Mechanical properties of magnesium alloy AZ91 at elevated temperatures

Purpose: Purpose of this article is to extend a complex evaluation of magnesium alloys which requires very often knowledge of elastic-plastic properties at elevated temperatures. These properties are connected with microstructure that is influenced by metallurgical and technological factors and conditions of exploitation. Design/methodology/approach: Methodology Testing of magnesium alloys was based on tensile test in dependence on temperature. The methods of the light microscopy and SEM for metallographic and fracture analyses of alloys after testing were used. Findings: Objective of this work consisted in determination of changes of elastic-plastic properties of magnesium alloy AZ91 in dependence on temperature, including investigation of fracture characteristics. It was confirmed that during heating at chosen temperatures there occurs partial dissolution of minority phases. Homogenisation of microstructure is, however, accompanied by simultaneous forming of inter-granular non-integrities, which is unfavourable from the viewpoint of strength and plastic properties, especially at higher temperatures. Failure occurs practically at all temperatures basically by inter-crystalline splitting along the boundaries of original dendrites. At temperature testing near melting point of alloy the interdendrite areas melting were observed. Research limitations/implications: The experiment was limited by occurrence a void in cast alloys. Practical implications: The results may be utilized for a relation between plastic and strength properties of the investigated material in process of manufacturing. Originality/value: These results contribute to complex evaluation of properties magnesium alloys at higher temperatures namely for explanation of fracture mechanism near the melting point.