Microstructure and mechanical properties of AZ31 and ZK60 magnesium alloys processed by open die forging

In the present investigation, open die forging tests have been conducted for AZ31 and ZK60 Mg alloys. Microstructure and mechanical properties of the forged Mg alloys have been investigated. Cylindrical specimens with a diameter of 18mm and a height of 18mm were forged in a temperature range of 323 to 673K. The forged specimens of both Mg alloys had good surface quality at high forging temperatures of more than 573K. Microstructural observation revealed that grains were recrystallized by hot forging, though unrecrystallized grains were partially found. The recrystallized grain area for AZ31 was larger than that for ZK60. The mean size of the recrystallized grains decreased with decreasing forging temperature. In particular, a very small grain size of about 3μm was attained by forging at 473K. As a result of tensile tests, it has been found that ultimate tensile strength and 0.2% proof stress of the forged Mg alloys increased with a decrease in forging temperature. This was related to grain refinement by hot forging