Effects of thermomechanical processing on tensile and long-time creep behavior of Nb-1%Zr-0.1%C sheet

Effects of thermomechanical processing on the mechanical properties of Nb-1 wt%Zr-0.1wt.%C, a candidate alloy for use in advanced space power systems, were investigated. Sheet bars were cold rolled into 1-mm thick sheets following single, double, or triple extrusion operations at 1,900 K. All the creep and tensile specimens were given a two-step heat treatment of 1 hr at 1,755 K + 2 hr at 1,475 K prior to testing. Tensile properties were determined at 300 as well as at 1,350 K. Microhardness measurements were made on cold rolled, heat treated, and crept samples. Creep tests were carried out at 1,350 K and 34.5 MPa for times of about 10,000 to 19,000 hr. The results show that the number of extrusions had some effects on both the microhardness and tensile properties. However, the long-time creep behavior of the samples were comparable, and all were found to have adequate properties to meet the design requirements of advanced power system regardless of thermomechanical history. The results are discussed in correlation with processing and microstructure, and further compared to the results obtained from the testing of Nb-1wt.%Zr and Nb-1wt.%Zr-0.06wt.%C alloys.