Microstructure characteristics for quench sensitivity of in-situ TiB 2 /7050Al composite

The quench sensitivity (QS) related to hardness of TiB2/7050Al composite has been investigated by Jominy end quench (JEQ) test, and the underlying factors of microstructure characteristics to influence the QS of the composite were discussed. Once the JEQ experiment was completed, the hardness test was performed on aged samples to show that there was a significant decrease with the increasing distance from the quenching end. As the distance increased, more η phases were found to precipitate and coarsen on grain boundaries, Al3Zr dispersoids and dislocations. Meanwhile, the precipitation free zones became wider and the η′ phase grew larger and less dispersive. The TiB2/7050Al composite was found to be more quench sensitive than its alloy counterpart. Through the detailed analyses, the elevated QS of the composite can be ascribed to four microstructure characteristics, which have inherited from the Al matrix and originated from the TiB2 addition accordingly.