Preparation of lanthanum-containing AE heat resisting die-casting magnesium alloy

Abstract

The invention relates to a lanthanum contained AE series heat-resistant die-casting magnesium alloy and a preparation method thereof. The alloy consists of the following compositions by mass percentage: 3.5 to 4.5 percent of Al, 1 to 6 percent of La, 0.2 to 0.6 percent of Mn, and less than 0.03 percent of gross of impurity elements Fe, Cu and Ni, and the balance being magnesium. The method comprises the following steps: preheating pure magnesium, aluminum, aluminum-manganese interalloy and magnesium-lanthanum interalloy to the temperature of 200 DEG C according to a proportion; then, putting the mixture into a crucible which is preheated to the temperature of 300 DEG C, and introducing shield gas with a volume ratio of SF6 to CO2 being 1:100; adding the magnesium-lanthanum interalloy into the crucible after melt reaching a temperature of between 720 and 740 DEG C; continuously introducing the shield gas to stir the melt for 5 to 10 minutes; introducing argon gas to refine the melt for 5 to 10 minutes; and keeping the mixture stand for 28 to 32 minutes to obtain the lanthanum contained AE series heat-resistant die-casting magnesium alloy. The alloy has tensile strength at 200 DEG C of between 119 and 136MPa, yield strength of between 85 and 107MPa, elongation percentage of between 18 and 24 percent, and creep rate under 70MPa at 200 DEG C of 1.17*10<-9>s<-1>.

Description

technical field [0001] The invention belongs to a preparation method of a lanthanum-containing AE series heat-resistant die-casting magnesium alloy. Background technique [0002] Magnesium alloy is the metal structure material with the lowest density in engineering applications. At the same time, magnesium alloy also has the advantages of high specific strength, high damping, electromagnetic shielding, excellent casting, cutting performance and easy recycling. It is used in automobiles, electronics, aviation, aerospace , national defense and other fields have important application value and broad application prospects. Especially in the context of global iron, aluminum, zinc and other metal resources becoming increasingly scarce, environmental protection pressure and energy conservation awareness are increasing, magnesium's resource advantages and performance advantages have been fully utilized, and magnesium alloys have become a rapidly rising engineering material. Two Mg-...

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Problems solved by technology

However, subsequent related reports showed that when the temperature is higher than 150 °C, Al 11 RE 3 phase partially decomposes and leads to Mg 17 Al 12 The formation of the phase makes the structure near the alloy grain boundary unstable during the creep process, which eventually leads to a sharp decline in the creep resistance of the alloy.

In 2005, the new high-temperature creep-resistant die-casting magnesium alloy AE44 developed by Norway Hydro Magnesium Company has been used in the production of auto parts, such as the engine bracket of the car, but because the rare earth added in the alloy is also cerium-rich rare earth, so the alloy is in high temperature. The root cause of the decrease in creep performance at 150°C is Al 11 RE 3 Partial decomposition of phases and not fully resolved

Therefore, the AE series die-casting magnesium alloy with the addition of ordinary cerium-rich mixed rare earth cannot meet the requirements of the alloy used at a higher temperature of 200 °C

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