含硅镍低密度钢的温拉伸力学行为及强韧机制

Tensile mechanical behavior and strengthening-toughening mechanism of silicon-nickel low density steel

为了分析硅镍合金化奥氏体基低密度钢在中温环境下的拉伸变形行为,采用Instron电子拉力试验机对Fe-28.64Mn-8.99Al-1.68Si-1.39Ni-1.0C(Mn29Al9Si2Ni,质量分数/%)低密度钢在23~300℃下进行了温拉伸试验,研究了该钢的温拉伸力学行为,并采用SEM、TEM和热力学计算对该钢的强韧化机制进行了研究。结果表明,随着应变的增加,温拉伸应力-应变曲线主要包括弹性变形、均匀塑性变形和断裂等几个过程,没有明显的屈服现象。随着温度的提高,该钢的强度逐渐降低,塑性(断后伸长率)先增加后减小再升高,于200℃时出现塑性低谷,此时该钢的应力-应变曲线和应变硬化率曲线均具有明显的锯齿状特征,应变硬化率随应变的增加变化不大。而该钢在其他温度下的应力-应变曲线和应变硬化率曲线没有发现明显的“锯齿状”特征,应变硬化率随应变的增加而平缓下降。试验钢在23~300℃下的主要强韧化机制为κ-碳化物强化、应变强化、孪生诱发塑性和动态应变时效强化。较低温度下位错可动性较差对孪生诱发的促进作用、镍元素和硅元素对孪生的抑制作用、较高温度下孪生现象的减弱和温度对动态应变时效的促进或抑制作用等使得试验钢在23、100和300℃时存在明显的孪生诱发塑性,而在200℃时存在明显的动态应变时效强化的主要原因。动态应变时效强化是该钢在200℃时出现塑性低谷的主要原因。

In order to analyze the tensile deformation behavior of silicon-nickel alloyed austenite base low density steel at medium temperature,instron electronic tensile testing machine was used to analyze the tensile deformation behavior of Fe-28.64 Mn-8.99 Al-1.68 Si-1.39 Ni-1.0 C(Mn29 Al9 Si2 Ni).The mechanical behavior of the low-density steel was studied by temperature tensile tests at 23-300 ℃.The strengthening and toughening mechanism of the steel was studied by SEM,TEM and thermodynamic calculation.The results showed that with the increase of strain,the stress-strain curve of warm tension mainly included several processes,such as elastic deformation,uniform plastic deformation and fracture,and there was no obvious yield phenomenon.With the increase of temperature,the strength of the steel decreases gradually,and the plasticity(elongation to fracture)increases first and then decreases and then increases.At 200 ℃,the plastic trough appears.At this time,the stress-strain curve and the strain hardening rate curve of the steel have obvious sawtooth characteristics,and the strain hardening rate has little change with the increase of strain.However,the zigzag characteristics of stress-strain curve and strain hardening rate curve at other temperatures are not obvious,and the strain hardening rate decreases gently with the increase of strain.The main strengthening and toughening mechanisms of the steel at 23-300 ℃ are κ-carbide strengthening,strain strengthening,twin-induced plasticity and dynamic strain aging strengthening.Low temperature dislocation mobility is poor for the promotion of twinning induced effect,Ni elements and Si elements twin inhibition,temperature increase twin inhibitory effect and temperature variations and promoting or inhibitory effect on dynamic strain aging is the steel in 23,100 and 300 ℃ obvious twinning induced plasticity and obvious dynamic strain aging under 200 ℃.The main cause of reinforcement.Dynamic strain aging strengthening is the main reason for the plastic trough of the steel at 200 ℃.