or closed under the rolling force. The relative density increases from 98.4% to 99.2%. The electric conductivity increases from 88.9%IACS to 91.2%IACS. The tensile strength is increased by 47% from 300 MPa to 440 MPa.
The kinetic characteristics of W grain growth operated by diffusion controlled Oswald ripening (DOR) during liquid phase sintering were studied. A liquid phase sintering of W-15wt%Cu was carried out by pushing compacts into a furnace at the moment when the temperature increased to 1340°C for different sintering times. The results show that liquid phase sintering produces the compacts with considerably low relative density and inversely, rather high homogeneity. On the basis of the data extracted from the SEM images, the kinetic equation of W grain growth, G n = G 0n+ kt, is determined in which the grain growth exponent n is 3 and the grain growth rate constant k is 0.15 μm3/s. The cumulative normalized grain size distributions produced by different sintering times show self-similar. The cumulative distribution function is extracted from the curves by non-linear fitting. In addition, the sintering kinetic characteristics of W-15wt%Cu compacts were also investigated.
Mechanically activated W-Cu powders were sintered by a spark plasma sintering system (SPS) in order to de velop a new process and improve the properties of the alloy. Properties such as density and hardness were measured. The microstructures of the sintered W-Cu alloy samples were observed by SEM (scanning electron microscope). The results show that spark plasma sintering can obviously lower the sintering temperature and increase the density of the alloy. This process can also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders with high density and superior physical properties.
The sintered W-15wt.%Cu alloys fabricated by mechanical alloying were re-sintered under pressure to increase the density and improve the properties of these alloys. The pressure was applied vertically along the axis of the sintered sample. Properties such as density, hardness, and bending strength were measured. The microstructures of the sintered bod- ies were observed. The results showed that the subsequent pressure sintering could increase the density of the sintered W-15wt.%Cu alloys. Their hardness, bending strength, and some other physical properties were also improved by this sub- sequent densification treatment.
LI ZhigangJIA ChengchangSUN LanHE YuntaoFAN Shimin
