Magnesium Alloys

Question 1

How does magnesium’s density compare with other structural metals?

Answer 1

-It is very low (density = 1.74gcm^-3)
-lowest of all structural metals

Question 2

What are the two types of deformation?
Differences between them?

Answer 2

1. Slip pane and twinning
2. Slip pane is deformation that is greater than atomic spacing and its orientation stays the same.
3. Twinning deformation is one that is smaller than the atomic spacing. Its orientation changes.

Question 3

How can the high temperature strength of Mg alloys be increased?

Answer 3

HTS can be increased by the use of ceramic fibres such as “SiC” to produce MMC (metal matrix composites).

Dispersion of elements throughout high temperatures is possible (aluminium)

Question 4

What is plastic deformation occurring within an alloy?

Answer 4

-Plastic deformation is the result of slip occurring in the material

-Slip is the movement of part of a crystalline structure relative to another

-deformation is permanent

-slip occurs on the same plane’s cryptographically

Question 5

What is the critical shear stress for slip systems and how can it be altered to different magnitudes?

Answer 5

-the critical shear stress is required to initiate a slip in a pure and perfect structure

-higher temperatures lower the stress value

Question 6

What is hot tearing?

Answer 6

Hot tearing is the most common casting fault that creates a crack during formation.

Question 7

Where does hot tearing occur and how?

Answer 7

Hot tearing occurs within the mushy zone due to the mismatching of shrinkage rates during the solidification process and compensation by additional liquid.