A Heat-resistant Rare Earth Magnesium Alloy and Its Heat Treatment Process for Castings with Uneven Wall Thickness

Abstract

The invention discloses heat-resisting rare earth magnesium alloy and a thermal treatment process for an uneven-wall-thickness casting of the heat-resisting rare earth magnesium alloy. The heat-resisting rare earth magnesium alloy is composed by Y, Nd, Ag, Zr, Gd, and the balance Mg and inevitable impurity elements. The thermal treatment process includes the steps that the uneven-wall-thickness heat-resisting rare earth magnesium alloy casting of a complex structure is heated to 530-540 DEG C, and after heat preservation and solid solution, the casting is cooled to the room temperature at the speed of 90 DEG C / min or more; and then the casting is heated to 220-230 DEG C, and after heat preservation and artificial aging, the casting is discharged out of a furnace and air-cooled. The heat-resisting rare earth magnesium alloy is reasonable in component ratio, the process is simple, and operation is convenient; during implementation, only conventional thermal treatment equipment is needed, the technological process is simple, practicable, safe and reliable, and the thermal treatment process is suitable for treating large-size rare earth magnesium alloy castings which are complex in shape and have differences in wall thickness; a feasible scheme is provided for improving the performance of the complex-structure rare earth magnesium alloy castings for aviation and spaceflight, the using requirements for parts of the field of aviation and spaceflight are met, and industrial production is facilitated.

Description

technical field [0001] The invention belongs to the technical field of heat treatment of magnesium alloy materials, and relates to a heat treatment process of a heat-resistant rare earth magnesium alloy and castings with uneven wall thickness thereof, in particular to the heat treatment of Mg-Y-Nd-Ag series rare earth magnesium alloy castings. Background technique [0002] Mg–Y–Nd alloys are one of the typical representatives of rare earth magnesium alloys. Due to the multiple effects of rare earth elements, Mg 24 Y 5 , Mg 2 Y, Mg 41 Nd 5 and Mg 14 Nd 2 Compounds such as Y have good heat resistance and high strength, and are widely used in the manufacture of structural devices that require high temperature service in the fields of aviation and aerospace. At present, the rare earth magnesium alloy structural parts used in aviation and aerospace are mostly formed by low-pressure casting for large size, complex shape, and different wall thickness. Segregation forms a lar...

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Problems solved by technology

However, using the existing heat treatment system to heat treat large and complex Mg–Y–Nd series rare earth magnesium alloy castings for aviation and aerospace, due to the large difference in thickness at each position of the casting, the heating process is uneven at each position, and the alloy The type and structure of the precipitation strengthening phase are different, and the corresponding suitable precipitation temperature and peak precipitation time are also different, resulting in uneven size of the precipitated phase, and finally manifested as uneven mechanical properties of the thin-walled and thick-walled castings after heat treatment. Even the high temperature strength cannot meet the requirements of use, and the disadvantages of low plasticity

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