Influence of Deformation Temperature on Hot Ductility of As-cast Austenitic Stainless Steel
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摘要: 通过高温拉伸试验,研究了变形温度对铸态及热加工态奥氏体不锈钢Cr15Mn9Cu2NiN热塑性的影响。结果表明,在1 250℃时,铸态与热加工态试样的断面收缩率均在85%以上;随着变形温度的降低铸态试样的塑性迅速下降,而热加工态试样则无明显变化;变形温度降至900℃时,铸态试样的断面收缩率只有45%左右。分析认为,铸态试样中具有明显结晶取向的柱状晶,随着变形温度的降低,在变形过程中会迅速强化,使得晶粒间的变形协调能力迅速下降,导致在晶界或相界等较薄弱处产生应力集中,进而引起裂纹的形核及塑性的快速降低;而热轧板试样中为细小的等轴晶,变形协调能力强,变形时,应变会均匀地分布在每个晶粒上,使得其热塑性较高。Abstract: The influence of deformation temperature on the hot ductility of as-cast and hot-rolled austenitic stainless steel Cr15Mn9Cu2NiN is investigated via high-temperature tensile tests.Results show that at 1 250℃,reduction of areas(RA) in both as-cast and hot-rolled specimens are higher than 85%.As the deformation temperature decreases,hot ductility of as-cast specimens drops rapidly while there is no obvious variation for that of hot-rolled specimens.As the deformation temperature decreases to 900℃,RA of as-cast specimens is just around 45%.Analyses suggest that microstructures in as-cast specimens are coarse columnar grains,deformation coordination ability of which falls fast with decreasing deformation temperature,leading to strain concentration at grain boundary or phase boundary,and then resulting in crack nucleating and rapid reduction of hot ductility.For hot-rolled specimens,the microstructures are homogeneous and fine equiaxed grains with excellent ability of deformation coordination; during deformation,the strain uniformly distributes in all the grains,which brings about higher hot ductility.
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