| Compared with the traditional cast magnesium alloy, spray deposited magnesiumalloy has tiny grain, uniform in microstructure, it can improve mechanical property andcorrosion resistance immensely. Spray deposition technology in preparation of a newtype of high strength, corrosion resistant magnesium alloy has high theoretical andpractical values.Analysis the effects of Nd and Ca on microstructure and properties of spraydeposited Mg-Al-Zn alloy, study on spray deposition of magnesium alloy extrusion billetmicrostructure and properties, study the effect of heat treating regime on mechanicalproperty and micro-structure of the alloy in virtue of hardness testing, OM, SEM, TEM andXRD diffraction analysis. The results of studies show that:The preparation process of spray deposited magnesium alloy after16times extrusionratios under350℃has tiny grain, uniform in microstructure. The second phase of extrudedalloy is distributed equally and densely in the maxtrixNd can obviously improve the alloy organization, make it becomes small, uniform. Thephase composition of extruded alloy are α-Mg phase, Al2Ca phase and a small amount ofMgZn2phase, A large number of Nd solid solution in Al2Ca,it can prevent the secondphase-particles from growing up, make it become more tiny. new second phase(Al2Nd)appeared after the heat treatment of alloys. due to the heat stability of A12Nd is muchhigher, it can block the motion of the dislocations, and raise the strength of magnesiumalloy.In the spray deposition alloys, the hardness of magnesium alloy without Ndincreased firstly and then fell rapidly with the rising of the solid solution temperature, and thehighest hardness of without Nd alloy is108.6Hv after370℃/3h+205℃/24h. The change inhardness of1%Nd alloy is the same as without Nd alloy, Also after370℃/3h+205℃/24h heat treatment up to the maximum118.2Hv. The hardness of2%Nd in370℃/3h+205℃/24h reaches maximum139.4Hv, With the rise of solution temperature, Itshardness did not decrease significantly.The main second phase composition in alloy is Al2Ca, the number of Al2Ca in9%Caalloy is higher than the alloy containing6%Ca. the size of these second-phase particles withhigh melting is0.5μm-1μm, the great the number, the uniform distribution of these second-phase particles, has an important contribution on magnesium alloy. The experiment also observed the new second phase particles, CaZn phase, it also has some influence on thestrength and hardness of magnesium alloy. the hardness of6%Ca and9%Ca magnesiumalloy rise firstly and then fall, and the hardness value of6%Ca increase to the highest118.2Hv and9%Ca increase to the highest125Hv after370℃/3h+205℃/24h. |
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