Tungsten alloy
Tungsten is a refractory metal, with high melting point, high density, high temperature strength and high hardness and other characteristics, is widely used in medical, aerospace, defense weapons, fusion energy and other fields. However, pure tungsten has high hardness, becomes brittle at room temperature, is difficult to process directly, and has low ductility. It is this lack of ductility at room temperature that limits the further application of tungsten in industry.
Improving the toughness of metal materials can be started from two aspects. On the one hand, it is handled during the alloy design. The most common research focus is to modify the apparent characteristics of the alloy (e.g., grain size, reinforcement phase distribution, etc.), which can passivate the crack before it spreads and leads to macroscopic failure. To solve this problem in prior art, the method of adding alloying elements is usually used to improve the machining performance. For example, the high-density tungsten alloy now widely used is made of adding nickel, iron and other elements to the tungsten matrix, but in this method, the nickel and iron in the high-density tungsten alloy cannot be completely solidly dissolved with tungsten, forming a low melting point phase, so that it cannot be applied to the field of high temperature. In order to solve this problem, the preparation of perfect crystals with intrinsic plasticity has received extensive attention. The first principles calculation shows that tungsten is inherently brittle, which seriously affects the ductility of tungsten. However, the study shows that the critical strain of shear instability and corresponding internal failure is adjusted by changing the external electrical structure of the core through alloy addition, so that dislocation nucleation is activated before the crack formation, so that the material exhibits intrinsic plasticity at the macro level. Therefore, we hope that tungsten can be added to alloyed elements in the alloy design stage, and through solid solution, the alloy has intrinsic plasticity, and improve the plasticity and toughness of tungsten alloy.
