AZ91C-T4 & AZ91D
These are the most commonly used Magnesium Alloys across industries. Two of the most similar Magnesium alloys, in their composition and physical properties are AZ91C – T4 and AZ91D. The composition of Aluminum is almost the maximum when compared to other alloys ranging from 8-9 percent. The major distinguishing factor between these two alloys is their process of formation. AZ91C – T4 is obtained by the process of Sand Casting and AZ91D by Die Casting. The fact that their melting points are lowest (AZ91D) and second lowest (AZ91C – T4) respectively among all the other alloys, makes them easily obtainable from Casting, which essentially requires decent melting points. A striking difference lies in the yield strength of the two, where AZ91D has almost double the yield strength than AZ91C – T4. The easy accessibility and feasibility of the two alloys makes them the most used Magnesium alloys globally. Both these alloys generally exhibit the normal characteristics expected of an alloy, but AZ91D is especially beneficial in areas where maximum resistance to corrosion is required, which is to say it doesn’t rust or degrade over a good period of time, even with little care of the material.
AM50 ranks among the lightest of Magnesium alloys owing to its low density of 1.77 g/cm3. The process employed to cast AM50 is called Die Casting. This alloy can also be efficiently drawn into wires due to its high ductility, with a tensile strength of 200 MPa (Mega Pascals), though it isn’t very ideal to be beaten into sheets given its low sheer strength (better only than AZ80A-T5 (Forged). Like most alloys the major composition consists of Magnesium and Aluminium, the latter constituting only a very small fraction when compared to other alloys. The alloy is extensively used in Automobile and Aerospace industry in parts like steering wheels and instrument panels, due to its lightweight ability and heat absorbing characteristics.
There isn’t a stark difference between characteristic properties of AM60A and AM50A. The density for this alloy is slightly more, 1.8g/cm3, though the conductivity (both electric and thermal) are less by a small amount. This alloy is also used in die casting process. Due to its tensile properties and tough nature with reasonable yield is extensively used in Automobile wheels. It has slightly greater molecular strength and hence a higher melting point that AZ91 alloys. It is advisable to use this alloy in parts that have least exposure to salty water, as this alloy doesn’t possess great resistance to corrosion. However, corrosion resistent coating have advanced significantly over the years to help overcome this challenge.
ZE41 – T5
ZE41 – T5 has the maximum density of 1.84 g/cm3. The composition of this alloy differs from the others as the amount of Zinc present is quite significant. It stands out among other alloys on the criteria of electric conductivity with 39% IACS. The number preceding International Annealed Copper Standard in percentage gives the relative conductivity in comparison to Copper, which is considered to be 100% conductive. The alloy proves useful in high integrity casting operations that function at an ambient temperature with an upper limit of almost 150°C. It’s coefficient of thermal expansion is the most among all the other alloys, indicating that it would expand linearly the most in comparison. This versatile alloy is used in many diverse fields such as, aerospace, automotive, military and electronic applications for example, castings in ZE41 are found in helicopter gearboxes, performance car components, video cameras, military equipment, vibration testing equipment etc. Interestingly, there are some institutions that currently are carrying research on the poor corrosion resistance of this alloy.
AZ31B - H24
One among the least dense alloys, its composition mainly consists of Magnesium with just 3% of Aluminum involved. The electric conductivity though is decent but almost half that of ZE41 – T5, which has the best conductor. AZ31B – H24 does not show any magnetic properties but has high electrical and thermal conductivity making it of great use in Resonance Field Imaging (RFI) and Electromagnetic Shielding, as the currents fail to induce magnetic behavior, serving the desired purpose. With a shear strength of 160 MPa it gets beaten into sheets quite easily and is used in thin sheet forms. Superplastic forming of AZ31B sheet at elevated temperatures allows production of a wide variety of intricate parts for automotive uses. AZ31B is a wrought magnesium base alloy with good room-temperature strength and ductility combined with corrosion resistance and weldability. The strength of the alloy can be increased fairly by strain hardening with subsequent partial anneal (H24 and H26 tempers.) Magnesium AZ31B-H24 provides much better strength to weight ratio when compared to Aluminum and Zinc alloys.
AZ80A – T5 (Extrusion) and AZ80A – T5 (Forged)
Both of these alloys are similar to each other in many ways, particularly in physical properties like density (1.8 g/cm3), melting point (610°C), thermal conductivity etc. The major differences arise on the strength front as Extrusion alloy has greater tensile, shear and yield strength than its Forged counterpart. The compositions of the two remains unchanged despite of different generation processes. Owing to its higher strength capacities the extruded alloy is used in areas where higher fatigue strength is required. The forged alloy has a fine controlled microstructure has the process itself eliminates surface porosity & internal cavities and voids. Forgings in AZ80A find application in high strength parts for satellites, helicopter gearboxes and rotor hubs, bicycle frames, road wheels, missile frames and inter stage fairings, brake housings and landing gear struts. The forgings of AZ80A could be used where pressure tightness or high machinability is required since it requires little power to cut them and they deliver satisfactory finish afterwards.