The whiskers can absorb the energy of alloy crack propagation, and the magnitude of the absorbed energy is determined by the bonding state of the whiskers and the matrix. When the whiskers are pulled out from the alloy matrix under the external load, a part of the external load energy is consumed due to the interface friction, so as to achieve the purpose of toughening. The toughening effect is affected by the sliding resistance between the whiskers and the interface. There must be a lot of binding force between the whisker and the substrate interface, so that the external load can be effectively transferred to the whisker, and the binding force should not be too large to ensure a sufficient pull-out length. Crack deflection toughening: When the crack tip encounters the second phase with an elastic modulus greater than that of the matrix, the crack will deviate from the original advancing direction and expand along the interface of the two phases or within the matrix. Since the non-planar fracture of the crack has a larger fracture surface than the planar fracture, it can absorb more external energy, thereby achieving the effect of increasing the toughness.
The addition of whiskers or particles with high elastic modulus into the matrix can cause crack deflection and toughening mechanism. When the matrix is fractured, the whiskers can bear the external load and act as a bridge connection between the broken crack surfaces. The bridged whiskers can generate a force on the matrix to close the cracks and consume external loads to do work, thereby improving the toughness of the material.
