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Influence of bimodal grain size distribution on the corrosion behavior of friction stir processed biodegradable AZ31 magnesium alloy

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Journal of Magnesium and Alloys 2016年第1期4卷 68-76页

作者： N.Saikrishna g.pradeep kumar reddy balakrishnan Munirathinam b.ratna sunil Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India Department of Metallurgical and Materials Engineering Indian Institute of Technology MadrasChennai 600036India

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 *** refinement from a starting size of 16.4±6.8µm to 3.2±1.2µm was attained after ***,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 *** 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 *** the X-ray diffraction analysis,more amount of Mg(OH)_(2) was observed on FSPed AZ31 compared with the unprocessed *** 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.

关键词： AZ31 Mg alloy biodegradable implants grain size distribution Corrosion Friction stir processing,texture

An investigation on the hardness and corrosion behavior of MWCNT/Mg composites and grain refined Mg

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Journal of Magnesium and Alloys 2018年第1期6卷 83-89页

作者： N.Saikrishna g.pradeep kumar reddy balakrishnan Munirathinam Ravikumar Dumpala M.Jagannatham b.ratna sunil Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 520201India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India Department of Metallurgical and Materials Engineering Indian Institute of Technology MadrasChennai 600036India Department of Mechanical Engineering Visvesvaraya National Institute of Technology(VNIT)Nagpur 440010India Reactor Engineering Division Bhabha Atomic Research CentreMumbai-400085India Department of Materials Science and Engineering Department Delft University of TechnologyDelftNetherlands

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 *** observations showed that the thickness of the produced composite layer was in the range of 2500μ*** resulted uniform distribution of CNT near the surface while agglomerated layers in the *** refinement of Mg achieved by FSP improved the hardness but significant enhancement in the hardness value was observed for FSPed MWCNT/Mg *** 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.

关键词： Friction stir processing MWCNT/Mg composite Hardness basal texture Corrosion resistance

A review on developing high-performance ZE41 magnesium alloy by using bulk deformation and surface modification methods

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Journal of Magnesium and Alloys 2023年第3期11卷 776-800页

作者： Subrat kumar baral Manjusha M.Thawre b.ratna sunil Ravikumar Dumpala Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India Department of Metallurgical and Materials Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India Department of Mechanical Engineering Bapatla Engineering CollegeBapatla 522102India

Magnesium(Mg)alloys are generally used in light-weight structural applications due to their higher specific ***,the usage of these Mg alloys is limited due to their poor formability at room temperature,which is attributed to lower count of slip systems associated with the hcp crystal *** address these limitations,several new magnesium alloys and also many processing strategies have been developed and reported in the ***41 Mg is an alloy with significant quantities of zinc(Zn)and rare earth(RE)elements and has emerged as a promising material for aerospace,automotive,electronics,biomedical and many other *** make this alloy more competitive and viable,it should possess better mechanical and corrosion ***,the current paper reviews the effect of bulk mechanical processing on grain refinement,microstructural modification,and corresponding changes in the mechanical behaviour of ZE41Mg ***,the effect of various surface modification techniques on altering the surface microstructure and surface properties such as wear and corrosion are also briefly summarized and *** review also discusses the challenges and the future perspectives in developing high-performing ZE41 Mg alloys.

关键词： ZE41 magnesium alloy bulk deformation Surface modification Mechanical properties Wear Corrosion

Effect of aluminum content on machining characteristics of AZ31 and AZ91 magnesium alloys during drilling

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Journal of Magnesium and Alloys 2016年第1期4卷 15-21页

作者： b.ratna sunil K.V.ganesh P.Pavan g.Vadapalli Ch Swarnalatha P.Swapna P.bindukumar g.pradeep kumar reddy Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India

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 *** all Mg alloys,AZ(aluminum and zinc)series is the most widely used alloy system for various structural ***,machining of magnesium and its alloys involves certain issues due to their brittle nature and risk of inflammability unlike other nonferrous ***,alloys with considerable amount of secondary phase may exhibit different machining characteristics during metal cutting *** 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 *** 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 *** the results,it can be clearly understood that the presence of secondary phase(Mg_(17)Al_(12))has a significant influence on cutting *** in cutting speed has reduced the required cutting force and load fluctuations in all the cases.

关键词： Light metals Magnesium Drilling AZ series Cutting force Compounds

Joining of AZ91 Mg alloy and Al6063 alloy sheets by friction stir welding

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Journal of Magnesium and Alloys 2018年第1期6卷 71-76页

作者： 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 Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 520201India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India

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 *** rotational speed and 25 mm/min tool travel *** of tool rotational speed and tool travel speed has observed a profound effect on the material flow mechanisms at the nugget *** the microstructural studies,the joint formation was observed as mainly due to mechanical mixing of the *** level of metallurgical continuity at the nugget zone was observed as poor and a sharp interface at the joint was *** 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 *** 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.

关键词： Friction stir welding Dissimilar joints Magnesium Aluminum Nugget zone

Joining of AZ31 and AZ91 Mg alloys by friction stir welding

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Journal of Magnesium and Alloys 2015年第4期3卷 330-334页

作者： b.ratna sunil.g.pradeep kumar reddy A.S.N.Mounika P.Navya Sree P.Rama Pinneswari I.Ambica R.Ajay babu P.Amarnadh Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India

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 *** 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.

