2017 | AFC ACCOMPLISHMENTS 169 amount of Cr20Mo3C6 decreases with temperature, and indeed different temperature dependencies are observed for the different M23C6 compounds.The origin of the significantly different mechanical properties depending on the addition of nitrogen was explained by thermodynamic calculation results, which indicate that the N-doped and N-free HT9 alloys have almost the same precipitation behaviors except for nitride precipitation and pure element solution. In the HT9 with higher N content, the FCC phases are predicted to exist below A3 line, which consist of pure Cr, Ni, and CrN.The amount of CrN phase decreases with decreasing temperature, while the Cr and Ni contents in FCC increase with decreasing temperature.These residual austenite phases should be the cause for the relatively lower strength and higher ductility found in the N-doped HT9 steel. (2)The second main achievement was the completion of mechanical tensile testing for the two HT9 steels after taking various TMP routes guided by the thermodynamics calculation. The two HT9 steel plates, heat-3 (standard) and heat-4 (N-doped), were received from LANL and rolled to 1.6 mm thick strips. Coupons were cut from the strips and heat-treated to produce as-quenched, single- tempered, and double-tempered conditions.The first treatment in the two-step tempering was made at four different temperatures (300, 400, 500, and 600°C) and followed by a 30 min long tempering at 750°C. As seen in Figure 2, the yield strength (YS) of the two HT9 steels monotonically decreases with test temperature, regardless of different alloy compositions and TMP routes. Over the whole test temperature range the high-N HT9 steel heat-4 (0.044 wt.% N) has noticeably lower strength than the low-N steel heat-3. Compared to the monotonic temperature dependence in strength, the ductility parameters show more complex behavior. Uniform ductility almost linearly decreased with test temperature, except for a few cases such as the as-quenched steels.The total elongations at room temperature and 600°C for both HT9 steels in all tempered conditions are in the ranges of 12–20% and 16–20%, respectively. In all tempering conditions a ductility minimum was measured at about 400°C, which is believed to be caused by dynamic strain aging (DSA).