MICROSTRUCTURE OF CAST MgBi6X0.5 (X = Ca, Mn, Zn) ALLOYS IN PEAK-AGED CONDITION

• DOI: 10.32730/imz.2657-747.21.3.3
• Publication Date: 2022-03-22T11:44:38Z
• Authors: Adam Gryc; Bartlomiej Dybowski; Robert Jarosz; Andrzej Kielbus
• Keywords: Precipitation hardening; Mischmetal

Cast magnesium alloys are characterised by the lowest density among commercially used structural metals. They applied mainly in transportation industry and small, lightweight electronic devices. Due to low operating temperature of most widely from Mg-Al system, containing rare earth elements with maximum working reaching 300°C have been developed. However, these extremely expensive due availability RE elements. The Mg-Bi system is a promising candidate for new magnesium-based alloys, as it reveals limited solubility Bi Mg enabling precipitation hardening high melting point Mg3Bi2 phase. paper presents results analysis MgBi6 MgBi6X0.5 (X = Ca, Mn, Zn) alloys’ microstructure peak-aged condition. analysed as-cast condition consists α-Mg solid solution dendrites Mg3Bi2+α-Mg eutectic compound. Solutionising conducted at 525°C 8 h, followed water quenching leads dissolution intermetallic phases all investigated apart MgBi6Ca0.5 alloy. In this case, fine Mg, Bi, Ca found after solutionising. ageing 200°C peak hardness 120–144 h. heat treatment formation strengthening within solution, variety morphologies – needle, platelet- or lathlike cuboid. needle- two sizes large, length hundreds nanometres, smaller, not exceeding 100 nm. Cuboid particles higher than addition Mn Zn increases precipitate volume fraction treatment. Additionally, case MgBi6Zn0.5 alloy, forming an angle 120° were found, which indicates their presence prismatic planes HCP crystal lattice.