关键词： Dissimilar metal joining Magnesium alloys Friction stir welding AZ31 AZ91

Influence of heat treatment on the machinability and corrosion behavior of AZ91 Mg alloy

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Journal of Magnesium and Alloys 2018年第1期6卷 52-58页

作者： Swetha Chowdary V Ravikumar Dumpala Anand kumar S Kondaiah VV ratna sunil b Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid521202India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpurMaharashtra 440010India Department of Mechanical Engineering Dayananda Sagar UniversityBengaluru560068India Department of Mechanical Engineering Tirumala Engineering CollegeNarasaraopetAndhra Pradesh 522601India

In the present study,AZ91 Mg alloy was heat treated at 410℃ for 6,12 and 24 h to investigate the influence of heat treatment on machinability and corrosion *** effect of soaking time on the amount and distribution of Mg 17 Al 12(β-phase)was analyzed under the optical *** measurements demonstrated the increased hardness with increased heat treatment soaking time,which can be attributed to the solid solution *** influence of super saturatedα-grains on reducing the cutting force(F z)with respect to increased cutting speed was observed as *** corrosion behavior of the heat treated specimens was studied by conducting electrochemical ***,corrosion rate of heat treated samples was observed as increased compared with the base *** the results,it is evident that the machinability of AZ91 Mg alloy can be improved by producing super saturatedα-grains through heat treatment but at the cost of losing corrosion resistance.

关键词： AZ91 Mg alloy Solid solution Turning Corrosion Machinability

Enhanced Energy Efficient with a Trust Aware in MANET for Real-Time Applications

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Computers, Materials & Continua 2023年第4期75卷 587-607页

作者： M.V.Narayana Vadla pradeep kumar Ashok kumar Nanda Hanumantha Rao Jalla Subba reddy Chavva Department of CSE Guru Nanak Institutions Technical CampusHyderabadRanga Reddy DistrictTelangana501506India Department of CSE B V Raju Institute of TechnologyNarsapurMedakTelangana502313India Department of CSE T.R.R.Government Degree College KandukurKandukurA.P.523105India Department of IT VFST&Research(Deemed to be University)VadlamudiA.P.522213India

Mobile ad hoc networks (MANETs) are subjected to attack detectionfor transmitting and creating new messages or existing message *** attacker on another node evaluates the forging activity in themessage directly or indirectly. Every node sends short packets in a MANETenvironment with its identifier, location on the map, and time through *** attackers on the network broadcast the warning message usingfaked coordinates, providing the appearance of a network collision. Similarly,MANET degrades the channel utilization performance. Performancehighly affects network performance through security algorithms. This paperdeveloped a trust management technique called Enhanced beacon TrustManagement with Hybrid Optimization (EbTM-Hyopt) for efficient clusterhead selection and malicious node detection. It tries to build trust amongconnected nodes and may improve security by requiring every participatingnode to develop and distribute genuine, accurate, and trustworthy materialacross the network. Specifically, optimized cluster head election is done periodicallyto reduce and balance the energy consumption to improve the lifetimenetwork. The cluster head election optimization is based on hybridizingParticle Swarm Optimization (PSO) and gravitational Search OptimizationAlgorithm (gSOA) concepts to enable and ensure reliable routing. Simulationresults show that the proposed EbTM-HYOPT outperforms the state-of-thearttrust model in terms of 297.99 kbps of throughput, 46.34% of PDR, 13%of energy consumption, 165.6 kbps of packet loss, 67.49% of end-to-end delay,and 16.34% of packet length.

关键词： MANET malicious nodes clustering trust management beacon message

Machining characteristics of fine grained AZ91 Mg alloy processed by friction stir processing

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Transactions of Nonferrous Metals Society of China 2017年第4期27卷 804-811页

作者： g.V.V.SURYA KIRAN K.HARI KRISHNA Sk.SAMEER M.bHARgAVI b.SANTOSH kumar g.MOHANA RAO Y.NAIDUbAbU RAVIkumar DUMPALA b.ratna sunil Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies (AP-IIIT) Nuzvid 521202 India Department of Mechanical Engineering Visvesvaraya National Institute of Technology Nagpur 440010 India

AZ91Mg alloy was considered and friction stir processing(FSP)was adopted to achieve grain refinement to investigatethe effect of grain size and secondary phase on machining characteristics during drilling at various speeds and *** saturatedAZ91Mg alloy was obtained after FSP and the grain refinement was achieved from(166.5±8.7)μm to(21.7±13.5)μ***,hardness reduced for FSP AZ91Mg alloy(88.95±6.1)compared with AZ91alloy(108.2±15.6),which was attributed to the reducedsecondary ***,the mean cutting force for FSP-treated(FSPed)AZ91Mg alloy was marginally *** edgedamage of the drilled holes was lower for FSPed AZ91Mg alloy compared with unprocessed AZ91Mg ***,it can beunderstood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achievedin machining of AZ91Mg alloy.

关键词： magnesium alloy friction stir processing machining grain size microstructure