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The isothermal compression tests of Al–5Ti–1B master alloy were conducted on the thermal mechanical simulator Gleeble-1500D at the deformation temperature range of 300–450 °C, the strain rate range of 0.01–10.00 s-1, and the engineering strain of 50 ％. The effects of deformation temperatures and strain rates on the flow stress were analyzed by the true stress–true strain curves. The result indicates that the flow stress increases with the increase of strain rate, while it decreases with the increase of temperature. The hot deformation activation energy of Al–5Ti–1B master alloy is calculated to be 250.9 kJ·mol-1, and the constitutive equation is established asε = 1.97 × 1019 sinh(0.015σ)[ ]11.14exp(-250.9/RT), and the validity of this constitutive equation is verified. Based on dynamic material model (DMM) criterion, the hot processing map of Al–5Ti–1B master alloy is obtained. The optimum hot extrusion conditions are determined as deformation temperature of 400 °C and strain rate of 1.00 s-1, and the flow instability only appears at the tem-perature range of 300–340 °C at the base of the hot pro-cessing map.