Enhancing strength-ductility properties of immiscible W-Cu composite by creating low-energy phase interfaces

The immiscible bimetallic composites play an important role in civilian industries and aerospace fields owing to their integrated mechanical and physical properties. However, metallic composites of immiscible constituents suffer from one critical drawback of weak interface bonding, which makes the composites particularly vulnerable at elevated service temperatures. Here we proposed a novel strategy to resolve the challenge by creating lowenergy phase interfaces in a typical immiscible bimetallic W-Cu composite. This was achieved by in-situ reactions of WO3 and CuO with WC, which acts in a dual function as the reducing agent for the reactions and an interface forming agent. The sintered W-WC-Cu composite possessed a significant number of low-energy WC/W and WC/Cu interfaces and exhibited a compressive strength of 609 MPa and a compressive ductility of 22.6 % at 600 degrees C, which ranks among the highest in similar composites. The characteristics of WC/W and WC/Cu interfaces and their effects on the mechanical behavior of the composite were demonstrated by the timely and atomicresolved high-temperature mechanical investigations. The introduced stable interfaces were also found to induce [1 11]BCC -> [011]FCC phase transformation of W as another mechanism of plastic deformation in addition to dislocation activities in W and Cu. This study provides a new approach to greatly enhance the mechanical properties of the immiscible metallic composites.