Effect of wall thickness on the precipitation behavior, microstructure, electrical conductivity and mechanical properties of copper alloy prepared by electron beam powder bed fusion

Abstract

Electron beam powder bed fusion (EB-PBF) is one of the most promising technologies for preparing thin-walled copper alloy, because copper alloy have a high energy absorption rate for electron beam, and high preheating temperature can reduce the solidification temperature gradient and reduce the deformation of thin-walled parts. At present, there are few reports on the systematic research work on the EB-PBF of thin-walled CuCrZr alloy parts, and it's impossible to effectively supervise the production of complex thin-walled CuCrZr alloy parts. This work aims to investigate the effect of thickness on the microstructure and mechanical properties of CuCrZr alloy produced by EB-PBF. As the wall thickness decreases from 5.0 mm to 0.3 mm, the grain sizes of the XY and YZ planes decreased from 20.4 μm and 43.1 μm to 14.5 μm and 21.5 μm respectively, and the texture intensity decreased from 16.04 and 23.57 to 7.62 and 10.99. The analysis showed that Cr₂O₃ nanoprecipitates were precipitated in situ in the sample, and their average size decreased from 65.8 nm to 21.6 nm. Due to the reduction in grain and nanoprecipitate size, the performance of thin-walled samples is significantly enhanced, with yield strength (YS) increasing from 112 MPa to 165 MPa and conductivity increasing from 71.7 %IACS to 86.1 %IACS. Finally, the main contributions to the YS of specimens with different wall thicknesses was discussed. Precipitation strengthening and dislocation strengthening are the main strengthening mechanisms in thin-walled samples, and the gradual refinement of nano-precipitates is the main reason for the improvement of mechanical properties as the wall thickness decreases.