Internal oxidation is a commercial method for producing oxide dispersion strengthened copper (ODS Cu). In this paper, the dilute Cu-Al alloy powders containing 0.26 wt% of Al have been internally oxidized at temperatures (T) from 700 to 1000 C, for holding times (t) up to 10h. The alumina particle size has been observed and determined by electron microscopy using the two-stage preshadowed carbon replica method. By the use of backpropagation network, the non-linear relationship between internal oxidation process parameters (T) and alumina particle size has been established on the base of dealing with the experimental data. The results show that the well-trained backpropagation neural network can predict the alumina particle size during internal oxidation precisely and the prediction values have sufficiently mined the basic domain knowledge of internal oxidation process. Therefore, a new way of optimizing process parameters has been provided by the authors.

Alumina dispersion strengthened copper (ADSC) alloy was produced by internal oxidation. The hardness, ultimate tensile strength and elect rical conductivity measurements and microstructure observation on the produced 0.12 %ADSC (0.24% Al2O3, mass fraction) and 0.25%ADSC (0.50% Al2O3 ) subjected to different annealing treatments were conducted. The results show that the microst ructure of the produced ADSC is characterized by an uniform dist ribution of nano2Al2O3 particles in Cu-matrix; the particles range in size from 20 to 50nm with an in terparticle spacing of 30 100nm. The produced 0.12 %ADSC can maintain more than 87% hardness retention after 900℃, 1h annealing treatment; the recrystallization can be largely retarded and is not fully completed even after annealing at 1000℃ for 1h, followed by cold deformation of 84%; local grain growth can be observed after 1050℃, 1h annealing treatment. The results also show that increasing either the alumina content or cold deformation degree increases the hardness of the produced ADSC.

The kinetics of internal oxidation of Cu-AI alloy cylinders, containing up to 2.214mo1% AI, were investigated in the temperature range of 1023 K to 1273 K, and the depth of internal oxidation was measured in the microscopy. A kinetic equation was derived to describe the internal oxidation of Cu-AI alloy cylinders. For the internal oxidation of Cu-AI alloys employed in the synthesis of alumina dispersion strengthened copper, the kinetic equation can be simplified. The derived equation was checked experimentally by means of oxidation depth measurements and the results show that the derived equation is exact enough to describe the kinetics of internal oxidation of Cu-AI alloy cylinders. Based on this equation and the oxidation depth measurements, the permeability of oxygen in solid copper was obtained. Investigation also shows that there is no evidence for preferential diffusion along grain boundaries in the process of internal oxidation.

The mechanisms responsible for the nucleation, growth and coarsening of Al2O3 particles in dilute Cu-Al alloys during internal oxidation have been investigated, and the alumina morphologies produced have been studied by electron microscopy using two-stage preshadowed carbon replica method. The alumina particle size has been observed to increase with increasing temperature of oxidation, with increasing time of oxidation, and with decreasing oxygen resource coefficient over the experimental range. These results indicate that the alumina particle size is determined by a competition between the rate of nucleation as the internal oxidation front passes and the subsequent growth and coarsening rates of the particles.

In the present paper, chromium white cast irons were prepared by the unidirectional solidification. The carbide sample was extracted for the corrosion and wear test. The inter-phase corrosion mechanism and the electrochemical behavior of chromium white cast irons in corrosion medium were discussed from the viewpoints of electrochemistry and erosion wear. The inter-phase corrosion rates between carbide and matrix were obtained for chromium white cast irons. It can be concluded from the investigation that the inter-phase corrosion rate of the alloy is more than half of the total corrosion rate in the medium. The electrochemical behavior of carbide is quite different from the test alloys and the matrixes, and the carbide always is in the self-passive state. The corrosion resistance of type M7C3 carbide is higher than that of type M3C carbide. The free corrosive potential difference between carbide and matrix is the driving force of the inter-phase corrosion. In the present corrosive environment, the carbide is protected, but the matrix is corroded rapidly. Increasing the free corrosion potentials of the matrix can not only reduce the inter-phase corrosion rates, but also raise the corrosion resistance of chromium white cast irons greatly.