报告题目：Brazing of Ni-base Superalloy 600 using a NewlyDeveloped Multi-Principal-Component Filler Foil
报告人：Prof. Zhenzhen Yu
时间：2018年6月4日(星期一)下午3：00
地点：材料馆A323
Biography:
Prof. Zhenzhen Yu is an assistant professor in the department ofMetallurgical and Materials Engineering (MME) at Colorado School of Mines, andis affiliated with the Center for Joining, Welding and Coatings Research(CWJCR). She received MS and PhD degrees from the Department of MaterialsScience and Engineering at the University of Tennessee, Knoxville and B.S.degree from Mechanical Engineering at East China University of Science andTechnology. Before joining CSM, she worked as a postdoctoral research associateat Oak Ridge National Laboratory. Her research interests include weldmetallurgy, development of similar/dissimilar joining technologies, andsimulation and characterization of transient material state (e.g., phasetransformation, strain distribution and evolution of precipitates/voids invarious alloys) during manufacturing and processing. She serves on multiplenational committees including the Education Committee and Technical PaperCommittee in American Welding Society (AWS) and Joining Critical Technology SectorCommittee in ASM international.
Abstract:
A new multi-principal-component alloy (MPCA) fillermetal, Mn35Fe5(CoNiCu)20, was designed forbrazing of Ni-base superalloy 600 using thermodynamic calculations (including atomicsize difference, mixing entropy, mixing enthalpy, and valence electronconcentration principles) and phase diagram predictions. X-ray diffractionmeasurement confirmed that the MPCA has a face-centered cubic (FCC) structure.The MPCA exhibited a true yield strength of 286 MPa, compressive strength of591 MPa and fracture strain of 106%, and melting range of 1080-1150 ˚C. Theoptimum brazing temperature was determined to be 1200 ˚C with a wetting angleof 13.9˚ through wetting angle tests conducted over a range of temperatures.The MPCA plate was cold rolled into foils with a thickness of 300 µm forbrazing. The effect of brazing time (ranging from 15 to 120 min) on the shearstrength of the brazed joint was evaluated. A maximum shear strength of 530±20MPa was achieved with a brazing time of 90 min. With increasing brazing time,the longer interdiffusion distance facilitated a stronger metallurgical bond.However, beyond 90min, the formation of Cr-Mn rich segregations, containing amixture of brittle Cr2Mn3and CrMn3intermetallic compounds, at the grain boundaries of filler foils led to a lowershear strength and brittle fracture in the joint.
