A TEM study has been made on the microstructure of hard phase and matrix steel insteel-bonded carbide TiC-50 Nb.The results show that the submicrostructures of the materi-al are different for different tempering temperatures. The macro-mechanical properties areaffected mainly by the microstructure of the matrix,The secondary hardening is mainly in-duced by the precipitatiion of alloy carbides inside martensite during tempering at 560 ℃。Owing to the resolving and reprecipitating of the TiC particles in the ...