The Influence Of Hydrostatic Extrusion And Annealing On The Structure And Mechanical Properties Of ZK60 Magnesium Alloy

ZK60 magnesium alloy is difficult to process at room temperature and extrusion will make it produce a large number of defects after which need the heat treatment to improve its performance characteristics.So,ZK60 magnesium alloy has been studied in this paper.First,the homogenization heat treatment of ZK60 magnesium alloy billet was carried out,the extrusion process was drafted and the magnesium alloy pipe was manufactured by using hydrostatic extrusion equipment and an extrusion mold designed by ourselves.Second,ZK60 magnesium alloy tube was fully annealed at different times and temperature.Final,the influence on ZK60 magnesium alloy microstructure and mechanical properties of tube-shrinking hydrostatic extrusion,annealing times and temperature was studied by optical microscopy,X-ray diffraction analysis,mechanical tensile and hardness test and so on.The experimental results show that the microstructure of ZK60 magnesium alloy grain was crushed to produce a large number of winding dislocation after hydrostatic extrusion,microstructure uniformity decreases,and has a dynamic recrystallization,grain boundary deposited second strengthening phase,the strength and hardness of ZK60 magnesium alloy greatly increasing,but the elongation rate decreased significantly,and the fracture type had a tendency from the brittle cleavage fracture toughness fracture to toughness fracture;ZK60 magnesium alloy tubes was annealing treatment with the increase of annealing time and annealing temperature,the abnormal grain microstructure of magnesium alloy is gradually reduced,the second strengthening phase gradually dissolved in the matrix,at the same time,magnesium alloy tubes has a dynamic recrystallization,the strength and hardness of magnesium alloy is decreased,the change of microstructure and mechanical properties is more sensitive to the increase of annealing temperature,the fracture type gradually transform from brittle fracture to ductile fracture,which is consistent with the trend of macroscopical elongation.Therefore,when the magnesium alloy tube is required to get a high elongation and a good organizational appearance and try not to reduce the strength of the tube,the full annealing heat treatment process parameters of ZK60 tube is 350?,3.5h.After heat treatment,tensile strength and yield strength of the pipe were 289 MPa and 196 MPa respectively,and the elongation was 19.3%.