Effects of chromium addition on fracture toughness and hardness of oriented bulk Fe2B crystals

• The interplanar spacings of two oriented Fe2B have different variation trends.
• The toughness variation trends along two oriented directions are different with Cr addition.
• The hardness variation trends of two oriented sections are different with Cr addition.
• The interplanar spacing variation is the essential reason for different properties.

Effects of different chromium addition on the microstructure, fracture toughness and hardness of oriented Fe2B bulk were investigated. The results indicate that, with increasing Cr addition, the interplanar spacings of the two perpendicular crystal planes ((002) and (200)) of oriented bulk Fe2B crystals have different variation trends, and the transversal fracture toughness of oriented Fe2B bulk increases first and then decreases, while the longitudinal fracture toughness decreases gradually. The results also indicate that, with increasing Cr addition, the hardness of longitudinal section increases first and then decreases; however, the hardness of transversal section decreases gradually. Furthermore, by analyzing the variation trends of surface energies and interplanar spacings of two perpendicular crystal planes, it can be concluded that, the variation of interplanar spacing due to Cr solution should be the essential reason for different fracture toughness and hardness of oriented Fe2B crystals.