Mechanical strengthening and recovery of C/C-Mo joints during thermal cycling

In order to prepare C/C-Mo joints that possess good thermal shock resistant performance between 1100 °C and room temperature, MoNiSi compounds and Ni-based solid solutions were introduced into the interlayer. The as-prepared C/C-Mo joints display good stability and reliability at high temperatures, in particular the unique strengthening and recovery phenomenon of mechanical strength during thermal cycling. After 5 thermal cycles, the joint strength increased by 28.4%, up to 59.19 MPa, showing a thermal shock strengthening phenomenon. When further increasing the cycles, the joint strength first decreases, then begins to recover. The joint strength has recovered to a peak of 52.39 MPa after 50 cycles, which is higher than the original strength. The thermal shock strengthening is ascribed to the release of the residual thermal stress caused by the formation of the microcracks (dominated by the rapid alternating temperature factor), while the recovery phenomenon is related to the filling of the defects caused by the flowing of the phases with low melting points like Ni-based solid solutions (dominated by the thermal treatment factor). This work provides a strategy to obtain the joints with good tolerance to multiple thermal cycles and excellent thermal shock resistant performance.