The quantitative assessment of the fracture profile of magnesium alloy qe22 welded joint

Magnesium alloys are a part of a group of lightweight and ultra-lightweight alloys, which are important in practical use in constructions. QE22 casting magnesium alloy containing silver, rare earth elements and zirconium is characterized by creep resistance up to the temperature of 200 °C, while during a short exposure it can resist up to the temperature of 250°C. Nowadays, QE22 magnesium alloy are used for casting into sand moulds. In castings of magnesium alloys defects or inconsistencies (such as casting misruns, porosities and cracks) often appear, particularly in huge dimensional castings. Such defects are repaired with the use of padding and welding. Welded joints must ensure suitable operational properties, mainly in terms of creep, so that the repaired casting can work under the same conditions as the correct cast. The basic source of information about the cause and cracking propagation is fracture after creep test. The quantitative fractography, in particular profilomety, allows to describe the fracture and basis on it conclude the causes of destruction. In this paper quantitative procedure for assessing the fracture profile of QE22 welded joints after creep test was worked out. Base on its analysis result, it was found that creep resistant of the QE22 joints is determined by eutectic areas, therefore they must be heat treated after welding joints.