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和其它测试方法相比,应力松弛试验是研究析出过程的最好方法。用力学方法研究冶金现象是当今流行的方法,二者的结合将有利于优化冶金过程并加深对物理现象的理解。用应为松弛方法研究低碳贝氏体钢的析出过程,就是一个实例。文中选用含Mn、Nb和B的低碳贝氏体钢为试验材料,试验温度范围为800～950℃。试件经固溶处理,固溶温度为1250℃,松弛前施加20％的预应变,应变速率为10~(-1)/s。试验结果用Stress Vs.Log(time)曲线表示,但与一般应力松弛曲线不同。当有析出物出现时,应力松弛曲线上出现了由两个拐点形成的平台,第一个拐点(P)表明了析出过程的开始,第二个拐点(P)表明了析出过程的结束。根据不同温度下的析出开始时间与结束时间,可绘制出C状的PTT曲线。用透射电镜萃取复型技术可观察到析出物Nb(CN),证明了上述结论的正确性。
Compared with other testing methods, stress relaxation tests are the best way to study the precipitation process. The mechanistic study of metallurgy is a popular method today, and the combination of the two will help optimize the metallurgical process and deepen the understanding of physical phenomena. An example is the study of the precipitation process of low carbon bainitic steel with a relaxation method. In this paper, low carbon bainitic steels containing Mn, Nb and B are selected as the test materials, and the test temperature range is 800 ~ 950 ℃. The specimens were solution treated, the solution temperature was 1250 ℃, pre-strain was applied 20% before relaxation, and the strain rate was 10 ~ (-1) / s. The test results are represented by the Stress Vs.Log (time) curve, but different from the general stress relaxation curve. When precipitation occurs, a platform formed by two inflection points appears on the stress relaxation curve. The first inflection point (P) indicates the beginning of the precipitation process and the second inflection point (P) indicates the end of the precipitation process. According to different temperature precipitation start time and end time, can draw C-like PTT curve. The precipitation of Nb (CN) can be observed by TEM technique, which proves the correctness of the above conclusion.