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Microstructure and Mechanical Properties of a Duplex Martensite Austenitic Steel Precipitation-hardened by VC Carbide

Changsheng XIE , Jiansheng ZHAO , Peizhen SUN , and Xia LIANG (Dept.of Mech. Eng. Ⅱ , Huazhong University of Science and Technology , Wuhan , 430074 , China)(To whom correspondence should be addressed)

材料科学技术(英文)

This paper presents an investigation on the primary microstructure and mechanical properties of a martensite-austenitic duplex steel precipitation-hardened by VC carbide. The results show that the mechanical properties at room temperature are strongly dependent upon the volume fraction of austenite fA. When fA < 32 % both ultimate strength and Vield strength are decreased with increasing fA. however. whenfA>32%, with increasing the.fA. ultimate strength rises and yield strength drops down. Experimental results at elevated temperatures. show that when test temperature ≤500℃. the yield strength to modulus ratio remains unchanged, however. as the temperature rises a substantial fall in the ratio occurs. The strength values at 600 and 700℃ are increased with increasing strain rate measured by cross-head speed of testing rnachine, The law of mixtures and the contribution of strain-induced transformation from unstable austen ite to martensite to the mechanical properties are discussed.

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硝酸羟胺的热稳定性评估及热分解机理研究

刘建国 , 安振涛 , 张倩 , 杜仕国 , 姚凯 , 王金

材料导报 doi:10.11896/j.issn.1005-023X.2017.04.030

为评估氧化剂硝酸羟胺的热稳定性,使用标准液体铝皿于3 K/min、4 K/min、5 K/min加热速率下进行热分析.借助非等温DSC曲线的参数值,应用Kissinger法和Ozawa法求得热分解反应的表观活化能和指前因子,根据Zhang-Hu-Xie-Li公式、Hu-Yang-Liang-Xie公式、Hu-Zhao-Gao公式以及Zhao-Hu-Gao公式,计算硝酸羟胺的自加速分解温度和热爆炸临界温度,并对热分解机理函数进行了研究.设计了7条热分解反应路径,采用密度泛函理论B3LYP/6-311++G(d,p)方法对硝酸羟胺的热分解进行了动力学和热力学计算.计算结果表明,硝酸羟胺热分解的自加速分解温度TsADT=370.05 K,热爆炸临界温度Te0=388.68K,Tbp0=397.54 K,热分解最可几机理函数的微分形式为f(a) =17×(1-α)18/17.硝酸羟胺热分解各路径中,动力学优先支持路径Path 6、Path 5、Path 4和Path 1生成NO和NO2,其次是Path 2、Path 7和Path 3生成N2和N2O.温度在373 K以下时,Path 1'反应无法自发进行,硝酸羟胺无法进行自发的热分解.从热力学的角度来看,硝酸羟胺在370.05K以下储存是安全的.

关键词: 硝酸羟胺 , 热分析 , 热稳定性 , 热分解机理 , 密度泛函理论

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