MATERIAL PROPERTIES OF NEWLY DEVELOPED HEAT RESISTANT TITANIUM ALLOY 'Ti-1Cu-1Sn-0.35Si-0.2Nb' FOR AUTOMOTIVE EXHAUST APPLICATIONS

摘要

To respond to increasing demand for the use of light weight titanium alloys at high temperature in the automotive exhaust systems, a new alloy 'Ti-1Cu-1Sn-0.35Si-0.2Nb (10CSSN)" has been developed with emphasis on high-temperature strength, which should be higher than that in previously developed Ti-1Cu-0.5Nb. The new alloy was designed to utilize solid solution strengthening of Si and Sn in addition to Cu, and to utilize advantageous effects of Si and Nb against high-temperature oxidation. Major mechanical properties of 0.9-1.15mm thick 10CSSN sheets are as follows : Yield stress at 700°C is approximately 1.5 times higher than Ti-1Cu-0.5Nb, while room-temperature elongation, one of the indexes for formability, is approximately 30%, equivalent to Ti-1Cu-0.5Nb. Time required for 3% creep strain at 650°C is considerably high compared to Ti-1Cu-0.5Nb. Oxidation resistance is equivalent to or higher than Ti-1Cu-0.5Nb at 600-800°C, and high-temperature salt damage is greatly improved.