BARC/PUB/2013/0259

 
 

Effect of Co Addition on the Microstructure, Martensitic Transformation and Shape Memory Behavior of Fe-Mn-Si Alloys

 
     
 
Author(s)

Maji, B. C.; Krishnan, M.; Sujata, M.; Gouthama; Ray, R. K.
(MSD)

Source

Metallurgical & Materials Transactions-A, 2013. Vol. 44 (1): pp. 172-185

ABSTRACT

The effect of Co addition has been studied in Fe-30Mn-6Si-xCo (x = 0 to 9 wt pct) shape memory alloys in terms of their microstructure, martensitic transformation and shape recovery. Microstructural investigations reveal that in Fe-Mn-Si-Co alloys, the microstructure remains single-phase austenite (γ) up to 5 pct Co and beyond that becomes two-phase comprising c and off-stoichiometric (Fe,Co)5Mn3Si2 intermetallic Π-phases. The forward γ-ε martensite  transformation start temperature (MS) decreases with the addition of Co up to 5 pct, and alloys containing more than 5 pct Co, show slightly higher MS possibly on account of two-phase microstructure. UnlikeMS, the  ε-Υ reverse transformation start temperature (AS) has been found to remain almost unaltered by Co addition. In general, addition of Co to Fe-Mn-Si alloys deteriorates shape recovery due to decreasing resistance to plastic yielding concomitant with the formation of stress induced e martensite. However, there is an improvement in shape recovery beyond 5 pct Co addition, possibly due to the strengthening effect arising from the presence of (Fe,Co)5Mn3Si2 precipitates within the two-phase microstructure and due to higher amount of stress induced ε martensite.

 
 
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