Accession Number : ADA102836


Title :   Enhanced Densification of White Cast Iron Powders by Cyclic Phase Transformations under Stress.


Descriptive Note : Technical rept.,


Corporate Author : STANFORD UNIV CA DEPT OF MATERIALS SCIENCE AND ENGINEERING


Personal Author(s) : Ruano,Oscar A ; Wadsworth,Jeffery ; Sherby,Oleg D


Full Text : http://www.dtic.mil/dtic/tr/fulltext/u2/a102836.pdf


Report Date : Aug 1981


Pagination or Media Count : 32


Abstract : It is shown that densification of white cast iron powders under stress can be enhanced by multiple phase transformations through thermal cycling. This enhancement occurs by accelerated creep flow during phase changes (transformation superplasticity). The stress range where transformation-assisted densification can occur is shown to be between 1.7 MPa (250 psi) to 34.5 MPa (5000 psi). Below 1.7 MPa insufficient strain occurs during phase transformation to cause significant densification even after many transformation cycles. Above 34.5 MPa, densification occurs principally by normal slip creep. Transformation warm pressing of white cast iron powders leads to dense compacts at low pressure and short times. In addition, because the transformation temperature is low, the ultrafine structures existing in the original powders are retained in the densified compact. (Author)


Descriptors :   *STRESSES , *POWDERS , *IRON , *POWDER METALLURGY , PLASTIC DEFORMATION , STRESS STRAIN RELATIONS , DENSITY , MICROSTRUCTURE , PHASE TRANSFORMATIONS , SOLIDIFICATION , COOLING , STEEL , THERMAL CYCLING TESTS , ULTRAFINES


Subject Categories : Properties of Metals and Alloys
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE