The most widely used general purpose casting is AZ91 Accordi

The most widely used general purpose casting is AZ91. According to the article in the link above, would the magnesium in the casting shown above be more or less ductile than alloy AZ91? See Table 1 The alloy in the casting above is more ductile than AZ91 O AZ91 is more ductile than the alloy in the casting above Why does the casting above seem to be dark grey, while the magnesium castings in the article are light grey? T point

Solution

Reason for dark grey colour of AZ91-

major alloying elements- Typically includes copper, silicon and magnesium.

minor alloyting elements- Includes nickel and tin.

microstructure modifying elements- Includes titanium, boron,strontium,phosphorous,beryllium and chromium

During the solidification or during phase chenge it liberates a lot of heat due to which tempreture insreases so fluidity incereases

when carbon equivalent is much high and rate of cooling is very low then we\'ll get the grey colour in this cooling rate and carbon content, cementite breaks in grephite and austenite this process is known as refatization and at this stage cast iron chenges to grey colour.