Magnesium (Mg) is strong, stiff, and lightweight, making it the most widely used element in engineered structures after iron and aluminum. Its strength and stiffness can be further improved when alloyed with aluminum.
Nevertheless, bulk mechanical properties rely greatly on chemical composition and thermomechanical history, as these factors influence microstructure. This article discusses the application of nanoindentation to measure the properties of individual phases within a commercially available alloy, AZ 61.AZ 61 Magnesium Alloy
AZ 61 contains aluminum (nominally 6%), zinc (nominally 1%), and other trace elements. Table 1 summarizes the chemical composition for AZ 61. The presence of zinc and other trace elements has little impact on the microstructure, and the phase diagram is used to deduce the composition of slowly cooled AZ 61.
At 6% aluminum, the Mg-Al phase diagram deduces the interaction of two phases: an α phase that is Mg-rich and a β phase comprising the intermetallic compound Al12Mg17.
Table 1. Chemical composition of magnesium AZ 61 alloy .
|Element||% by mass|
When the alloy cools from the liquid state, the α phase starts solidifying at about 620°C and the solidification process completes at 540°C, at which point the material exists completely in the α phase. The precipitation of the β phase begins at around 300°C and the mass fraction of this secondary phase keeps on increasing as the temperature continues to decrease. At temperatures less than 100°C, the β phase represents about 7.5% of the alloy.Instrumentation
The Keysight Express Test option is used in this analysis due to its ability to achieve unprecedented testing speeds by implementing conventional indentation testing in an innovative way. Express Test carries out one complete indentation cycle per second, which includes approach, contact detection, load, unload, and movement to the next indentation site.
Express Test can quantitatively ‘map’ the elastic modulus and the hardness of a surface in a reasonable time. This quality is especially advantageous for analyzing multiphase metals like AZ 61.
|Chemical Composition Limits|
|2.5 - 3.5||0.7 - 1.3||0.2 min||0.05 max||0.05 max||0.04 max||0.005 max||0.005 max||0.30 max total||bal|
AZ31B is a wrought magnesium alloy with good room-temperature strength and ductility combined with corrosion resistance and weldability. AZ31B finds application in wide variety of uses including aircraft fuselages, cell phone and laptop cases, speaker cones and concrete tools. AZ31B can be superformed at elevated temperatures to produce a wide variety of intricate components for automotive uses.
AZ31 is also available as tooling plate which is specially produced to provide a flat plate surface. The production process of AZ31-TP also results in plate with exceptional dimensional stability in machining. This allows for the manufacture of very complex parts but also components which benefit from the dimensional stability such as jigs, fixtures, optical benches, vibration test equipment and inspection gauges.
|Material||Condition||Thickness "||Tensile Strength||Yield Strength 0.2 %||Elongation in 4D (%)|
|Magnesium Alloy AZ31B Sheet||Cold Rolled, partially annealed||0.016 - 0.249||39||29||6|
|Magnesium Alloy AZ31B Sheet||Cold Rolled, partially annealed||0.249 - 0.374||38||26||8|
|Magnesium Alloy AZ31B Sheet||Cold Rolled, partially annealed||0.374 - 0.500||37||24||8|
|Magnesium Alloy AZ31B Sheet||Cold Rolled, partially annealed||0.500 - 1.00||36||22||8|
|Magnesium Alloy AZ31B Sheet||Cold Rolled, partially annealed||1.00 - 2.00||34||20||8|
|Magnesium Alloy AZ31B Sheet||Cold Rolled, partially annealed||2.00 - 3.00||34||18||8|
|Magnesium Alloy AZ31B |