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。
Extrusion deformation was performed on a T8 steel with a fully pearlitic structure by equal channel angular pressing（ECAP） through a route Bc at 650 ℃.The ultra-microduplex structure was obtained in the high carbon steel after four passes ECAP,in which the sizes of ferrite grains and cementite particles were about 400 nm and 150 nm,respectively.The mechanical properties of the steel with ultra-microduplex structure were investigated by mini-tensile tests and the morphology of fracture surfaces was observed by scanning electron microscopy（SEM）.The results show that after four passes deformation,tensile strength of the steel with ultra micro duplex structure decreases slightly from 867 MPa to 819 MPa,but its yield strength obviously increases from 479 MPa to 664 MPa.Correspondingly,elongation and reduction of area of steel increase from 4.5%,5.2% to 18%,31%,respectively,which are markedly higher than those of the lamellar pearlite before ECAP.Hardness of the ultra-microduplex structure and the lamellar pearlite are almost at the same level.The tensile fracture of the ultra-microduplex structure is composed of many small dimples,which is typical ductile fracture,however,the fracture of original lamellar pearlite exhibits brittle cleavage fracture characteristics.
参考文献
| [1] | Valiev R Z .Structure and mechanical properties of ultrafine-grained metals[J].Materials Science and Engineering A,1997,234-236:59-66. |
| [2] | Saito Y.;Tsuji N.;Sakai T.;Utsunomiya H. .Novel ultra-high straining process for bulk materials - Development of the accumulative roll-bonding (ARB) process[J].Acta materialia,1999(2):579-583. |
| [3] | Yu. Ivanisenko;W. Lojkowski;R. Z. Valiev;H.-J. Fecht .The mechanism of formation of nanostructure and dissolution of cementite in a pearlitic steel during high pressure torsion[J].Acta materialia,2003(18):5555-5570. |
| [4] | Najafi-Zadeh A;Jonas J J;Yue S .Grain refinement by dynamic recrystallization during the simulated warm-rolling of interstitial free steels[J].Metallurgical and Materials Transactions A:Physical Metallurgy and Materials Science,1992,23(09):2607-2617. |
| [5] | Nagai K .Ultrafine-grained ferrite steel with dispersed cementite particle[J].Journal of Materials Processing Technology,2001,117(03):329-332. |
| [6] | Furuhara T;Mizoguchi T;Maki T .Ultra-fine(α+θ)duplex structure formed by cold rolling and annealing of pearlite[J].ISIJ International,2005,45(03):392-398. |
| [7] | T. Maki;T. Furuhara .MICROSTRUCTURE AND MECHANICAL PROPERTY OF ULTRA-FINE (FERRITE + CEMENTITE) DUPLEX STRUCTURE IN HIGH CARBON STEEL[J].Materials Science Forum,2003(Pt.1):19-26. |
| [8] | Maki T.Formation of(α+θ)microduplex structure and its mechanical properties in high carbon steel[A].上海,2004:519. |
| [9] | 杜忠泽,黄俊霞,符寒光,王经涛,赵西成.65Mn钢大塑性变形后的组织与力学性能[J].吉林大学学报（工学版）,2006(02):143-147. |
| [10] | Xiong Y;Sun SH;Li Y;Zhao J;Lv ZQ;Zhao DL;Zheng YZ;Fu WT .Effect of warm cross-wedge rolling on microstructure and mechanical property of high carbon steel rods[J].Materials Science & Engineering, A. Structural Materials: Properties, Misrostructure and Processing,2006(1-2):152-157. |
| [11] | 熊毅,赵文,孙淑华,吕知清,傅万堂.高碳钢中珠光体在温楔横轧过程中的组织演变[J].材料研究学报,2007(02):183-188. |
| [12] | Iwahashi Y;Wang J T;Horita Z et al.Principle of equal channel angular pressing for the processing of ultrafine-grained materias[J].Scripta Materialia,1996,35(02):143-146. |
| [13] | 陈伟,李龙飞,杨王玥,孙祖庆,张艳.过共析钢温变形过程中的组织演变Ⅱ.渗碳体的球化及Al的影响[J].金属学报,2009(02):156-160. |
| [14] | F. Wetscher;R. Stock;R. Pippan .Changes in the mechanical properties of a pearlitic steel due to large shear deformation[J].Materials Science & Engineering, A. Structural Materials: Properties, Misrostructure and Processing,2007(1/2):237-243. |
| [15] | 陈伟,李龙飞,杨王玥,孙祖庆,何建平.过共析钢温变形过程中的组织演变Ⅰ.铁素体的等轴化及Al的影响[J].金属学报,2009(02):151-155. |
| [16] | 黄俊霞,王经涛,张郑.珠光体组织的等径弯曲通道变形[J].材料研究学报,2005(02):200-206. |
| [17] | Vladimir V. Stolyarov;Y. Theodore Zhu;Igor V. Alexandrov;Terry C. Lowe;Ruslan Z. Valiev .Influence of ECAP routes on the microstructure and properties of pure Ti[J].Materials Science & Engineering, A. Structural Materials: Properties, Misrostructure and Processing,2001(1/2):59-67. |
| [18] | 林一坚,罗光敏,史海生,章靖国.一种具有优化组织和优异性能的超高碳钢[J].钢铁,2005(11):57-61. |
| [19] | Ming-Chun Zhao;Toshihiro Hanamura;Hai Qiu .Dependence of Strength and Strength-Elongation Balance on the Volume Fraction of Cementite Particles in Ultrafine Grained Ferrite/Cementite Steels[J].Scripta materialia,2006(7):1385-1389. |
| [20] | R. Song;D. Ponge;D. Raabe .Improvement of the Work Hardening Rate of Ultrafine Grained Steels Through Second Phase Particles[J].Scripta materialia,2005(11):1075-1080. |
| [21] | R. Song;D. Ponge;D. Raabe .Mechanical properties of an ultrafine grained C-Mn steel processed by warm deformation and annealing[J].Acta materialia,2005(18):4881-4892. |
| [22] | 林慧国;傅代直.钢的奥氏体转变曲线-原理、测试与应用[M].北京:冶金工业出版社,1988 |
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