First-principles and experiment perspectives of Hf alloying significantly strengthened TaW alloys

The room temperature strength and hardness of TaW alloys limit their further development for engineering applications. In order to improve the room temperature mechanical properties of TaW alloys, Hf elements was selected to strengthen the traditional TaW alloys. The elastic constants and charge densities of Hf-doped TaW alloys were calculated by first-principles to reveal the strengthening effect. It was found that the Hf alloying obviously enhanced the hardness of TaW alloys, which was attributed to the formation of metallic and ionic bonds in the alloys. In order to verify the calculated results, hardness and compression tests were carried out for TaWHf alloys. The hardness and yield strength significantly increased with the increased of Hf elements, which was in good agreement with the first-principles calculation. Among them, yield strength of Ta-10.17 W-19.83Hf alloy was as high as 1220 +/- 8.4 MPa, twice larger than that of the normal Ta-10 W alloy without obviously sacrifice in plasticity. It was indicated that Hf alloying can effectively strengthen TaW alloys, which provided a guidance for the development of high-performance TaW alloys.