Copper has limited application in coils of high magnetic field electromagnets because of its low mechanical strength. In this work, the mechanical strength of copper wire was increased through severe wiredrawing in several steps at 77 K and transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and Vickers microhardness were used to study the evolution of the microstructure of the material. Comparison of the results with those obtained processing the same material at room temperature (295 K) led to a better understanding of the hardening mechanisms. The wires drawn at 295 K showed dynamic recovery structures, while the wires drawn at 77 K showed a partial recrystallization microstructure. The fact that the Vickers microhardness of the wires wiredrawn at 77 K was about 50% higher than those wiredrawn at 295 K suggests that cryogenic deformation was effective in delaying the recovery of the material.

Resumo O objetivo desse trabalho é identificar adequadas condições para o tratamento de envelhecimento de um aço maraging 350, visando evitar a formação de austenita revertida, de modo a maximizar a dureza final do material. Foram utilizadas as técnicas de análise por calorimetria exploratória diferencial (DSC) e difração de raios-X (DRX), as quais indicaram que o tratamento prévio de solubilização pode ser realizado em temperatura pouco superior a 800°C, e que o tratamento de envelhecimento deve ser conduzido com temperaturas entre 450 e 510°C por tempos de até 8 horas. Tais condições seguramente impedem a indesejável formação de austenita revertida durante o tratamento de envelhecimento. Palavras-chave: Aço maraging; Endurecimento por precipitação; DRX; DSC.

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