The effect of cryogenic cooling and cold deformation on microstructural features of solution annealed CuNi3SiCr alloy

In this study, the effects of both the quenching medium (water and dry ice) and cold deformation (30%) on the structural properties of commercially extruded CuNi3SiCr alloy following solution annealing (900°C, 1 h) are investigated. The phase structure is monitored by microscopic examination for the alloy with variable conditions, and the crystallite size, microstrain and dislocation density of the materials are calculated depending on the condition. Metallurgical characterization studies indicate the presence of metal silicides (Ni2Si and Cr3Si) in homogeneous distribution within the α-copper matrix of the extruded alloy and the grains elongate due to cold deformation. Although the cooling with dry ice shows no significant change in the crystallite size of the alloy compared to the cooling in water, an increase in microstrain and dislocation density is detected. Electrical conductivity and hardness measurements reveal a significant change in the hardness of the alloy due to cryogenic and deformation effects. Also, EBSD recrystallization and GOS map studies show the energy stored in the alloy increases due to increased cooling efficiency and deformation. All these findings reveal how cryogenic cooling, and cold deformation affects (i) physical and mechanical properties, (ii) the precipitation kinetics during aging and (iii) the recrystallization tendency of the CuNi3SiCr alloy.