What Causes Brittle Fracture of Material?

In addition to the more common fatigue fractures, you might occasionally encounter brittle fractures. There are many causes of brittle fractures, and analyzing them can be quite challenging. However, if you understand the factors that lead to brittle fractures and consider the actual application conditions, the analysis becomes much easier. Today, we will summarize some possible causes for your reference. If you encounter other failure causes, feel free to leave a comment at the bottom to discuss.

1. First of all, low temperature brittleness is an important factor. The toughness of materials decreases at low temperatures and brittle fracture is easy to occur, especially for body-centered cubic metals, such as steel. The ductile-brittle transition temperature (DBTT) is a key indicator. When the temperature is below this value, the material becomes brittle.

2. The existence of stress concentration gap or crack will lead to stress concentration and form three-dimensional stress. If it is a three-dimensional tensile stress state, it will inhibit plastic deformation and increase the risk of brittle fracture. For example, some grooves and places with large diameter difference are prone to high stress concentration and cause brittle fracture.

3. Material defects Internal defects in the material, such as cracks, inclusions, shrinkage and other defects as crack sources, will reduce the effective bearing area. The composition of the material, such as phosphorus and sulfur content in the alloy elements, will also increase brittleness.

4. Heat treatment defects such as improper heat treatment, such as the formation of temper brittleness, will lead to a decrease in material toughness and need to pay attention to high temperature temper brittleness (second type of temper brittleness) and low temperature temper brittleness (first type of temper brittleness).

The microstructure of the material after heat treatment will also have an impact. For example, coarse grains and brittle phases distributed along grain boundaries (such as network precipitation of carbides) will reduce the toughness of the material。

5.In terms of environmental factors, hydrogen embrittlement and stress corrosion caused by environmental media can lead to material embrittlement. Hydrogen atoms enter the interior of the material and gather under stress, causing cracks. Stress corrosion cracking occurs under the combined action of specific media and tensile stress, which belongs to environmental brittle fracture.

6. The loading rate affects the material's ability to withstand loads and deform, influencing its fracture mode. High-speed loading or impact loads increase the material's tendency towards brittleness. Even materials that typically exhibit ductility can fail in a brittle manner due to insufficient time for plastic deformation. An increase in loading rate is equivalent to a decrease in temperature, causing the material to enter its brittle region at higher temperatures.