Sintering and Related Powder Processing Science and Technologies: Modelling and Processing-related Topics
Sponsored by: ACerS Basic Science Division, TMS Powder Materials Committee
Program Organizers: Wolfgang Rheinheimer, University of Stuttgart; Ricardo Castro, University of California, Davis; Zachary Cordero, Rice University; Eugene Olevsky, San Diego State University

Monday 2:00 PM
November 2, 2020
Room: Virtual Meeting Room 22
Location: MS&T Virtual

Session Chair: Amanda Krause, University of Florida


2:00 PM  
Coarsening of Several Ceramic Particle Systems: Daniel Delia1; William Carty1; Hyojin Lee1; 1Alfred University
    The driving force for sintering and densification is the exchange of solid-vapor surface energy for solid-solid surface energy. Therefore, the solid-vapor surface energy must be related to the amount of measurable surface area, which may be measured by nitrogen adsorption (i.e., B.E.T. method). The potential to promote sintering of different powders should then be related to the reduction in surface energy resulting from the exchange of solid-vapor surface energy for solid-solid surface energy. It is proposed that it may be possible to identify a critical surface area necessary to promote sintering for a given powder chemistry based on the ratio of SV:SS surface energy, with respect to time, temperature, and initial surface area. Results suggest a majority of the powders (i.e., Al2O3, Y2O3, and CaO) evaluated displayed a linear reduction in surface area with increasing temperature, while CeO2 exhibited non-linear behavior proposed to be polymorphism at elevated temperatures.

2:20 PM  
Novel Low-temperature Copper Sintering Paste for Large-area Die Attachment at 200 ℃ in Nitrogen Atmosphere: Hao Zhang1; Takanori Kobatake1; Yasuyuki Akai1; Minoru Ueshima1; Katsuaki Suganuma1; 1Daicel Corporation
    In this study, we developed a new solvent and a modified sintering process which can generate reducing agent when heated for Cu sinter joining. With the help of its self-reduction ability, the prepared Cu paste could inhibit oxidation of Cu submicron particles and maintain stability at room temperature. It could realize Cu-Cu joints at 200 ℃ in nitrogen atmosphere within 30 min, and the shear strength is about 30MPa. Moreover, the sintered body of Cu paste shows a rather excellent microstructure with perfectly-maintained 3D shape and rarely-seen cracks. These results indicate that our novel Cu sintering paste has the ability to be used in the high-performance and high-reliability WBG applications, especially for the emergent requirement of large-area die attachment.

2:40 PM  
The Effect of Cryogenic Milling and Parameters of Spark Plasma Sintering on Microstructure, Phase Composition and Mechanical Properties of Metastable Beta Titanium Alloy Ti-15Mo: Anna Veverkova1; Jiří Kozlík1; Kristína Bartha1; Cinthia Correa1; Tomáš Chráska2; Josef Stráský1; 1Charles University; 2Czech Academy of Sciences
     Powder metallurgy is an alternative approach of materials preparation. One of its advantages in titanium alloys is a reduction of costs by near net shape processing. Ball milling is able to reduce grain size of powder particles while spark plasma sintering is a suitable method of compaction due to short times and low temperatures sufficient for material compaction which help to preserve achieved refinement.In this work, a powder of metastable beta titanium alloy Ti-15Mo was cryogenically milled and both initial and milled powder were spark plasma sintered in temperature range 750°C - 850°C for 1 minute to 3 minutes. The effects of milling and sintering parameters on the resulting microstructure and phase composition were studied using SEM and XRD. Microhardness and tensile/compressive tests were performed in order to characterize the mechanical properties. The cryogenic milling causes a decrease of temperature sufficient for material compaction.