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NCMS & SKLAMM联合学术讲座

 

国家材料服役安全科学中心(筹)--- 新金属材料国家重点实验室

联合学术讲座

NCMS & SKLAMM Seminar

 

学术报告1

题目/Title: Case study on the failure of structural components

报告人/SpeakerDr. Chang Yong Jo, Principal Researcher

报告人工作单位/Affiliation: High Temperature Materials Group,

                         Korea Institute of Materials Science (KIMS)

 

学术报告2

题目/Title: Microstructural evolution during thermal exposure in polycrystalline

          Ni-base superalloys

报告人/SpeakerDr. Baig Gyu Choi, Principal Researcher

报告人工作单位/Affiliation: High Temperature Materials Group,

                          Korea Institute of Materials Science (KIMS)

日期/Date2010 9 29 日(星期三)/September 29, 2010 (Wednesday)

时间/Time9:00-11:15 AM

联系人/Contact:冯强教授,qfeng@skl.ustb.edu.cn; 13426028193 (石倩颖)

报告地点/Location:北京科技大学主楼 353/Room 353, Main Building

 

报告摘要/Abstract

 

Case study on the failure of structural components

     The present presentation covers various kinds of structural component failures which caused helicopter crashes, train de-rail, and marine engine of LNG tanker.

     Most of aircraft component failures are directly related to the crash of the aircraft. Therefore, the components have to have high reliability as well as less manufacturing related defects such as casting, machining, design defect of stress concentration, and so on. However, whenever aircraft crash occurs, most of the failures of the incident component are related to mechanical fatigue. Usually the investigators are interested in finding fatigue evidence on the fracture surface as well as the crack initiation site, because it is easy to approach the root cause of the failure or the crash. Even though the investigators might find the fatigue evidence on the fracture surface, sometimes the fatigue evidence may not be helpful in finding the root cause or the root cause is not directly related to the manufacturing related defects. This presentation will present several cases of fatigue related failure, overhaul problem as well as pilot error.

     Steel component failures of the train crash and the marine engine failure will be presented. The failure investigation of the incident components has to be carried out not only by fracture analysis but also mechanical property degradation and microstructural studies such as phase transformation, inclusion related failure, manufacturing process related defects and so on. Therefore, the failure investigation has to be carried out by comprehensive metallurgical approaches.

 

Microstructural evolution during thermal exposure in polycrystalline Ni-base superalloys

     The buckets in current advanced gas turbines are exposed to extremely high temperature and stress which induce significant degradation in microstructure. Though thousands of gas turbines are in service in the power generation industry, a few data on the stability of microstructure and mechanical properties of the blade alloys have been found. Therefore, microstructural evolution during thermal exposure and its effects on mechanical properties of three Ni-base superalloys have been investigated in the present study.

     After standard heat treatment, cast specimens of GTD111, IN738LC and CM247LC were thermally exposed at 871, 927and 982up to 10000 hours. The microstructural evolution during thermal exposure was observed by SEM, OM, and TEM. Tensile tests were conducted to study the effect of thermal exposure on mechanical properties.

     Segregation during casting process affects on the distribution of γ near eutectic area in GTD 111 and the morphology of MC carbide in CM247LC. The primary γ coarsened and developed from cube to spherical shape during thermal exposure in GTD 111 and IN738LC. In CM247LC, rafting of γ was observed after thermal exposure. While the MC decomposition in GTD111 and IN738LC depends on temperature, the decomposition of MC in CM247LC showed different behaviors with its morphology and position at which the carbide formed. After thermal exposure at 982, the grain boundaries of GTD 111 and IN738LC were covered with discontinuous M23C6 carbides enveloped by γ film. However, η phase formed from MC after exposure at 927and 871. While scriptal MC in CM247LC decomposed into M6C carbides, blocky MC decomposed into M23C6 carbides.

     The tensile strength of exposed specimens was lower than that of standard heat treated specimens in both GTD111 and CM247LC. The specimens exposed at 927showed slightly lower ductility at room temperature than the specimens exposed at 982because of η phase in GTD111.

 

作者简介/Speaker’s short biography

Dr. Chang Yong Jo received his BS, MS, and PhD degrees at Busan National University. He has got qualifications of Professional Engineer (PE) and Engineer in Metallurgy. He joined Korea Institute of Machinery and Materials (KIMM: KIMS; Korea Institute of Materials Science) in 1982. He was a visiting scientist in University of Cambridge from 1996 to 1998. Dr. Jo is leading High Temperature Materials study in Korea. He established the whole processing of superalloy related research at KIMS since 1982 when KIMS started to study superalloys and processing.

      Dr. Jo’s major research field is physical metallurgy, solidification phenomenon of metals and alloys, directional solidification to develop high temperature components such as directionally solidified or single crystal turbine components, relationship between microstructure and mechanical behavior of structural materials, development of new materials, phase prediction and alloy design and microstructural evolution and prediction.

      He has received 7 awards from outside KIMS and 8 awards at KIMS for his contribution in materials science and aero industries. In recent 10 years, he wrote 74 papers on the academic journal, 75 papers at International conferences, and about 100 papers at domestic conferences. He has been a committee member to Governmental organizations (Ministry of Commerce, Industries and Energy, Ministry of Science and Technology, Ministry of Government Administration and Home Affairs, Ministry of construction and Transportation, etc) such as planning of Aero industries, Korean Satellite Launch Vehicle, Future Generation Atomic Power, and electric power industry, and so on.

Dr. Baig Gyu Choi is the Principal Researcher of High Temperature Materials Group in Korea Institute of Materials Science. Dr. Choi graduated with the B.S., M.S., and Ph.D degree from KAIST (Korea Advanced Institute of Science and Technology) in 1992, 1994, and 1999, respectively. He had worked as a Postdoctoral Research Fellow of Materials Research Center in Ecole des Mines d’Albi-Carmaux in France from 1999 to 2000. He is a member of editorial committee in the Journal of the Korean Foundarymen’s Society. He has authored or co-authored over 30 papers in referred journals and conference proceedings. His research interests are alloy development, microstructural evolution, and mechanical properties of superalloys.