Effect Of Multi-direction Forging Process On Microstructure And Mechanical Properties Of ZK60 Magnesium Alloy

Multi-direction forging was performed on the solution ZK60 magnesium alloy at constant temperature or psyctic temperature for different passes, and gained microstructure significant refined. This paper studied the effect of the multi-direction forging process parameters on the microstructure of ZK60 magnesium alloy, also the tensile deformation behavior of the solution and forged ZK60 magnesium alloy at room-temperature were investigated.There is second-phase existing in as-cast ZK60 magnesium alloy, and it makes plasticity reduce in deformation process. And we should eliminate the effect of second-phase through solution treatment. With the extension of holding time and rise of heating temperature, solution treatment can be seen as a process of refinement of grain boundary and growth of grain. After holding 16 hours in 330℃, ZK60 magnesium alloy obtains the better mechanical properties, the ultimate tensile strength is about 230 MPa and the elongation to failure increased by 2.8 times compared with the cast. So the scheme of solution treatment is selected to holding 16 hours in 330℃.Multi-direction forging was performed on the solution ZK60 magnesium alloy at different temperature. When the deformation temperature was 250℃, the alloy fractured, and while temperature reached 300℃to 400℃, forging can be completed. After MDF for one pass at 300℃, the texture was twin mostly. After MDF for one pass at temperature above 330℃, dynamic recrystallization took place and the grain size was refined to about 2μm. And magnesium alloy obtained the better mechanical properties after MDF for one pass at 330℃, the ultimate tensile strength was about 271.2 MPa and the elongation to failure reached 9.5%.Multi-direction forging was performed on the solution ZK60 magnesium alloy at 300℃,330℃and 350℃for different passes. With the pass increasing, the variance of size between recrystallization grains was not significant, the grain size was refined to about1-2μm. And the volume fraction of recrystallization was increasing gradually, after forging six times in 350℃is about 70 percentage, and after forging six times in 330℃reached 85 percentage or so. As the effect of texture and the grain size, the elongation to failure increased and the ultimate tensile strength had a slight decrease. The elongation to failure reached 27.4 percentage after forging six times in 350℃,23.4 percentage after forging six times in 330℃and 17.8 percentage after three times in 300℃.While the dependent variable increased to 0.5 and 0.7, speed of refining process raised. After forging four times with the dependent variable 0.5, sample got refined microstructure of high degree. And after forging three times with the dependent variable 0.7, the volume fraction of recrystallization reached 95 percentage and the grain size was refined to about 1μm. The variation range of strength was not huge and elongation was distinctly improved, the elongation to failure reached 34 percentage after forging four times in 350℃with the dependent variable 0.5 and 24.3 percentage after forging three times in 350℃with the dependent variable 0.7.MDF was performed on the solution ZK60 magnesium alloy with the temperature decreasing from 350℃to 330℃for six passes. The volume fraction of recrystallization reached to 80 percentage, and the grain size was refined to about 2μm. Compared with sample after forging six times at the constant temperature of 350℃, various performance had a little increase, especially the elongation to failure reached 33.7 percentage. And the sample after forging six times at the temperature decreasing from 330℃to 300℃had microstructure of higher refined degree, the volume fraction of recrystallization reached 95%.