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Isothermal hot compression tests were conducted on the 6063 aluminum alloy using a Gleeble-3810 thermal simulator at four different strain rates (0.01, 0.1, 1, and 10 s–1) and five different temperatures (300, 350, 400, 450, and 500°C). Based on the constitutive relationship to process the experimental data, processing maps were produced to evaluate the efficiency of power dissipation (η) and identify regimes with flow instability. Processing maps were produced for two regions with relatively high η at a strain of 0.6, namely (300–320)°C/(0.01–0.02) s–1 and (400–500)°C/(0.01–1) s–1. There were also two unstable regions at (300–325)°C/(0.06–1.5) s–1 and (350–500)°C/(3–10) s–1. The microstructures observed by optical microscopy and electron back-scattered diffraction maps indicated that the deformed samples only underwent dynamic recovery under deformation conditions of (300–320)°C/(0.01–0.02) s–1, while at 500°C/0.01 s–1 the samples showed a high degree of dynamic recrystallization and then produced new equiaxed fine grains. At high strain rates, the precipitates had a pinning effect on dislocations, leading to stress concentration. Local plastic deformation occurred, resulting in thermoplastic instability. Therefore, the optimum processing conditions for the 6063 aluminum alloy determined from true stress-strain curves, processing maps, and microstructural analysis were 500°C/0.01 s–1. [ABSTRACT FROM AUTHOR]