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Process parameters-weld bead geometry interactions and their influence on mechanical properties:A case of dissimilar aluminium alloy electron beam welds

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Defence Technology（防务技术） 2018年第2期14卷 137-150页

作者： P.Mastanaiah Abhay Sharma g.madhusudhan reddy Defence Research and Development Laboratory KanchanbaghHyderabadTelangana 500058India Indian Institute of Technology Hyderabad Kandi CampusSangareddyTelangana 502285India Defence Metallurgical Research Laboratory KanchanbaghHyderabadTelangana 500058India

Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the load bearing capability of a weld joint, which in-turn decides the performance in real time service conditions. The present study introduces a novel approach of detecting a relationship between weld bead geometry and mechanical properties(e.g. tensile load) for the purpose of catering the best the process could offer. The significance of the proposed approach is demonstrated by a case of dissimilar aluminium alloy(AA2219 and AA5083) electron beam welds. A mathematical model of tensile braking load as a function of geometrical attributes of weld bead geometry is presented. The results of investigation suggests the effective thickness of weld-a geometric parameter of weld bead has the most significant influence on tensile breaking load of dissimilar weld joint. The observations on bead geometry and the mechanical properties(microhardness, ultimate tensile load and face bend angle) are correlated with detailed metallurgical analysis. The fusion zone of dissimilar electron beam weld has finer grain size with a moderate evaporation and segregation of alloying elements magnesium and copper *** mechanical properties of weld joint are controlled by optimum bead geometry and HAZ softening in weaker AA5083 Al alloy.

关键词： Electron beam welding AA2219 AA5083 Bead geometry Tensile breaking load

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Cold Cracking of Flux Cored Arc Welded Armour grade High Strength Steel Weldments

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Journal of Materials Science & Technology 2009年第4期25卷 516-526页

作者： g.Magudeeswaran V.Balasubramanian g.madhusudhan reddy Metal Joining Research Center(MJRC) Sri Ramakrishna Engineering College Centre for Materials Joining & Research(CEMAJOR) Department of Manufacturing EngineeringAnnamalai University Metal Joining Section Defence Metallurgical Research Laboratory(DMRL)

In this investigation, an attempt has been made to study the influence of welding consumables on the factors that influence cold cracking of armour grade quenched and tempered （Q＆.T） steel welds. Flux cored arc welding （FCAW） process were used making welds using austenitic stainless steel （ASS） and low hydrogen ferritic steel （LHF） consumables. The diffusible hydrogen levels in the weld metal of the ASS and LHF consumables were determined by mercury method. Residual stresses were evaluated using X-ray stress analyzer and implant test was carried out to study the cold cracking of the welds. Results indicate that ASS welds offer a greater resistance to cold cracking of armour grade Q＆T steel welds.

关键词： Quenched and tempered steel Flux cored arc welding process Weld cold cracking Implant testing

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Influence of welding consumables on tensile and impact properties of multi-pass SMAW Armox 500T steel joints vis-a-vis base metal

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Defence Technology（防务技术） 2018年第3期14卷 188-195页

作者： Ambuj Saxena A.Kumaraswamy g.madhusudhan reddy Vemuri Madhu Defence Institute of Advanced Technology(DU) Pune 411025India Defence Metallurgical Research Laboratory KanchanbaghHyderabad 500048India

In this investigation, comparative study of tensile and impact properties of multi-pass SMAW Armox500 T steel joints fabricated by austenitic stainless steel(ASS) and low hydrogen ferritic steel(LHF)consumables vis-a-vis base metal was carried out. The tensile tests were conducted on computer controlled Walter t Bai Ag UTM at a nominal strain rate of 10à3 sà1. Subsequently, charpy impact tests were carried out on an instrumented Zwick-Roell test setup to obtain load vs. displacement and maximum energy absorbed vs. displacement of the specimen. It was observed that, the joint efficiency of weldment processed by LHF consumable was 41.7% and weldment processed by ASS was 30.6% of its base metal indicating the influence of electrode consumable on tensile properties of the joints. On the contrary, impact toughness of weldment processed by ASS was 20% more and weldment processed by LHF was 12% less than that of base metal. Microstructural studies also revealed that, ASS can be considered as a candidate welding consumable for good strain hardening and toughness of the welding joint in impact applications. However, LHF steel consumable is recommended for welding joints that requires higher joint efficiency under tensile loading conditions.

