低温贝氏体转变对中碳钢韧性的影响

摘要：沉淀硬化钢中纳米富Cu相的析出，使微应变（α）发生改变，这不仅影响力学性能，也对腐蚀性能产生作用。为了探索α对腐蚀性能和力学性能的影响规律，通过XRD谱型分析，对商用钢LJ338ESR 在300～600℃不同时间时效析出富铜纳米相后的α、硬度和电荷转移电阻（Rf）进行了研究。结果表明，300～450℃时效，8h前α值随时效时间延长而升高，8h后由于析出相与基体失去共格，α随着时效时间延长而降低；硬度与α变化相似。600℃时效，α在时效2h达到峰值，这归因于共格微应变和逆变奥氏体两种相反因素的共同影响；600℃逆变奥氏体生成，使硬度变化较小。析出相与基体保持共格时，Rf和α随时效时间的变化呈良好的反比关系，即Rf随α的增大而减小。

Influence of low temperature bainite transformation on toughness of medium carbon steel

The precipitation of Cu rich nanophases in precipitation hardening steel leads to the change of microstrain (α), influencing both mechanical and corrosion properties. In order to explore the effect of α on corrosion and mechanical properties, the investigation of changes in α, hardness and charge transfer resistance (Rf) after the precipitation of Cu rich nanophases in commercial steel LJ338ESR aged at 300-600℃ for various time was performed by the XRD profile analysis. The results show that with aging at 300-450℃, the α increases with aging time less than 8h, and then α decreases with aging time due to precipitates losing coherency with the base metal, while the variation of hardness exhibits a similar trend as α. With aging at 600℃, the α peaks at 2h, which is attributed to the two opposite influences:coherent microstrain and reverted austenite. The reverted austenite forms at 600℃, making the hardness change slightly. The changing laws with aging time for the Rf and α exhibit a good polynomial correlation of inverse relationship in the coherent regime, i.e. the Rf decreases with increasing the α.