组织细化的控制相变技术机理研究

RPC PROCESSING TO REFINE BAINITE

在Ｇｌｅｅｂｌｅ－１５００热模拟机上模拟了不同的弛豫析出控制相变(ＲＰＣ)工艺过程,结合金相、ＳＥＭ、ＴＥＭ以及ＥＢＳＤ技术研究了不同变形温度,变形量以及弛豫时间对含Ｎｂ,Ｔｉ低碳微合金钢最终组织细化的影响．此外Ｆｅ－Ｎｉ合金被用来研究弛豫过程中的位错亚结构变化以及析出行为．结果表明,经ＲＰＣ工艺处理后,贝氏体束可得到明显的细化．弛豫过程中同时存在位错弛豫、多边形化形成位错胞状亚结构以及应变诱导析出,这两者是引起最终贝氏体组织细化的主要原因．当两种因素互相协调并促进时,细化效果最佳,在本模拟条件下,最佳控制工艺为８５０℃变形后弛豫６０－２００ｓ左右．

The influence of different relaxation-precipitation-controlling transformation (RPC) processes on the microstructure refinement of low carbon bainitic steels with Nb and Ti was studied by thermo-simulation test at a Gleeble-1500 thermo-simulator. By using OM, SEM, TEM and EBSD, the microstructure, dislocation substructure and precipitation were investigated. In addition, a Fe-Ni alloy was used to understand the variation of dislocation substructure during relaxation. The results indicated that after RPC processing the bainite sheaves were refined markedly. The polygonal dislocation substructure and strain induced precipitation formed during the relaxation are two important causes for the refinement. Under the optimum processing the refinement by these two processes accelerates each other and the best processing is relaxing for 60-200 s at 850 degreesC.