Sreeja Kumari | Central Electrochemical Research Institute (original) (raw)
Papers by Sreeja Kumari
Journal of Applied Polymer Science, 1997
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006
The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and... more The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and mechanical properties (tensile and impact strength) has been investigated in an Al-7Si-0.3Mg- xFe ( x=0.2, 0.4, and 0.7) alloy. The size of Al-Fe intermetallic platelets (β-Al5FeSi) increased with increasing Fe content. The addition of Ca modified the eutectic microstructure and also reduced the size of intermetallic Fe-platelets, causing improved elongation and impact strengths. A low level of Ca addition (39 ppm) reduced the proosity of the alloys. The tensile strength was decreased marginally with Ca addition. However, Ca addition improved the ductility of the alloy by 18.3, 16.7, and 44 pct and the impact strength by 44, 48, and 15.8 pct for Fe contents of 0.2, 0.4, and 0.7 pct, respectively.
Journal of Alloys and Compounds, 2008
... The higher diffusion coefficient [14] of Si in Al (10 −11 to 10 −8 cm 2 s −1 ) compared to Fe... more ... The higher diffusion coefficient [14] of Si in Al (10 −11 to 10 −8 cm 2 s −1 ) compared to Fe (10 −13 to 10 −12 cm 2 s −1 ) in the temperature range 673873 K would facilitate the destabilization of the β-Al 5 FeSi phase platelets in the presence of Ca. ...
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006
The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and... more The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and mechanical properties (tensile and impact strength) has been investigated in an Al-7Si-0.3Mg-xFe (x=0.2, 0.4, and 0.7) alloy. The size of Al-Fe intermetallic platelets (β-Al5FeSi) increased with increasing Fe content. The addition of Ca modified the eutectic microstructure and also reduced the size of intermetallic Fe-platelets, causing improved elongation and impact strengths. A low level of Ca addition (39 ppm) reduced the proosity of the alloys. The tensile strength was decreased marginally with Ca addition. However, Ca addition improved the ductility of the alloy by 18.3, 16.7, and 44 pct and the impact strength by 44, 48, and 15.8 pct for Fe contents of 0.2, 0.4, and 0.7 pct, respectively.
Journal of Alloys and Compounds, 2008
The modification effect of Ca on the structure and properties of Al-7Si-0.3Mg alloy has been inve... more The modification effect of Ca on the structure and properties of Al-7Si-0.3Mg alloy has been investigated and compared with the well-known modifier, Sr. The optimum level of Ca for achieving modification and best mechanical properties lies in the range of 0.0085-0.017%. Higher amount of Ca than this level leads to the formation of higher porosity and Al-Ca-Si intermetallics. Sr shows more porosity than Ca at 0.018% level in the alloy. The properties obtained with Ca modification are at par with those obtained with the well-known modifier, Sr.
International Materials Reviews, 2005
... composites SS Sreeja Kumari, RM Pillai* and BC Pai The role of calcium in aluminium alloy sys... more ... composites SS Sreeja Kumari, RM Pillai* and BC Pai The role of calcium in aluminium alloy systems is reviewed, commencing with a survey of binary and ternary AlCa(X) alloy systems. ... 1 Phase diagram for AlCa system (courtesy: Itkin et al.3) Sreeja Kumari et al. ...
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
The effects of individual and combined additions of Be, Mn, Ca and Sr on the solidification, stru... more The effects of individual and combined additions of Be, Mn, Ca and Sr on the solidification, structure and mechanical properties of Al-7Si-0.3Mg-0.8Fe alloy has been investigated. Thermal analysis study shows that all additions except Be show a peak corresponding to -Fe intermetallic phase formation. Ca and Sr additions decrease the eutectic temperature (by 6.6 and 8.7 K, respectively) compared to the untreated alloy and lead to modification of eutectic Si from platelet to fibrous form. The peak corresponding to Be-Fe phase has been identified by DTA. Mn (0.4%) and Be (0.2%) additions to Al-7Si-0.3Mg-0.8Fe alloy change the morphology of platelet -phase to script form leading to significant improvement in tensile and both tensile and impact properties, respectively. Addition of Be, Ca and Sr to Mn added Al-7Si-0.3Mg-0.8Fe alloy improves the impact strength significantly due to the modification of the eutectic Si from acicular to fibrous form and refinement of platelet -phase in addition to its morphological change from platelet to Chinese script form. Combined additions of Be + Mn, Ca + Mn and Sr + Mn result in a reduction in the impact strength compared to individual additions of Be, Ca and Sr. The best combinations of both tensile and impact properties have been obtained with the combined additions of Be + Mn, Ca + Mn and Sr + Mn to Al-7Si-0.3Mg-0.8Fe alloy. A trace amount of Be (0.005%) addition to Ca and Sr leads to superior tensile properties compared to individual additions of Ca and Sr.
Journal of Alloys and Compounds, 2011
In situ Al-AlN composite with and without Mg addition was synthesized by nitrogen gas bubbling me... more In situ Al-AlN composite with and without Mg addition was synthesized by nitrogen gas bubbling method. The morphology of the particles was found to be hexagonal by SEM and TEM. The size of the AlN particles was found to be in the range from nano, submicron to a few microns. XRD analysis of the extracted particles confirmed the formation of AlN in the melt. Mg addition enhanced the nitridation rate and formed network of interconnected AlN particles. Hardness of the composite is significantly increased by the hard AlN particles. Further, the mechanism of formation of AlN particles inside the molten aluminium by gas bubbling is discussed.
