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| 1 | Influence of bimodal grain size distribution on the corrosion behavior of friction stir processed biodegradable AZ31 magnesium alloy显示文摘In the present study,AZ31 magnesium alloy sheets were processed by friction stir processing(FSP)to investigate the effect of the grain refinement and grain size distribution on the corrosion behavior.Grain refinement from a starting size of 16.4±6.8µm to 3.2±1.2µm was attained after FSP.Remarkably,bimodal grain size distribution was observed in the nugget zone with a combination of coarse(11.62±8.4µm)and fine grains(3.2±1.2µm).Due to the grain refinement,a slight improvement in the hardness was found in the nugget zone of FSPed AZ31.The bimodal grain size distribution in the stir zone showed pronounced influence on the corrosion rate of FSPed AZ31 as observed from the immersion and electrochemical tests.From the X-ray diffraction analysis,more amount of Mg(OH)_(2) was observed on FSPed AZ31 compared with the unprocessed AZ31.Polarization measurements demonstrated the higher corrosion current density for FSPed AZ31(8.92×10^(−5)A/cm^(2))compared with the unprocessed condition(2.90×10^(−5)A/cm^(2))that can be attributed to the texture effect and large variations in the grain size which led to non-uniform galvanic intensities. | N.Saikrishna G.Pradeep Kumar Reddy Balakrishnan Munirathinam B.Ratna Sunil | 2016 | Journal of Magnesium and Alloys2016，4，1： | 13 |
| 2 | Magnesium based surface metal matrix composites by friction stir processing显示文摘Surface metal matrix composites(MMCs)are a group of modern engineered materials where the surface of the material is modified by dispersing secondary phase in the form of particles or fibers and the core of the material experience no change in chemical composition and structure.The potential applications of the surface MMCs can be found in automotive,aerospace,biomedical and power industries.Recently,friction stir processing(FSP)technique has been gaining wide popularity in producing surface composites in solid state itself.Magnesium and its alloys being difficult to process metals also have been successfully processed by FSP to fabricate surface MMCs.The aim of the present paper is to provide a comprehensive summary of state-of-the-art in fabricating magnesium based composites by FSP.Influence of the secondary phase particles and grain refinement resulted from FSP on the properties of these composites is also discussed. | B.Ratna Sunil G.Pradeep Kumar Reddy Hemendra Patle Ravikumar Dumpala | 2016 | Journal of Magnesium and Alloys2016，4，1： | 6 |
| 3 | Effect of aluminum content on machining characteristics of AZ31 and AZ91 magnesium alloys during drilling显示文摘Magnesium(Mg)and its alloys are now becoming the promising choice for various structural applications due to their low density and high specific strength compared with other light metals such as aluminum and its alloys.Among all Mg alloys,AZ(aluminum and zinc)series is the most widely used alloy system for various structural applications.But,machining of magnesium and its alloys involves certain issues due to their brittle nature and risk of inflammability unlike other nonferrous metals.Particularly,alloys with considerable amount of secondary phase may exhibit different machining characteristics during metal cutting operations.In the present study,two AZ series alloys AZ31 and AZ91 were selected and drilling operation was performed to assess the effect of the secondary phase amount and distribution on machining characteristics.Drilling operation was carried out at different sets of process parameters and cutting forces were obtained and the chips which have been produced during drilling were analyzed.From the results,it can be clearly understood that the presence of secondary phase(Mg_(17)Al_(12))has a significant influence on cutting forces.Increase in cutting speed has reduced the required cutting force and load fluctuations in all the cases. | B.Ratna Sunil K.V.Ganesh P.Pavan G.Vadapalli Ch Swarnalatha P.Swapna P.Bindukumar G.Pradeep Kumar Reddy | 2016 | Journal of Magnesium and Alloys2016，4，1： | 4 |
| 4 | An investigation on the hardness and corrosion behavior of MWCNT/Mg composites and grain refined Mg显示文摘In the present work,multi walled carbon nanotubes(MWCNT)reinforced magnesium(Mg)matrix composite was fabricated by friction stir processing(FSP)with an aim to explore its mechanical and electrochemical behavior.Microstructural observations showed that the thickness of the produced composite layer was in the range of 2500μm.FSP resulted uniform distribution of CNT near the surface while agglomerated layers in the subsurface.Grain refinement of Mg achieved by FSP improved the hardness but significant enhancement in the hardness value was observed for FSPed MWCNT/Mg composites.Potentiodynamic polarization studies revealed that the increase in corrosion current density was observed for MWCNT/Mg composite compared with grain refined Mg and pure Mg,implying the significance of secondary phase(MWCNT)in decreasing the corrosion resistance of the composite. | N.Saikrishna G.Pradeep Kumar Reddy Balakrishnan Munirathinam Ravikumar Dumpala M.Jagannatham B.Ratna Sunil | 2018 | Journal of Magnesium and Alloys2018，6，1： | 4 |
| 5 | Joining of AZ31 and AZ91 Mg alloys by friction stir welding显示文摘Two dissimilar magnesium(Mg)alloy sheets,one with low aluminium(AZ31)and another with high aluminium(AZ91)content,were successfully joined by friction stir welding(FSW).The effect of process parameters on the formation of hot cracks was investigated.A sound metallurgical joint was obtained at optimized process parameters(1400 rpm with 25 mm/min feed)which contained fine grains and distributed β(Mg_(17)Al_(12))phase within the nugget zone.An increasing trend in the hardness measurements has also confirmed more amount of dissolution of aluminium within the nugget zone.A sharp interface between nugget zone and thermo mechanical affected zone(TMAZ)was clearly noticed at the AZ31 Mg alloy side(advancing)but not on the AZ91 Mg alloy side(retreating).From the results it can be concluded that FSW can be effectively used to join dissimilar metals,particularly difficult to process metals such as Mg alloys,and hot cracking can be completely eliminated by choosing appropriate process parameters to achieve sound joint. | B.Ratna Sunil G.Pradeep Kumar Reddy A.S.N.Mounika P.Navya Sree P.Rama Pinneswari I.Ambica R.Ajay Babu P.Amarnadh | 2015 | Journal of Magnesium and Alloys2015，3，4： | 3 |
| 6 | Joining of AZ91 Mg alloy and Al6063 alloy sheets by friction stir welding显示文摘In the present work,the effect of process parameters on joining of AZ91 Mg alloy and Al6063 aluminum alloy sheets during friction stir welding(FSP)was studied.A successful joint was achieved at 1100 r.p.m.tool rotational speed and 25 mm/min tool travel speed.Combination of tool rotational speed and tool travel speed has observed a profound effect on the material flow mechanisms at the nugget zone.From the microstructural studies,the joint formation was observed as mainly due to mechanical mixing of the materials.The level of metallurgical continuity at the nugget zone was observed as poor and a sharp interface at the joint was noticed.The microhardness measurements across the weld joint also revealed the lack of establishment of a perfect metallurgical bonding.X-ray diffraction analysis of weld zone showed presence of both magnesium and aluminum.Hence from the preliminary observations,it can be understood that the joining of AZ91 Mg alloy and Al6063 alloy can be achieved by FSP;however,complex issues in material mixing still need further investigations. | B.Lakshmana Prasad G.Neelaiah M.Gopi Krishna S.V.V.Ramana K.Sai Prakash G.Sarika G.Pradeep Kumar Reddy Ravikumar Dumpala B.Ratna Sunil | 2018 | Journal of Magnesium and Alloys2018，6，1： | 2 |
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