退火温度对0Cr25Al5热轧态盘条钢组织及性能的影响

采用显微组织分析和分子动力学模拟等方法研究了退火温度对0Cr25Al5热轧态盘条钢组织及性能的影响。结果发现,晶粒尺寸随温度的升高逐渐增加并趋于稳定,但是断后伸长率和断面收缩率在950 ℃突然大幅度下降。试样组织形貌在800 ℃和950 ℃退火温度下的OM及SEM分析结果未见明显差别。于是使用分子动力学模拟对0Cr25Al5钢三元体系的自由能进行了计算,发现随着B2结构的FeAl或者DO3结构的Fe₃Al有序相尺寸的增大,系统自由能先减小后增大,其最小值随着退火温度的升高向有序相颗粒尺寸减小的方向移动。在1273 K的高温下仍然会保留60 nm左右大小的有序相颗粒。因此,推测0Cr25Al5钢在大于950 ℃的温度范围内韧性下降是由于60 nm左右的B2结构的FeAl或者DO3结构的Fe₃Al有序相造成,与晶粒尺寸无关。因此,针对该钢种应进行低温退火促使基体组织回复以消除缺陷,从而抑制Fe、Al等基体原子的扩散。

Effect of annealing temperature on microstructure and properties of hot rolled 0Cr25Al5 wire steel

Effect of annealing temperature on microstructure and properties of hot rolled 0Cr25Al5 wire steel was studied by means of microstructure analysis and molecular dynamics simulation.The results show that with the increase of temperature,the grain size is increased gradually and tends to be stable,but the percentage elongation and percentage reduction of area after fracture is decreased sharply at 950 ℃.The OM and SEM microstructure of the specimens annealed at 800 ℃ or 950 ℃ have no obvious difference.And the free energy of 0Cr25Al5 steel ternary system is calculated by molecular dynamics simulation.With the increase of ordered phase size of FeAl with B2 structure or Fe₃Al with DO3 structure,the free energy of the system is first decreased and then increased,and with the increase of annealing temperature,its minimum value is moved to the direction of the decreasing size of ordered phase particles.At the high temperature of 1273 K,the size of ordered phase particles is still remained about 60 nm.Therefore,it is speculated that the decrease toughness of 0Cr25Al5 steel in the temperature range above 950 ℃ is due to the ordered phase of FeAl with B2 structure or Fe₃Al with DO3 structure at about 60 nm,which is independent of grain size.Therefore,for the kinds of steels,to eliminate defects,a low temperature annealing shall be adopted to make the recovery of the matrix,which can inhibit from the diffusion of matrix atoms.