Journal of Applied Polymer Science, 1997
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006
The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and... more The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and mechanical properties (tensile and impact strength) has been investigated in an Al-7Si-0.3Mg- xFe ( x=0.2, 0.4, and 0.7) alloy. The size of Al-Fe intermetallic platelets (β-Al5FeSi) increased with increasing Fe content. The addition of Ca modified the eutectic microstructure and also reduced the size of intermetallic Fe-platelets, causing improved elongation and impact strengths. A low level of Ca addition (39 ppm) reduced the proosity of the alloys. The tensile strength was decreased marginally with Ca addition. However, Ca addition improved the ductility of the alloy by 18.3, 16.7, and 44 pct and the impact strength by 44, 48, and 15.8 pct for Fe contents of 0.2, 0.4, and 0.7 pct, respectively.
Journal of Alloys and Compounds, 2008
... The higher diffusion coefficient [14] of Si in Al (10 −11 to 10 −8 cm 2 s −1 ) compared to Fe... more ... The higher diffusion coefficient [14] of Si in Al (10 −11 to 10 −8 cm 2 s −1 ) compared to Fe (10 −13 to 10 −12 cm 2 s −1 ) in the temperature range 673873 K would facilitate the destabilization of the β-Al 5 FeSi phase platelets in the presence of Ca. ...
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006
The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and... more The effect of Ca addition on the microstructure, physical characteristics (density/porosity), and mechanical properties (tensile and impact strength) has been investigated in an Al-7Si-0.3Mg-xFe (x=0.2, 0.4, and 0.7) alloy. The size of Al-Fe intermetallic platelets (β-Al5FeSi) increased with increasing Fe content. The addition of Ca modified the eutectic microstructure and also reduced the size of intermetallic Fe-platelets, causing improved elongation and impact strengths. A low level of Ca addition (39 ppm) reduced the proosity of the alloys. The tensile strength was decreased marginally with Ca addition. However, Ca addition improved the ductility of the alloy by 18.3, 16.7, and 44 pct and the impact strength by 44, 48, and 15.8 pct for Fe contents of 0.2, 0.4, and 0.7 pct, respectively.
Journal of Alloys and Compounds, 2008
The modification effect of Ca on the structure and properties of Al-7Si-0.3Mg alloy has been inve... more The modification effect of Ca on the structure and properties of Al-7Si-0.3Mg alloy has been investigated and compared with the well-known modifier, Sr. The optimum level of Ca for achieving modification and best mechanical properties lies in the range of 0.0085-0.017%. Higher amount of Ca than this level leads to the formation of higher porosity and Al-Ca-Si intermetallics. Sr shows more porosity than Ca at 0.018% level in the alloy. The properties obtained with Ca modification are at par with those obtained with the well-known modifier, Sr.
International Materials Reviews, 2005
... composites SS Sreeja Kumari, RM Pillai* and BC Pai The role of calcium in aluminium alloy sys... more ... composites SS Sreeja Kumari, RM Pillai* and BC Pai The role of calcium in aluminium alloy systems is reviewed, commencing with a survey of binary and ternary AlCa(X) alloy systems. ... 1 Phase diagram for AlCa system (courtesy: Itkin et al.3) Sreeja Kumari et al. ...
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
The effects of individual and combined additions of Be, Mn, Ca and Sr on the solidification, stru... more The effects of individual and combined additions of Be, Mn, Ca and Sr on the solidification, structure and mechanical properties of Al-7Si-0.3Mg-0.8Fe alloy has been investigated. Thermal analysis study shows that all additions except Be show a peak corresponding to -Fe intermetallic phase formation. Ca and Sr additions decrease the eutectic temperature (by 6.6 and 8.7 K, respectively) compared to the untreated alloy and lead to modification of eutectic Si from platelet to fibrous form. The peak corresponding to Be-Fe phase has been identified by DTA. Mn (0.4%) and Be (0.2%) additions to Al-7Si-0.3Mg-0.8Fe alloy change the morphology of platelet -phase to script form leading to significant improvement in tensile and both tensile and impact properties, respectively. Addition of Be, Ca and Sr to Mn added Al-7Si-0.3Mg-0.8Fe alloy improves the impact strength significantly due to the modification of the eutectic Si from acicular to fibrous form and refinement of platelet -phase in addition to its morphological change from platelet to Chinese script form. Combined additions of Be + Mn, Ca + Mn and Sr + Mn result in a reduction in the impact strength compared to individual additions of Be, Ca and Sr. The best combinations of both tensile and impact properties have been obtained with the combined additions of Be + Mn, Ca + Mn and Sr + Mn to Al-7Si-0.3Mg-0.8Fe alloy. A trace amount of Be (0.005%) addition to Ca and Sr leads to superior tensile properties compared to individual additions of Ca and Sr.
Journal of Alloys and Compounds, 2011
In situ Al-AlN composite with and without Mg addition was synthesized by nitrogen gas bubbling me... more In situ Al-AlN composite with and without Mg addition was synthesized by nitrogen gas bubbling method. The morphology of the particles was found to be hexagonal by SEM and TEM. The size of the AlN particles was found to be in the range from nano, submicron to a few microns. XRD analysis of the extracted particles confirmed the formation of AlN in the melt. Mg addition enhanced the nitridation rate and formed network of interconnected AlN particles. Hardness of the composite is significantly increased by the hard AlN particles. Further, the mechanism of formation of AlN particles inside the molten aluminium by gas bubbling is discussed.