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demand for weight reduction and excellent crashworthiness in vehicles has driven the automotive industry to develop new manufacturing processes. Hot stamping (HS) is an innovative, non-isothermal forming process, which combines forming and quenching in one step. As the blank is quenched within the tool at a cooling rate of greater than 30 K s1, the austenitic microstructure transforms into martensite. A fully martensitic microstructure is generally desired due to very high tensile strengths of approximately 1600 MPa and Vickers hardness in excess of 480 HV.[1,2] The HS process is currently used to manufacture structural parts such as bumper beams, door intrusion beams, A- and B-pillars, roofs, and side rails.[1,3–7] Although fully martensitic hot-formed parts are often desired due to their exceptional high strength and intrusion resistance, they exhibit very low levels of ductility and strain to failure. Some structural parts, such as a B-pillar, may benefit from regions of reduced strength and greater ductility for improved energy absorption and resistance.[8–12] Such a part, with ‘‘tailored’’ mechanical properties, is referred to as a tailored ZHIQIANG ZHANG and XIAOHUI ZHAO, Associate Professors, and CONGHAO LIU and SONGFENG MENG, Postgraduates, are with the School of Material Science and Engineering, Jilin University, Changchun, China. Contact e-mail: zhaoxiaohui@jlu. edu.cn XIANGJI LI, Associate Professor, is with the Roll Forging Research Institute, Jilin University, Changchun, China. Manuscript submitted October 12, 2015. Article published online January 22, 2016. 824—VOLUME 47B, APRIL 2016

hot-formed part. Bardelcik et al.[13] have examined the strength of Usibor 1500P subjected to various cooling rates. The results showed that cooling rate below 30 K s1 resulted in desirable mechanical properties that may be suitable for improving the crash performance. Increasing the tool temperatures which is referred as the ‘‘in-die heating technique’’ is the effective method to produce the tailored hot-formed parts. Svec and Merklein[14] have performed studies with heated die temperatures of up to 773 K (500 °C) and have achieved hardness levels of 240 HV in the heated region and 420 HV in the cooled region. Feuser et al.[15] have performed experiments with a full-sized B-pillar with two individual heating zones up to 823 K (550 °C) and one cooling zone, with quench duration of 15 seconds. The results showed that the Vickers hardness values were found to be ranging from 250 to 270 HV with a 773 K (500 °C) tool and showed a decrease in tensile strength of approximately 50 pct. Banik et al.[16] have produced a tailored part with a hardness of approximately 200 HV in the tailored region and 425 HV in the hardened region with no indication of the heated die temperature. George et al.[17,18] used the ‘‘in-die heating technique’’ to produce regions of tailored properties within a lab-scale B-pillar. The Vickers hardness of the B-pillar region within the 673 K (400 °C) die segment varied from 244 to 260 HV, while that of the