Determination of Hot Extrusion Parameters in a Spray-Formed Ultrahigh-Strength Aluminum Alloy

To determine a suitable industrial extrusion process, the hot deformation behavior of a spray-formed ultrahigh-strength aluminum alloy was studied with a series of isothermal compression tests. The temperature range was from 340 to 480 °C, while the strain rates ranged from 0.001 to 1 s⁻¹. The flow stress behavior was studied, and the activation energy map showed the deformation difficulty degree under different compression conditions. The dynamic materials model processing map displayed three high-efficiency domains and two low-efficiency domains. As a result of the microstructure observations, it was determined that the high-efficiency domains were related to dynamic recrystallization, superplasticity and cracking. The optimum processing conditions were at intermediate temperatures from 410 to 430 °C and strain rates from 0.008 to 0.06 s⁻¹. In light of the extrusion calibration, the practical extrusion condition was determined to be 410 °C/0.03 s⁻¹. The surface morphology and microstructure after practical hot extrusion were consistent with the prediction by the processing maps and calibration.