The metallurgical situation can be modified by various factors such as stress, time, temperature and environment. In fact, these elements can increase or decrease the resistance.
Metallurgical instabilities – The instability sources
What are the sources of metallurgical instability? There are many causes that may lead to instability, here we see some of them:
- transgranular and intergranular fractures transition
- recrystallisation
- aging and over-aging
- precipitation of phases
- decomposition of carbides, borides or nitrites.
Some other source of instability
In addition, to those already mentioned, there are also other types of sources of instability as
- precipitation of intermetallic phases
- order-disorder transition
- generalized oxidation
- intergranular corrosion
- stress corrosion.
In detail: transgranular and intergranular fracture transition
Basically, the transgranular and intergranular fracture transition occurs when the grain boundaries properties are different from those of the heart of the grain. How?
- To high temperature: grain boundaries fail (the fracture thus becomes intergranular)
- To low temperature: external grain boundaries becomes more resistant than on internal boundaries.
Each stress combination and stress life, correspond to a temperature above which the fracture becomes intergranular.
In other cases, however, a fracture can be either trans-and intergranular.
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