1 Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China 2 Technology Center, HBIS Handan Iron and Steel Group Co., Ltd., Handan 056015, Hebei, China 3 School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China 4 AC Construction Branch, State Grid Corporation of China, Beijing 100031, China
Microstructure evolution and mechanical properties influenced by austenitizing temperature in aluminum-alloyed TRIP-aided steel
1 Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China 2 Technology Center, HBIS Handan Iron and Steel Group Co., Ltd., Handan 056015, Hebei, China 3 School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China 4 AC Construction Branch, State Grid Corporation of China, Beijing 100031, China
ժҪ The Fe-0.21C-2.2Mn-0.49Si-1.77Al transformation induced plasticity (TRIP)-aided steel was heat treated at various austenitizing temperatures under both TRIP-aided polygonal ferrite type (TPF) and annealed martensite matrix (TAM) processes. The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis. The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite. Compared with the mechanical properties of the TPF steels, the yield strength and elongation of the TAM steels are much higher, while the tensile strength is lower than that of TPF steels. The stability of intercritical austenite is affected by the heating temperature, and thus the following phase transformation influences the mechanical properties, such as the bainite transformation and the precipitation of polygonal ferrite. Obvious dynamic bainite transformation occurs at TAM850, TAM900 and TAM950. More proportion of polygonal ferrite is found in the sample heated at 950��C. The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths. The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation. The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa��%.
Abstract��The Fe-0.21C-2.2Mn-0.49Si-1.77Al transformation induced plasticity (TRIP)-aided steel was heat treated at various austenitizing temperatures under both TRIP-aided polygonal ferrite type (TPF) and annealed martensite matrix (TAM) processes. The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis. The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite. Compared with the mechanical properties of the TPF steels, the yield strength and elongation of the TAM steels are much higher, while the tensile strength is lower than that of TPF steels. The stability of intercritical austenite is affected by the heating temperature, and thus the following phase transformation influences the mechanical properties, such as the bainite transformation and the precipitation of polygonal ferrite. Obvious dynamic bainite transformation occurs at TAM850, TAM900 and TAM950. More proportion of polygonal ferrite is found in the sample heated at 950��C. The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths. The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation. The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa��%.
Ju-hua Liang,Zheng-zhi Zhao,*,Cai-hua Zhang,Di Tang,Shu-feng Yang,Wei-ning Liu. Microstructure evolution and mechanical properties influenced by austenitizing temperature in aluminum-alloyed TRIP-aided steel[J].Journal of Iron and Steel Research International, 2017, 24(11): 1115-1124.
Ju-hua Liang,Zheng-zhi Zhao,*,Cai-hua Zhang,Di Tang,Shu-feng Yang,Wei-ning Liu. Microstructure evolution and mechanical properties influenced by austenitizing temperature in aluminum-alloyed TRIP-aided steel. , 2017, 24(11): 1115-1124.
Seo, Chang-Hyo, Kwon, Ki Hyuk, Choi, Kayoung, Kim, Kyung-Hun, Kwak, J. H., Lee, S. and Kim, Nack J..Deformation behavior of ferrite�Caustenite duplex lightweight Fe�CMn�CAl�CC steel[J]., 2012, 66(8):519-522
[2]
Han, Seung Youb, Shin, Sang Yong, Lee, Hyuk-Joong, Lee, Byeong-Joo, Lee, Sunghak, Kim, Nack J. and Kwak, Jai-Hyun.Effects of Annealing Temperature on Microstructure and Tensile Properties in Ferritic Lightweight Steels[J]., 2011, 43(3):1073-5623
[3]
Lee, Sangwon and De Cooman, Bruno C..Annealing Temperature Dependence of the Tensile Behavior of 10 pct Mn Multi-phase TWIP-TRIP Steel[J]., 2014, 45(13):6039-6052
[4]
Latypov, Marat I, Shin, Sunmi, De Cooman, Bruno C and Kim, Hyoung Seop.Micromechanical finite element analysis of strain partitioning in multiphase medium manganese TWIP+ TRIP steel[J].Acta Materialia, 2016, 108:219-228
[5]
Sugimoto, Koh-ichi, Kobayashi, Mitsuyuki, Nagasaka, Akihiko and Hashimoto, Shun-ichi.Warm stretch-formability of TRIP-aided dual-phase sheet steels[J].ISIJ international, 1995, 35(11):1407-1414
[6]
Sugimoto, Koh-ichi, Kanda, Akinobu, Kikuchi, Ryo, Hashimoto, Shun-ichi, Kashima, Takahiro.Ductility and formability of newly developed high strength low alloy TRIP-aided sheet steels with annealed martensite matrix[J].ISIJ international, 2002, 42(8):910-915
[7]
Sugimoto, Koh-ichi, Bingzhe, YU, Mukai, Yoh-ichi and IKEDA, Shushi.Microstructure and formability of aluminum bearing TRIP-aided steels with annealed martensite matrix[J].ISIJ international, 2005, 45(8):1194-1200
[8]
Sugimoto, Koh-ichi, Tsuruta, Junji and Mukai, Youichi.The Effects of Cold-rolling Strain on Microstructure and Formability of Al Bearing TRIP-aided Cold-rolled Steel Sheets with Annealed Bainitic Lath Structure Matrix[J].TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN, 2010, 96(1):29-35
[9]
Sugimoto, Koh-ichi, Fiji, Daiki and Yoshikawa, Nobuo.Fatigue strength of newly developed high-strength low alloy TRIP-aided steels with good hardenability[J].Procedia Engineering, 2010, 2(1):359-362
[10]
Tanino, Hikaru, Horita, Masaomi and Sugimoto, Koh-Ichi.Impact Toughness of 0.2 Pct C-1.5 Pct Si-(1.5 to 5) Pct Mn Transformation-Induced Plasticity-Aided Steels with an Annealed Martensite Matrix[J].Metallurgical and Materials Transactions A, 2016, 47(5):2073-2080
[11]
Sugimoto, Koh-ichi, Tanino, Hikaru and Kobayashi, Junya.Warm ductility of 0.2% C�C1.5% Si�C5% Mn TRIP-aided steel[J].Materials Science and Engineering: A, 2017, 688:237-243
[12]
Kobayashi, Junya, Yoshikawa, Nobuo, Murakami, Toshio and Sugimoto, Koh-ichi.Effects of Cr and Mo on retained austenite characteristics and tensile properties of TRIP-aided annealed martensitic steel[J].TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN, 2012, 98(11):610-617
[13]
Hojo, T, Kobayashi, J and Sugimoto, K.Impact properties of low-alloy transformation-induced plasticity-steels with different matrix[J].Materials Science and Technology, 2016, 32(10):1035-1042
[14]
Zhao, Z. Z., Liang, J. H., Zhao, A. M., Liang, J. T., Tang, D. and Gao, Y. P..Effects of the austenitizing temperature on the mechanical properties of cold-rolled medium-Mn steel system[J]., 2017, 691:51-57
[15]
Ramazani, A, Quade, H, Abbasi, M and Prahl, U.The effect of martensite banding on the mechanical properties and formability of TRIP steels[J].Materials Science and Engineering: A, 2016, 651:160-164
2017, Vol. 24 
