Effect of Ti or Zr alloying on the microstructure evolution and mechanical properties of W-Cu immiscible bimetallic composite

Abstract

W-Cu immiscible bimetallic composite is an electrically and thermally conductive material with high temperature service potential. In present work, to improve its load bearing capacity, Ti and Zr were introduced to enhance the W-Cu interfacial bond strength and to achieve solid solution reinforcement. By infiltration of Cu-Ti/Zr alloy with different compositions into the W skeleton, both the strength and hardness were enhanced without sacrificing ductility. The Ti/Zr incorporation transformed the incoherent interface of W-Cu to a (W-Ti/Zr)-(Cu-Ti/Zr) semi-coherent interface. By utilizing the EDS technique, significant compositional interdiffusion between immiscible metals was revealed. Moreover, the introduction of Ti/Zr purified grain boundaries by capturing the reactive oxygen to generate TiO2 and ZrO2, which inhibited W-Ti/Zr grain growth by Zenner pinning. As the alloy content rose from 0 wt% to 5 wt%, the average grain size of the W-Ti/Zr (or W) alloy decreased from 2.14 µm to 1.40 µm. It is noteworthy that the alloying with 2.50 wt% Ti reached peak microhardness (417 HV), bending strength (1546 MPa), and ultimate tensile strength (532 MPa). However, the presence of Cu-Ti/Zr solid solution and oxide particles increased the scattering effect of electrons in the Cu matrix, leading to a falling in electrical conductivity.