Heat treatment after forging of magnesium alloy and the properties

Title: Heat treatment after forging of magnesium alloy and the properties Author: Zhu Qian Degree-granting units: Chongqing University Key words: magnesium alloy;; deformation;; microstructure;; mechanical properties;; artificial aging Summary:

Magnesium alloy light weight, high strength, good damping, etc., are widely used in industry, and AZ series magnesium alloys because of its high deformation of the deformation process performance and become the most important industrial application of Magnetic lifter wrought magnesium alloys.

As a "composite molding process of extrusion forging" patented technology part of the study, this paper adopts the aging process hardness testing, metallographic observation, X-diffraction (XRD), tensile test, scanning electron microscopy (SEM) fracture surface analysis methods, focusing on the extruded AZ81, AZ61, AZ61E material by molding deformation and aging heat treatment after molding material during thermal aging behavior, microstructure evolution, changes in mechanical properties and fracture failure mechanism for forming composite extrusion forging process to produce high-toughness magnesium alloy parts lay the basis for regulation and properties.

The results show that:

① isothermal forging can significantly improve the alloy's mechanical properties. In this study, by taking 60% of AZ81 deformation, the deformation temperature at 400 ℃, 5.6mm / s deformation rate conditions on the specimen shape isothermal forging, forging further enhance the strength of the specimens, the tensile strength alloy to 337.6MPa, yield strength of 227.9MPa, extension rate of 15.83%, hardness (HRE) 74.8.

② state isothermal forging material AZ81 at 400 ℃ × 0.5h solution +200 ℃ × 20h artificial aging, the alloy to harden peak (HRE) 86.7, the best mechanical properties, tensile strength alloy to 355.8MPa, the yield strength of 255.28MPa, extension rate of 10.3%. On the mechanical properties after artificial aging analysis, tensile strength and yield strength at first increased, then decreased again with the extended holding time, the elongation is reduced as the holding time has been extended, but at low temperatures reduce the rate of 150 ℃ smallest decrease with increasing temperature the rate is increasing. Alloy phase within the β-Mg17Al12 within the grain and grain http://www.999magnet.com/products/131-magnetic-lifter boundary diffusion precipitation. Room temperature tensile specimen fracture, when the forging into the cleavage fracture toughness after heat treatment fracture ductile-brittle mixture.

③ In the AZ61 prepared by adding rare earth on the basis of the isothermal forging state materials AZ61E solution at 400 ℃ × 0.5h +200 ℃ × 15h artificial aging (T6) treatment, hardening alloy to peak (HRE) 75.8, the best mechanical properties , alloy tensile strength to 304.78MPa, the yield strength of 258.73MPa, extension rate of 9.12%.

④ AZ61 Ce rare-earth to join in, because of Al's "pinning" makes Al4Ce phase diffusion rate greatly reduced, α-Mg in the Al concentration decreases, the hardness of the AZ61 magnesium alloy peak lag, and mechanical properties compared with AZ61 decreased, but the elongation of AZ61 smaller than the decline. Degree Year: 2010