Properties Research Of Die-casting AZ91 Mg Alloy Based On Carbon Nanotube Composites

This paper mainly researches the preparation of Carbon nanotubes AZ91 magnesium alloys with adding multiwalled carbon nanotubes (MCNTs) block with plunger under the condition of die casting method and discussed effect of the content of carbon nanotubes and precast block milling time on mechanical properties, corrosion resistance, antiwear properties of AZ91 magnesium alloys。It has been studied that CNTs adding amount influences on grain sizes of AZ91 magnesium alloy thinning as-castings. The grain morphology and microstructure were observed by means of metallographic microscope and SEM; It has been tested tensile strengthes, elongations and microhardnesses for AZ91 speciamen with different adding amount of mwcnts and fabricated with different precast blocks that were made for different milling time; It was observed mwcnts distribution respectively in a preform with different balling time and AZ91 based mwcnt composites added with different preform via an electron microscopy (SEM); It has been researched that the content of carbon nanotubes and precast block milling time effect on corrosion resistance of AZ91 magnesium alloys using the weight loss, PH value change, electrochemical polarization curve method; It has also researched that content of mwcnts effect on abrasion resistance properties of AZ91 magnesium alloys, measuring surface weight loss, observing surface wear morphology, wear form and the morphology of honing。The results of the study show that grains of AZ91 magnesium based mwcnts composites can be refined, The sizes of the die casting's grains are about 10-40 u m; Adding mwcnts can improve the tensile strength of AZ91 magnesium alloys, when the adding amount of mwcnts is below 1.5wt%, the tensile strength of die cast AZ91 is about 194MPa, increased by 26.8% than that of matrix。But the tensile strength fells down with the increase of the adding amount of mwcnts due to the aggregation of mwcnts in a metal melt while adding amount of mwcnt is greater than 1.0wt%, and the elongation reached maximum at the adding amount。The microhardness and tensile strengthes trend as the same。Mwwcnts milling time is longer, the dispersion is better; When the time reaches 16hrs, mwcnts can wrap evenly around Al powder; Adding mwcnts can obviously improve the corrosion resistance of AZ91 magnesium alloys.Their average corrosion rate is the best, reaching 0.2756/(m2·s) while the mwcnt adding amount is 3.0 wt%. The pH value go up rapidly at the start, subsquently the PH gradually changed up slowly during corrosion; Using electrochemical corrosion experimental analysis results can clearly demonstrate that adding mwcnts can make the balance potential shifting to right and the corrosion current dessity down so as to improve the corrosion resistance proprety, displaying the consistent of the weight loss and PH change; In a certain range, with the increase of the adding amount of mwcnts, AZ91 magnesium alloys antiwear ability increases, which shows that mwcnts in the matrix can more effectively resist wear from friction pair, so as to improve the antiwear properties of AZ91 magnesium alloy; Fracture of die-cast AZ91 magnesium based mwcnt composites are brittle fracture and also shows cleavage fracture after heat treatment。...