light alloys

Question 1

Magnesium Metal is alloyed with and what happens

Answer 1

Most commonly reinforced with SiC
➢Improved yield strength, UTS, hardness, ductility
and wear resistance
➢Addition of TiC improves yield strength, tensile
strength and elastic modulus
➢Reduce the ductility during forming
➢Addition of Al2O3
reinforcement (addition)
improves the creep resistance and compressive
strength

Question 2

what is slip when talking about mg alloys

Answer 2

plastic deformation is the result of slip occurring in the metal
➢ Slip is the movement of one part of the crystal relative to another
➢ Slip always occurs on the same crystallographic planes

Question 3

mg structure and slip plane?

Answer 3

HCP and slip plane is the basal slip plane

Question 4

when does twinning occur

Answer 4

➢Twinning occurs when there is limited present slip
systems
➢Typically forms at low temperatures and high
loading rates (shock loading)
➢Describes a small number of plastic deformations
compare

Question 5

differnce between twinning and slip

Answer 5

slip-
orientation of atoms remains the same
displacement takes place in exact atomic spacing
twinning-
reorientation of atomic direction across twin plane
displacement is less than interatomic spacing.

Question 6

Mg - Al alloys have which alloying elements and what do they do

Answer 6

zinc-
results in higher tensile strength
manganese results in improvement of corrosion resistance
Al results in improved cast-ability.

Question 7

mushy zone

Answer 7

when alpha and L are present
where hot tearing occcurs mostly

Question 8

how does hot tearing occur

Answer 8

due to inadequate feeding by liquid of the volumes created by skrinkage during solidification

Question 9

extraction of titanium

Answer 9

Kroll process
2𝑀𝑔 + 𝑇𝑖𝐶𝑙4 → 2𝑀𝑔𝐶𝑙2 + 𝑇i

Question 10

properties from titanium

Answer 10

High strength to weight ratio,
➢ Low density,
➢ High corrosion resistance,
➢ Biocompatible (non-toxic and it is not
rejected by the body),

Question 11

Ti structure

Answer 11

changes from hcp to bcc by inrcease of temprature to 882 degrees

Question 12

stabilizers for alpha faze s

Answer 12

substitutional elements such as
Al,Sn,Ga,Ge
with al being main

Question 13

solid solution strengthening

Answer 13

interstitial and substitutional

Question 14

main beta stabliser

Answer 14

The main
elements are vanadium (V) and
molybdenum (Mo).

Question 15

how to create titanium alpha dash structure

Answer 15

cold water quenching-
hold at 1066 for hr then quenched
’consists of, small individual platelets
structure. It does not develop the high
strengths of Fe – C martensites since
interstitial elements are more soluble in
the low temperature  (hexagonal close
packed) phase, than they are in the 
phase.

Question 16

what stabilizers are used for a Ti aplha and beta alloy.

Answer 16

➢Aluminium (Al) is added to the alloy as α-phase stabilizer and hardener due its solid
solution strengthening effect. Vanadium (V) stabilizes ductile β-phase, providing hot
workability of the alloy.
also the alpha and beta alloys are heat treatable, high Ts, fatigue strength, low ductility and creep resistance up to 425 degrees.

Question 17

heat treatment air cooling 1066 degrees for titanium alloys

Answer 17

Intermediate cooling rate produces “acicular”
(basket weave)  phase
Fatigue cracks may nucleate relatively easily in this
structure, however there is a tortuous path for them
to follow if they are to subsequently grow.
➢ Results in generally good fatigue, and fracture
toughness, properties.

Question 18

thrid heat treatment for titanium alloys
what does it give in result

Answer 18

furnace cooling from 1066
This is close to equilibrium conditions
and the resulting microstructure is a
coarse plate-like alpha phase and retained,
intergranular beta.