Microstructural features and properties of high-hardness and heat-resistant dispersion strengthened copper by reaction milling

Abstract

The oxide dispersion strengthened copper alloys are attractive due to their excellent combination of thermal and electrical conductivities, high-temperature strength and microstructure stability. To date, the state-of-art to fabrication of them was the internal oxidation (IO) process. In this paper, alumina dispersion strengthened copper (ADSC) powders of nominal composition of Cu-2.5 vol%Al 2 O 3 were produced by reaction milling (RM) process which was an in-situ gas-solid reaction process. The bulk ADSC alloys for electrical and mechanical properties investigation were obtained by sintering and thereafter hot extrusion. After the hot consolidation processes, the fully densifi ed powder compacts can be obtained. The single γ-Al 2 O 3 phase and profile broaden effects are evident in accordance with the results of X-ray diffraction (XRD); the HRB hardness of the ADSC can be as high as 95; the outcomes should be attributed to the pinning effect of nano γ-Al 2 O 3 on dislocations and grain boundaries in the copper matrix. The electrical conductivity of the ADSC alloy is 55%IACS (International Annealing Copper Standard). The room temperature hardness of the hot consolidated material was approximately maintained after annealing for 1 h at 900 ℃ in hydrogen atmosphere. In terms of the above merits, the RM process to fabricating ADSC alloys is a promising method to improve heat resistance, hardness, electrical conductivity and wear resistance properties etc.

Differences of the microstructural evolution of Cu powder during continuous and interrupted mechanical milling

“…The presence of these defective structure decreases the diffusion distances and increases the diffusivity of oxygen absorbed on the particle surface into the copper matrix at low temperature as interstitial and substitutional atoms. Besides, the slight raise in temperature during milling aids the oxygen diffusion, and consequently, selective reaction takes place among the copper and oxygen atoms [13]. Unfortunately the oxygen content measured by LECO is affected by the amount of oxygen present on the powder surface, so actual oxygen dissolved in the copper matrix is unknown.…”

“…It has been shown that the reaction rate of oxidation is enhanced and dynamically extended during the milling as a result of mixing processes and microstructural refinement [10]. Therefore the presence of oxygen in the MM system could affect severely the chemical, physical and mechanical properties of the final product [9,[11][12][13][14]. Parameters such as milling time, process control agent or the choice of a continuous or interrupted cycle determine the characteristics of the milled powders and the level of oxygen absorbed [15,16].…”

Microstructure of Glidcop AL-60

“…The peaks of α-Al2O3 have peak width (FWHM) in the order of 0.1° which are considerably sharper than those of η-Al2O3 with FWHM in the order of 1°, indicating significantly larger particle size of α-Al2O3. Both α-Al2O3 and η-Al2O3 have been observed in internal oxidation ODS copper [9], [13], [16], [17], [20]. In principle, the particle sizes can be analyzed by XRD peak width by using Scherrer equation.…”

Microstructures and Tensile Mechanical Properties of Consolidated Copper

“…Due to these favourable atrributes, powder metallurgy copper and copper alloy products are widely used in automotive, appliance, electronics, communication and other areas, and thus play an important role in industrial production [7][8][9][10][11][12] . Compared with conventional sintering methods, the spark plasma sintering (SPS) can save energy and time, improve the equipment efficiency.…”