Solid State Diffusion Bonding of Metals and Alloys: Solid State Diffusion Bonding of Metals and Alloys I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Mohamed Elbakhshwan, University of Wisconsin Madison; Mark Anderson, University of Wisconsin Madison; Todd Allen, University of Michigan ; Tasnim Hassan, North Carolina State University
Monday 8:00 AM
February 24, 2020
Room: 19
Location: San Diego Convention Ctr
Session Chair: Mohamed Elbakhshwan, UW-Madison; Tasnim Hassan, North Carolina State University; Mark Anderson, University of Wisconsin Madison
8:00 AM Introductory Comments
8:10 AM Cancelled
Effect of Diffusion Bonding Parameters on Joint Efficiency of Fe- and Ni-base Alloys: Sung Hwan Kim1; Ji-Hwan Cha1; Changheui Jang1; 1Korea Advanced Institute of Science & Technology
Diffusion bonding is a key technology for fabrication of compact heat exchangers such as the printed circuit heat exchanger (PCHE), which would be applied in next generation nuclear power plants. Meanwhile, appropriate selection of structural materials is necessary in consideration of specific operating conditions for each system. Thus, in this study, diffusion bonding of various Fe- and Ni-base alloys have been conducted and the effect of bonding parameters on joint efficiency have been evaluated. It was found that diffusion-bonded 300-series austenitic stainless steels had comparable tensile properties to the as-received condition. On the other hand, diffusion-bonded Ni-base alloys exhibited low tensile ductility due to premature brittle failure at the bond-line especially at elevated temperatures. Application of post-bond heat-treatments seemed to somewhat improve the elongation of these joints. Preliminary results on effect of Ni-interlayer insertion on diffusion-bond integrity of Ni-base alloy joints are also discussed.
8:40 AM
Diffusion Bonding of AgC-Cu Bi-Layered Electrical Contacts: Daudi Waryoba1; Linsea Paradis1; 1Pennsylvania State University
The conventional press and sinter method for fabrication of bi-layered silver graphite-copper electrical contacts has shown to be challenging process due to the immiscibility of graphite in copper and silver. During sintering of silver graphite-copper compacts, silver diffuses into copper leaving a trace of graphite at the interface. This creates a poor interface between the mating surfaces, thereby decreasing the shear strength of the joint. In this work, interlayers with different compositions were used to promote diffusion bonding at various sintering conditions. Microhardness, electrical resistivity, electron backscatter diffraction (EBSD), and shear testing, are some of the techniques used to characterize the microstructure of diffusion bonded parts.
9:00 AM
Diffusion Bonding of Ti-6Al-4V Alloy to Interstitial Free (IF) Steel Using Copper and Nickel Interlayers: Manil Raj1; M.J.N.V. Prasad1; K Narasimhan1; 1IIT Bombay. MEMS Dept.
In present study, Ti-6Al-4V alloy and interstitial free steel were diffusion bonded using thin layers of copper, nickel and without interlayers at three different temperatures of 750°C, 850°C and 950°C under a constant pressure of 10 MPa for holding time of 10 minutes. The influence of bonding temperature and the effect of interlayer/s on the joint interfacial microstructure and bond strength were analyzed by electron microscopy, nanoindentation and shear testing. With increasing temperature, the characteristics of interlayers change from rich barrier to complete loss of it content and resulting the interdiffusion of the base metals. This reflected in significant variation of hardness across interface with respect to bonding characteristics. The joint produced with Ni interlayer exhibited optimum shear properties at lowest bonding temperature because of sound interface with less brittle compound.
9:20 AM
Bulk-state Reaction for Synthesizing Bulk Hybrid Alloys through High-pressure Torsion: Megumi Kawasaki1; Jae-Kyung Han1; Terence Langdon2; 1Oregon State University; 2University of Southampton
Processing through the application of high-pressure torsion (HPT) provides significant grain refinement in bulk metals at room temperature. These ultrafine-grained (UFG) materials after HPT generally demonstrate exceptional mechanical properties. Recent reports demonstrated the bulk-state reactions for the synthesis of hybrid alloy systems by utilizing conventional HPT processing for direct mechanical bonding of dissimilar bulk metal disks during concurrent grain refinement. Accordingly, the present study shows processing of several UFG Al hybrid alloy systems including Al-Mg and Al-Cu by HPT under 6.0 GPa at room temperature and the experiments were conducted for examining the evolution of microstructure, mechanical properties and additional functionalities including specific strength. This study demonstrates a significant opportunity for making use of HPT for a significant contribution to current developments in diffusion bonding, welding and mechanical joining technologies as well as to introduce hybrid engineering materials.
9:40 AM Break
10:10 AM
Mechanical Characterization of Diffusion Bonded Alloy 800H: Heramb Mahajan1; Tasnim Hassan1; 1North Carolina State University
High efficiency of Compact Heat Exchangers (CHXs) lead to research and development on their fabrication processes and failure mechanisms for determining their applicability to next generation nuclear plants (NGNPs). One of the important fabrication processes of CHXs is the diffusion welding of stacked etched plates. Specified compressive stress and temperatures (beyond recrystallization) are prescribed over a specified duration for diffusion welding, which results in microstructural changes affecting material properties. Knowledge of microstructures and material properties of diffusion welded alloys at high temperatures are limited, but are essential for development of ASME design methodologies and code provisions for application of CHX to NGNPs. This study will evaluate mechanical and microstructural properties of diffusion welded Alloy 800H through a systematic set of tension, creep, fatigue and creep-fatigue tests at various temperatures. Efforts will be made to correlate microstructures to mechanical properties of Alloy 800H.
10:30 AM
Interfacial Recrystallization and Element Diffusion during the Hot Compression-bonding of Ti-6321 to TC4: Bijun Xie1; Mingyue Sun1; Bin Xu1; Dianzhong Li1; 1Institute of Metal Research, Chinese Academy of Sciences
Conventional diffusion bonding method to manufacture aircraft components of titanium alloy may result in microstructure coarsening, long manufacture cycle and increased cost due to long bonding time. To avoid the disadvantages of diffusion bonding, the hot compression bonding was employed to join dissimilar titanium alloy. The results indicate that Ti-6321 alloy and TC4 alloy could be successfully bonded without micro-voids or precipitates along the bonding interface. Using electron backscattered diffraction technique, we found that obvious dynamic recrystallization grains appeared at the bonding interface, which is caused by discontinuous dynamic recrystallization. With increasing of strain, the area of interfacial recrystallization became wider and the original bond line disappeared completely. Besides, TEM results show that Mo and Nb enrichment appeared in the beta phase of TC4 side near the bonding interface, which indicates that Mo and Nb atoms diffused from Ti-6321 side to TC4 side through special diffusion channels.