| The objective of the paper is to create high strength ultra-fine magnesium alloyMg-3Al-Zn-xY(x=0,0.5,1.0,2.0). The processes are as follows: mechanicalmilling,vacuum hot pressing and warm extrusion and Mg、Al、Zn、Y power are used.The influence of preparation of the alloy during milling time, pressing temperature,extrusion temperature and the influence of Y on the mechanical properties and corrosionbehavior of magnesium alloy were systematic studied. The effective way to improve themagnesium strength and its corrosion resistance was raised.The impact of milling time and the Y content to organizational structure andmorphology of the composite powder in the process of magnesium ball milling underargon atmosphere was studied. Mg-3Al-Zn-xY composite powder of particle less than25μm average, grain size of30~50nm were acquired. SEM is used to analyze themorphology of the composite powder and the effect of Y to Mg-3Al-Zn milling. Al, Zn,Y were dissolved in the Mg matrix, no new phases were found.The Mg-3Al-Zn-xY powder was densified by the technology of vacuum hot-pressand warm extrusion. The effects of hot pressing temperature,extrusion temperature andY composition of composite powder density were studied. The extrusion temperature(150~250℃) increased and the hardness of the material increases; The density of alloyobtained by extrusion reached more than98%.Analysis of TEM shows that the averagegrain size of the alloy extruded ranged from200~300nm.the UFG magnesium alloywere fabricated.The effect of extrusion temperature and Y composition on hardness UFGmagnesium alloys, room temperature tensile and compressive properties were studied.The results showed that Mg-3Al-Zn-0.5Y is the best among magnesium alloys withdifferent Y component extruded at250℃. the maximum hardness is136.87HV; besttensile and compressive properties are the best: a tensile ultimate strength of499MPaand a compressive ultimate strength of535.6MPa. Tensile fracture surface analysisshowed alloys are subject to cleavage fracture.The ultrafine grained Mg-Al-Zn-xY alloy corrosion properties of Y alloy withdifferent contents has been analyzed by using electrochemical workstation Tafel curveand impedance spectrum that alloy after2h immersion. Corrosion morphology were observed by SEM. The results showed that Y did not improve the corrosion resistance ofmagnesium alloy made by powder significantly. On the contrary, the more content ofY,the more corrosion rate of the alloy. |
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