Study On Alloy Phases Of ZK60 Wrought Magnesium Alloy

It is the crucial factor determing the mechanical properties of magnesium alloys that the morphology, categories, amount, size, distribution and crystallology orientation relationship (OR) of the alloy phases. However, the research of the magnesium alloy phases is not far matureer than that of other metal materials, such as aluminum alloy, steel, and so on. The evolution of the structure is also a lack of more detailed studies. In order to expand the application scope of ZK60 wrought magnesium alloy with high strength, it is necessary to carry out the basic research on its alloy phases.Morphology, category, amount and distribution of alloy phases were studied by using methodologies of metallurgical phase analysis, x-ray analysis and transmission electron microscopy (TEM) in as-cast, solution-treated, as-aged and extruded ZK60 magnesium alloy. The method of indicating electron diffraction pattern was used to identify several main alloy phases, and had a corresponding verification with the self compiling MATLAB programs.The research indicated that the main components of as-cast ZK60 magnesium alloy wereα-Mg, MgZn and MgZn2, while there was a great deal of eutectic structure maked up ofα-Mg and MgZn. The eutectic had various morphologies and distributed in many ways. The solution for 72h at 390℃could effectively reduce the eutectic structure. There were only a few MgZn2 phase and some unknown rod-shaped tempering precipitates which had strict orientation relationship with matrix in solution-treated ZK60 magnesium alloy. MgZn2 phase, in form of parallelogram, 200nm to 500nm in length, having no fixed OR with matrix, was found in as-cast, solution-treated and as-aged ZK60 magnesium alloy as well. MgZn phase, in length of 500nm, had fixed OR ([2201]α∥[1210]β,(0112)α∥(0001)β) with matrix. Mg2Zn3 phase, in form of 100nm short rob, was the most fine phase in terms of size and the most even phase in terms of distribution in ZK60 magnesium alloy. And the same time, the microstructure of ZK60 magnesium alloy aged at 180℃mainly included rod-like MgZn2(β1′) and disc-shaped MgZn2(β2′) precipitates. The precipitation order of ZK60 alloy is G.P.→β1′→β2′→β. After processed by extrusion, there mainly existed MgZn2 phase in ZK60 magnesium alloy with TEM.Based on the MATLAB programs, the selected area electron diffraction was analysied, and the orientation relationship of MgZn2 phase was reasonable forecasted and simulated, which...