Visual Testing (VT) Practice Exam

What is the term for an inherent discontinuity formed during the original solidification of metal?

1. A seam

2. Thermal fatigue

3. A hot tear

4. Porosity

The correct answer is: Porosity

The correct term for an inherent discontinuity formed during the original solidification of metal is porosity. This occurs when gas bubbles are trapped in the metal as it solidifies, leading to voids or pores within the material. These pores can impact the integrity and mechanical properties of the final product, potentially leading to weaknesses. In casting and solidification processes, gas solubility changes, and cooling rates can contribute to the formation of porosity. It is significant in the context of visual testing because inspectors must be able to identify and evaluate the effects of porosity in materials to ensure quality and performance standards. The other choices refer to different types of discontinuities or failures. A seam typically refers to a type of defect caused by improper joining or mixing of materials. Thermal fatigue is related to the mechanical fatigue that occurs from temperature fluctuations rather than solidification issues. A hot tear is a specific defect that can happen during the solidification phase but is distinct from porosity, as it involves the cracking or tearing of the material due to thermal stress, not voids caused by trapped gas.