Study On Microstructure And Mechanical Properties Of AZ80 Magnesium Alloy Tubes By Hydrostatic Extrusion

Magnesium alloy has many advantages, but the low deformation ability restricted its development. Hydrostatic extrusion has unique advantages in terms of processing brittle materials, plastic deformation can be completed by it at lower temperatures. Now, research on application of the technology is obviously insufficient, and its products are mainly bars.This paper was based on the hydrostatic extrusion, experimental study on expansion of alloy deformed tube and annealing process was carried on, systematically. Firstly, AZ80 magnesium alloy was selected as the experimental material, tube was expanding formed successfully through the self-designed test device, annealing process on the deformed tube was developed. Secondly, the influence on AZ80 magnesium alloy microstructure and mechanical properties of tube-expanding hydrostatic extrusion and annealing process was studied, by microstructure analysis, scanning electron microscopy analysis, X-ray diffraction analysis, mechanical tensile and hardness test; the connection between microstructure, composition and mechanical properties under each state alloy was investigated. The tensile fracture morphologies of different states alloys were observed, by scanning electron microscope, fracture mechanism of each state alloy fracture was analyzed and discussed.The experimental results showed that AZ80 magnesium alloy tube processed by expanding hydrostatic extrusion appeared microstructure inhomogeneity, ultimate strength of extruded tube had been greatly improved, elongation just increased a little; annealing made microstructure inside the tube tend uniform, sub-boundaries increased, when holding time was 2.Oh, annealing recrystallization was found, ultimate strength decreased first, after rising, before finally falling, hardness had the same tendency, elongation gradually increased; tube-expanding hydrostatic extrusion and annealing did not change the phase, only the relative content was different; as-cast fracture surface showed brittle intergranular; homogenized fracture was cleavage fracture with certain toughness; extruded fracture was cleavage fracture; with holding time extending, annealed fracture surface had a tendency from the cleavage to quasi-cleavage fracture. The feasibility of expanding-tube hydrostatic extrusion for brittle alloy was verified, technical advantages of the process were highlighted, the foundation for further research and industrial application was set up.