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In order to control the grain size during hot forming,grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated.Isothermal annealing was conducted on a Gleeble-1500 thermo-mechanical simulator.The mean grain size Dg of each annealed specimen was measured by the quantitative metallography technique.The grain growth kinetics of the Mg-6Zn alloy annealed at 473–623 K was obtained as D D RT tg g404 11-=2.25 ×10 exp(-95450)by the least square linear regression method.The deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary migration.Microscopic observations show that the non-uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to the non-uniform distribution of solute zinc.This indicates that second phase pinning effect plays an important role in microstructure refinement.
In order to control the grain size during hot forming, grain growth behavior of a pre-extruded Mg-6Zn magnesium alloy and its correlation with solute and second phase distribution were investigated. Isothermal annealing was conducted on a Gleeble-1500 thermo-mechanical simulator. The mean grain size Dg of each annealed specimen was measured by the quantitative metallography technique. The grain growth kinetics of the Mg-6Zn alloy annealed at 473-623 K was obtained as DD RT tg g404 11- = 2.25 × 10 exp (-95450 ) by the least square linear regression method. The deviation of grain growth exponent n = 4 from the theoretical value of 2 may be attributed to the presence of solute zinc and second phases which will retard the boundary migration. Microscopic observations show that the non- uniform distribution of grain size for samples pre-extruded or annealed at low temperatures is closely related to the non-uniform distribution of fine and dispersed second phases but not to non-uniform distributio n of solute zinc. This indicates that second phase pinning effect plays an important role in microstructure refinement.