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在650℃采用等通道角挤压变形(ECAP)方法对原始组织为层片状珠光体的T8钢进行了Bc方式(每道次挤压后,试样按同一方向旋转90°进行下一道次挤压)的4道次变形,获得了晶粒尺寸在亚微米量级的超微细复相(α+θ)组织,其中等轴铁素体晶粒尺寸约为400 nm,球化完全的渗碳体颗粒粒径约为150 nm。微拉伸实验和SEM断口观察表明,经过4道次ECAP变形后,超微细复相组织的抗拉强度相对于原始珠光体组织而言有所下降,从867 MPa降至819 MPa,但屈服强度显著提高,由479MPa增加到664 MPa,相应的整体伸长率和断面收缩率分别从4.5%、5.2%增加到18%、31%,硬度值变化不明显;超微细复相组织的断口形貌由大量细小的韧窝构成,为典型的韧性断裂,而原始珠光体组织断口形貌则由河流花样组成,呈脆性解理断裂特征。
The Tc steel with lamellar pearlite in the original structure was subjected to the Bc method at 650 ° C using the Equal Channel Angular Pressing (ECAP) method (after each extrusion, the specimens were rotated 90 ° in the same direction for the next pass Extrusion), the ultrafine multiphase (α + θ) structure with the grain size of submicrometer was obtained, in which the equiaxed ferrite grain size was about 400 nm, Carbon particles have a particle size of about 150 nm. The microtensile and SEM fracture observations showed that the tensile strength of the ultrafine composite phase decreased from 867 MPa to 819 MPa after 4 passes of ECAP deformation, but the yield strength Significantly increased, from 479MPa to 664 MPa, the corresponding overall elongation and reduction of area from 4.5%, 5.2% to 18%, 31%, the hardness value of the change was not obvious; fracture morphology of ultrafine composite phase It consists of a large number of tiny dimples, which are typical ductile faults. The original pearlite fracture morphology is composed of river patterns and is characterized by brittle cleavage fracture.