Microstructural evolution and mechanical properties of deep cryogenic treated Cu–Al–Si alloy fabricated by Cold Metal Transfer (CMT) process

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Cryogenic treatment is an effective route to obtain fine grained microstructure in materials. In this work, the effect of deep cryogenic treatment (DCT) on the microstructural evolution and mechanical properties of a copper-aluminum-silicon (Cu–Al–Si) alloy deposited by cold metal transfer (CMT) technology was investigated. Copper-rich Cu–Al–Si alloy with ~8.3% aluminum content was deposited on T2 copper substrate using an innovative dual wire feed system based on CMT technology. The deposited alloy was subjected to DCT for varying time duration (0, 6, 12 and 24 h). Evaluation of microhardness and tensile properties showed that the deep cryogenic treatment enhanced these properties. Microhardness increased about 10% with the increase in the DCT time duration. Under tensile loading conditions, the DCT conducted for 12 h provided the best properties, with an increase in both the tensile yield and ultimate strengths (~20% increase). Microstructural evolution and grain orientation were investigated using Electron Back Scattered Diffraction (EBSD). Microstructural studies revealed the formation of subgrains, fine grains and deformation twins due to DCT. Significant grain refinement was achieved due to the increase in the formation of high angle grain boundaries. It is summarized that the deep cryogenic treatment induces microstructural evolution: (i) grain refinement and (ii) texture randomization, and improves the mechanical properties of Cu–Al–Si alloy.