学 术 报 告
讲座主题：Formation of Intercritical Heat-affected Zone (ICHAZ) in Grade 91 Cr-Mo Steel Weldment（P91铬钼钢焊接接头的临界热影响区之形成）
报告人：厉雷钧教授，加拿大阿尔伯塔大学化工与材料工程系/加拿大国家焊接中心
时间：2016年12月21日（周三）上午9:00
地点：冶金学馆301
摘要：The softened microstructure in heat-affected zone (HAZ) is believed to contribute to the highly localized creep deformation for Type IV cracking in Cr-Mo steel weldments. However, it is not clear where this soft zone is relative to various HAZ regions, and how does the soft zone form. In this work, the soft zone is identified in intercritical heat-affected zone (ICHAZ) of the as-welded Grade 91 pipe steel weldment by microhardness mapping. The soft zone has a mixed structure of fine new prior austenite grains (PAGs) and fine retained tempered martensite from the base metal. Presence of those further-tempered martensite, originated from the base metal after the welding thermal cycles, is directly responsible for the hardness reduction in the soft zone. The softened grains are identified as recrystallized or substructured by EBSD grain average misorentation (GAM) evaluation. Identified soft zone has the highest number density of tempered martensite (42565 /mm2). The limited peak temperature and soaking time of the welding thermal cycles in the ICHAZ lead to the insufficient austenitic transformation and the existence of RTMs. Martensitic transformation within those new PAGs is restricted due to the lowered driving force from the fine PAG sizes and undissolved M23C6 carbides. The fresh martensite from new PAGs contains lower Cr (9.02 wt. %) and Mo (0.88 wt. %) concentrations than Cr (10.89 wt. %) and Mo (1.51 wt. %) of the RTMs, due to the Cr and Mo consumption of undissolved (Cr, Mo)23C6 carbides in the new PAGs.
报告人简介：
厉雷钧教授分别于华中工学院、西安交通大学及伦斯利尔工学院（Rensselaer Polytechnic Institute）取得学士、硕士及博士学位。长期致力于焊接冶金领域前沿技术研究，在钢铁及合金焊接过程中非平衡相变、组织结构及力学性能研究方向取得了一些得到认可的研究成果。鉴于其对焊接冶金领域的杰出贡献，先后被遴选为美国材料学会会士（ASM Fellow）、美国焊接学会会士（AWS Fellow）及加拿大焊接协会会士（CWA Fellow）。曾任美国材料学会（ASM International）关键焊接技术委员会(Committee on Joining Critical Technologies)主席并连续7年主持MS&T国际焊接学术会议；长期担任Metallurgical and Materials Transactions及Welding Journal编委。为重要国际组织及工业界执笔13份技术报告；于重要国际会议及世界知名大学作大会、主旨及特邀报告23次。
