Visual Testing (VT) Practice Exam

What type of discontinuity may result from environmental exposure during the service of a metal?

1. Thermal fatigue

2. Corrosion

3. Embrittlement

4. Creep

The correct answer is: Embrittlement

The correct answer, embrittlement, refers to a process that can occur when a metal is exposed to certain environmental conditions over time, leading to a loss of ductility and an increase in brittleness. This change can happen, for instance, when metals interact with specific elements, chemicals, or conditions within their environment, such as exposure to hydrogen in certain steel types. The result is that the material becomes more prone to cracking or failure under stress, without significant deformation, making it critical to consider during the assessment of a metal's performance in service. Thermal fatigue, on the other hand, involves the failure of materials due to repeated cycles of heating and cooling, which can cause cracks to form over time. Corrosion refers specifically to the deterioration of metals due to chemical reactions with their environment and while it's closely related to embrittlement, it’s a different mechanism primarily focused on material loss rather than an alteration in material properties. Creep is the gradual deformation of materials over time under constant stress and is mainly a consideration at elevated temperatures, rather than a direct result of environmental exposure that specifically leads to brittleness.