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Effect of site occupation on thermal and mechanical properties of alloyed Mo5Si3

Erik Ström (Institutionen för material- och tillverkningsteknik) ; Sten G. Eriksson ; Håkan Rundlöf ; Ji Zhang
Acta Materialia Vol. 53 (2005), 2, p. 357-365.
[Artikel, refereegranskad vetenskaplig]

The fundamental thermophysical properties of Mo5Si3 have been investigated. The pronounced mismatch in the coefficient of thermal expansion (CTE) between the c- and a-directions of monolithic Mo5Si3 was reduced significantly by alloying additions. 25 at.% Cr reduced the CTE-mismatch to 1.45 in Mo3Cr2Si3, while 25 at.% Ti resulted in a mismatch of 1.32. Rietveld refinement of neutron powder diffraction data of the studied compounds reveals that Cr, having a smaller radius than Mo, has preference for the 4b chain sites of the D8m unit cell of Mo5Si3. In contrast, Ti atoms, being larger than Mo, occupy almost entirely the 16k sites in the unit cell interior. Compression tests of cast Mo5Si3 at 1573 K indicate that 25% Ti or Nb additions both result in brittle fracture, whereas Mo5Si3 containing 25% Cr deforms plastically. 25% Cr additions decreases the yield strength to approximately half of that of monolithic Mo5Si3 at 1573 K.

Nyckelord: Neutron diffraction; Transition metal silicides; Crystal structure; Brittle-to-ductile transition; High temperature deformation



Denna post skapades 2006-08-25. Senast ändrad 2010-01-26.
CPL Pubid: 11709

 

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Institutioner (Chalmers)

Institutionen för material- och tillverkningsteknik

Ämnesområden

Materialteknik

Chalmers infrastruktur