Liquid Phase Sintering Distortion and Observations on Gravity Effects on

Materials Processing

 

Speaker:

Randall M. German

Brush Chair Professor in Materials

Director, Center for Innovative Sintered Products

The Pennsylvania State University

University Park, USA

 

Date/Time:  22 January 2001, 3:00 pm,

(Refreshments will be served after the end of the Seminar).

 

Venue:   LT 15, NTU (Level 4, North Spine, near CSE)

 

 

Abstract

 

A classic problem in liquid phase sintering is the attainment of full density without distortion.  There are many well-known systems, including WC-Co, Cu-Sn, Fe-Cu-C and W-Ni-Fe, where full density is possible without significant loss of precision due to slumping or distortion; however, all of these systems are characteristically high in solid content.

 

This presentation will introduce new experimental results for sintering densification in the two phase solid-liquid region.  Critical experiments have been performed to isolate gravity effects on pore buoyancy and grain settling, showing that gravity is very important to densification.  Surprisingly, we find distortion is larger in microgravity sintering and densification is less.  This means that envisioned microgravity manufacturing will be much harder than originally anticipated.  Altogether the Penn State team has processed 77 samples in microgravity, with thousands of equivalent samples processed on Earth. The measurements include densification, in situ video imaging, microscopy, and post sintering microstructure quantification.  The findings show that on Earth densification occurs prior to distortion, but in microgravity distortion occurs without densification.  A conceptual model based on strength evolution and capillarity and gravity has been formed to explain this behavior.

 

About the Speaker

 

Brief Introduction to Prof. R.M. German:

Education

 

     B.S. (Material Science), San Jose State University

     M.S. (Metallurgy), Ohio State University

     Ph.D. (Material Science), University of California, Davis

 

   Research and Teaching

 

     Dr. German's research and teaching efforts focus on particulate materials processing.

     Example research areas include:

 

          Powder fabrication

          Mixing and blending

          Characterization

          Compaction

          Sintering, especially Liquid Phase Sintering

          Microstructure control

 

     Example applications include:

 

          High performance magnets

          Tungsten-based composites

          Aluminum reduction cells

          High temperature jet engines

          Catalytic converters

          Solder pastes

          Diamond-intermetallic cutting tools

          High surface area capacitors

          Rapid prototyping systems

          Chemically inert filters

          Biomedical microdevices

          X-ray telescope collimators

          Ferrous automotive components

          High thermal conductivity micoelectronic packages

          Cemented carbides wear components

 

   Publications

 

     Books Authored

 

          Sintering Theory and Practice

          Powder Metallurgy Science, 2nd edition

          Liquid Phase Sintering

          Powder Injection Molding

          Particle Packing Characteristics

 

     Other Publications

 

          Published over 400 articles

          Edited 11 books

          Co-editor of the book series Reviews in Particulate Materials

          Inventor with over 10 patents

 

   Awards

 

          Fellow of ASM International

          MPIF Distinguished Service to Powder Metallurgy Award

          Engineering Award of Distinction from San Jose State University

          Distinguished Engineering Alumni Award from University of California

          Japan Institute of Metals Technical Development Award

          Kuczynski Award and Samsonov Prize of ITSS

          Penn State Engineering Society Outstanding Research Award 1995

 

 

Admission is free and all are welcome.  For enquiries, please contact Ms Ng Siu Din at Tel:  790 6090, E-mail:  assdng@ntu.edu.sg