Study On Heat Resistant Magnesium Alloy Synthesized Via In-situ Ultrasonic-chemistry Reaction And Its Mechanical Properties

In this paper, rare earth elements Sm and Mg-Al system AZ61magnesium alloywas the main object of study, synthesized Al2Sm/AZ61heat resistant magnesiumalloy via in-situ ultrasonic-chemistry reaction, researched the effects of high-energyultrasound process parameters on the solidification structure and the mechanicalproperties of the Al2Sm/AZ61alloy, discussed the impact mechanism of theultrasound technology on Al2Sm particles and fine-grain strengthening mechanism ofthe Sm in the magnesium alloys. Ultrasonic time, ultrasonic power, rare earth contentwere putted as variables for optimal combination of orthogonal experimental programto obtain the optimal preparation route and parameters of the Al2Sm/AZ61alloy viain-situ ultrasonic-chemistry reaction. The orthogonal experimental result showed thatthe optimum process was2.0%rare earth with750W ultrasonic power for110s, theAl2Sm/AZ61alloy grain and the Al2Sm particles were the smallest, Al2Sm particlesuniformly distributed in the melt. The tensile strength and elongation at roomtemperature reached399MPa and8%, the tensile strength and elongation at elevatedtemperatures reached298MPa and16.5%. Researching the effect of heat treatment onthe hardness of the Al2Sm/AZ61magnesium alloy, we found that the hardness ofAZ61-2%Sm-750W alloy increased by10%after400℃+22hours solid solution and200℃+20hours aging.This paper discussed the effect of the content of the Sm on AZ61magnesiumalloy, and analyzed the major role of the rare earth Sm in AZ61. With the increasingof the content of the Sm, the size and number of β-Mg17Al12phase would decreasealong the grain boundary, Al2Sm intermetallic distributed in the grain boundary; withthe adding of the Sm, the grain size of the AZ61would decreased, in this paper,AZ61-1Sm had the minimum grain. The maximum of the yield strength and ultimatetensile strength respectively were142MPa and215MPa with the1%Sm in the alloy.The improvement of the ultimate tensile properties was mainly attributable to thegrain refinement, solution strengthening and dispersion strengthening of the smallAl2Sm phase. When the content of Sm was1.5%in the AZ61, the elongation was preferably.This paper also researched the effect of the ultrasound on Al2Sm/AZ61magnesium alloy, and analyzed the influence of the mechanism of high-energyultrasound. The size of the Al2Sm phase was about13μm without ultrasoundtreatment, while the size would drops to about6μm with ultrasound treatment; thehigh-energy ultrasound would produce the high pressure and high temperature ofabout1446MPa and104k, which would make the semi-continuous net-structureMg17Al12phases fuse and the conglomeration Al2Sm crushed into fine particulate.The maximum velocity of the spraying jet which was produced by the acousticstreaming was2.5m/s, which was favor of the small Al2Sm macroscopic particlesuniformly dispersed throughout the melt.