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Developing Mg–Zn surface alloy by friction surface allosying: In vitro degradation studies in simulated body fluids

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International Journal of Minerals,Metallurgy and Materials 2020年第7期27卷 962-969页

作者： Venkateswarlu badisha Shabana Shaik Ravikumar Dumpala b.ratna sunil Department of Metallurgical and Materials Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India Department of Mechanical Engineering Bapatla Engineering CollegeBapatla 522101India

A new variant of friction-assisted process named friction surface alloying(FSA)for developing surface alloys was demonstrated in the present *** FSA,the dispersed phase is melted and allowed to react with the matrix material to form an alloy at the surface of a metallic *** the present work,magnesium(Mg)sheets and zinc(Zn)powder were selected,and fine grained(~3.5μm)Mg–Zn surface alloy with improved hardness was produced by FSA.X-ray diffraction studies confirmed the formation of intermetallic phases of Mg and Zn at the *** the in vitro degradation studies carried out by immersing in simulated body fluids,a lower corrosion rate was observed for the Mg–Zn surface alloy compared with pure *** surface morphologies after immersion studies indicated large degraded areas on the base Mg compared with Mg–*** results demonstrate the potential of FSA in developing Mg-based surface alloys without melting the substrate to impart better surface properties.

关键词： friction stir processing,surface alloy magnesium zinc corrosion degradation

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

Magnesium based surface metal matrix composites by friction stir processing

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Journal of Magnesium and Alloys 2016年第1期4卷 52-61页

作者： b.ratna sunil G.Pradeep Kumar Reddy Hemendra Patle Ravikumar Dumpala Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 520202India Department of Mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India

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 *** potential applications of the surface MMCs can be found in automotive,aerospace,biomedical and power ***,friction stir processing(FSP)technique has been gaining wide popularity in producing surface composites in solid state *** and its alloys being difficult to process metals also have been successfully processed by FSP to fabricate surface *** aim of the present paper is to provide a comprehensive summary of state-of-the-art in fabricating magnesium based composites by *** of the secondary phase particles and grain refinement resulted from FSP on the properties of these composites is also discussed.

关键词： Surface composites Friction stir processing Hardness Light weight Magnesium alloys biomedical implants

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

Diverse roles of bitter melon(Momordica charantia)in prevention of oral cancer

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Journal of Cancer Metastasis and Treatment 2021年第1期7卷 178-188页

作者： Subhayan Sur ratna b.Ray Department of Pathology Saint Louis UniversitySt.LouisMO 63104USA. Cancer Center Saint Louis UniversitySt.LouisMO 63104USA

Oral squamous cell carcinoma(OSCC)is one of the common lethal malignancies which is increasing rapidly in the *** risks from alcohol and tobacco habits,lack of early detection markers,lack of effective chemotherapeutic agents,recurrence and distant metastasis make the disease more complicated to ***-based studies and epidemiological studies indicate important roles of nutraceuticals to manage different *** plant bitter melon(Momordica charantia)is a good source of nutrients and bio-active phytochemicals such as triterpenoids,triterpene glycosides,phenolic acids,flavonoids,lectins,sterols and *** plant is widely grown in Asia,Africa,and South *** melon has traditionally been used as a folk medicine and Ayurvedic medicine in Asian culture to treat diseases such as diabetes,since ancient *** crude extract and some of the isolated pure compounds of bitter melon show potential anticancer effects against different *** this review,we shed light on its effect on *** melon extract has been found to inhibit cell proliferation and metabolism,induce cell death and enhance the immune defense system in the prevention of OSCC in vitro and in ***,bitter melon may be used as an attractive chemopreventive agent in progression towards OSCC clinical study.

关键词： bitter melon(Momordica charantia) oral squamous cell carcinoma signal transduction cancer metabolism immune system cancer prevention

Comparison of the effects of different protocols on the particle size distribution of TiO_2 dispersions

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Particuology 2015年第2期13卷 35-44页

作者： ratna Tantra Aneta Sikora Nanna b.Hartmann Juan Riego Sintes Kenneth N.Robinson National Physical Laboratory European Commission DG Joint Research Centre

There is a need to standardize methods associated with the dispersion of nanomaterials in nano（eco）toxicological investigations. The first step toward this goal is to understand the degree of variability that exists in nanomaterial dispersions prepared by using different protocols. Using two case studies, the degree of variability in TiO2 nanomaterial dispersions was assessed by differential centrifugal sedimentation （DCS） methods. Case study 1 addresses the variability that arises from variations within one protocol, investigating the effects of dispersion aging, sonication exposure time, sonication in the presence/absence of an ice bath, material subsampling, particle concentration and having a pre-wetting step. Case study 2 addresses the variability between four different protocols developed through past research activities and projects. The results indicate that there is a large degree of variability （relative standard deviation （RSD） of mean particle diameter = 26%） in the dispersion ofTiO2 nanornaterials between the four different protocols studied and that several steps in a dispersion protocol are potential sources of variation, with final particle concentration being the most significant. The implication of this study is clear： for the purpose of data comparability, there is a need to provide the exact details of all steps involved in a dispersion protocol.

关键词： Nanoparticle Dispersion Protocol Differential centrifugal sedimentation Nano(eco)toxicology

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