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Microstructure and properties of α + β brass after ECAP processing

Dutkiewicz J., Masdeu F., Malczewski P., Kukuła A.

Archives of Materials Science and Engineering

2009

Vol. 39, nr 2

80-83

Purpose: Purpose of this paper is to determine the effect of Equal Channel Angular Pressing (ECAP) processing on the microstructure and hardness of α + β ?brasses. The effect of deformation temperature and number of passes was investigated particularly on the shape and size of grains of both phases. Design/methodology/approach: The specially constructed channel with 90° pressing angle, allowing heating of the tool with the sample was used for ECAP processing. The grain size was investigated using optical and transmission electron microscopy. The hardness and measurements microhardness were used to determine the effect of ECAP on the hardness of both phases. Findings: Significant grain refinement down to 300 nm from the initial 20 mm was observed after ECAP processing at 300°C. At 400°C grain refinement occurred down to 1-3 mm. Frequent microtwins were observed within aphase. The microhardness of the αphase was higher than that of αphase, 235 HV and 173 HV respectively. Research limitations/implications: The limitation is a size of the sample which makes difficult future applications. Another one is elevated temperature (minimum 300°C) otherwise the samples forms crack. This limits also the grain refinement which is above the range of nanomaterials. Practical implications: Significant grain refinement allows to increase the hardness and strength of the sample preserving a good plasticity. The limitation is the size of the channel what limits the application. The material could be used in such cases when high strength of brasses is needed with sufficient plasticity and good conductivity. Originality/value: In this paper detailed TEM studies were performed for α + β brasses showing high density of microtwins and higher density of dislocations within ? phase, than in the bphase. Higher hardness of the bphase results from the ordering, which hinder deformation of this phase.