关键词： SMAW 不锈钢金属相焊接张力关节性质传递

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Experimental Investigation on the Performance of Armour grade Q&T Steel Joints Fabricated by Flux Cored Arc Welding with Low Hydrogen Ferritic Consumables

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Journal of Materials Science & Technology 2009年第5期25卷 583-591页

作者： g.Magudeeswaran V.Balasubramanian g.madhusudhan reddy g.gopalakrishnan Metal Joining Research Center(MJRC) Sri Ramakrishna Engineering CollegeN.G.G.O Colony-Post Centre for Materials Joining&Research(CEMAJOR) Department of Manufacturing EngineeringAnnamalai University Scientist-F Metal Joining SectionDefence Metallurgical Research Laboratory(DMRL)Kanchanbagh(P.O)

Quenched and Tempered （Q＆T） steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. These steels are prone to hydrogen induced cracking （HIC） and softening in the heat affected zone （HAZ） after welding. The use of austenitic stainless steel （ASS） consumables to weld the above steel was the only available remedy to avoid HIC because of higher solubility for hydrogen in austenitic phase. Recent studies revealed that low hydrogen ferritic （LHF） steel consumables can also be used to weld Q＆T steels, which can give very low hydrogen levels in the weld deposits and required resistance against cold cracking. Hence, in this investigation an attempt has been made to study the performance of armour grade Q＆T steel joints fabricated by flux cored arc welding with LHF steel consumables. Two different consumables namely （i） austenitic stainless steel and （ii） low hydrogen ferritic steel have been used to fabricate the joints by flux cored arc welding （FCAW） process. The joints fabricated by LHF consumable exhibited superior transverse tensile properties due to the presence of ferrite microstructure in weld metal. The joints fabricated by ASS consumable showed higher impact toughness due to the presence of austenitic phase in weld metal microstructure. The HAZ softening in coarse grain heat affected zone （CgHAZ） is less in the joints fabricated using LHF consumable due to the lower heat input involved during fabrication compared to the joints fabricated using ASS consumables.

关键词： Quenched and tempered steel Flux cored arc welding process Low hydrogen ferritic steel Tensile properties

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Welding of nickel free high nitrogen stainless steel: Microstructure and mechanical properties

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Defence Technology（防务技术） 2017年第2期13卷 59-71页

作者： Raffi Mohammed g.madhusudhan reddy K.Srinivasa Rao Department of Metallurgical Engineering Andhra University Visakhapatnam India Defence Metallurgical Research Laboratory Hyderabad India

High nitrogen stainless steel(HNS) is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grade steel owing to its low cost, excellent mechanical properties and better corrosion *** fusion welding causes problems like nitrogen desorption, solidification cracking in weld zone, liquation cracking in heat affected zone, nitrogen induced porosity and poor mechanical *** above problems can be overcome by proper selection and procedure of joining process. In the present work, an attempt has been made to correlate the microstructural changes with mechanical properties of fusion and solid state welds of high nitrogen steel. Shielded metal arc welding(SMAW), gas tungsten arc welding(gTAW), electron beam welding(EBW) and friction stir welding(FSW) processes were used in the present work. Optical microscopy, scanning electron microscopy and electron backscatter diffraction were used to characterize microstructural changes. Hardness, tensile and bend tests were performed to evaluate the mechanical properties of welds. The results of the present investigation established that fully austenitic dendritic structure was found in welds of SMAW. Reverted austenite pools in the martensite matrix in weld zone and unmixed zones near the fusion boundary were observed in gTA welds. Discontinuous ferrite network in austenite matrix was observed in electron beam *** recrystallized austenite grain structure was observed in the nugget zone of friction stir *** mechanical properties are obtained in friction stir welds when compared to fusion welds. This is attributed to the refined microstructure consisting of equiaxed and homogenous austenite grains.

关键词： High nitrogen austenitic stainless steel(HNS) Shielded metal arc welding (SMAW) gas tungsten arc welding (gTAW) Electron beam welding (EBW) Friction stir welding (FSW)

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Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing-An experimental study and analytical approach

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Defence Technology（防务技术） 2016年第1期12卷 25-31页

作者： I.SUDHAKAR g.madhusudhan reddy K.SRINIVASA RAO department of mechanical engineering mvgrceVizianagaramIndia defence metallurgical research laboratory HyderabadIndia department of metallurgical engineering andhra universityVisakhapatnamIndia

High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir *** performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was

关键词： AA7075 aluminium alloy Friction stir processing(FSP) Surface metal matrix composite(SMMC) Boron carbide(B4C) Ballistic performance Target

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Improvement of Microstructure and Mechanical Behavior of gas Tungsten Arc Weldments of Alloy C-276 by Current Pulsing

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Acta Metallurgica Sinica(English Letters) 2015年第2期28卷 208-215页

作者： M.Manikandan N.Arivazhagan M.Nageswara Rao g.madhusudhan reddy School of Mechanical and Building Sciences VIT University Defence Metallurgical and Research Laboratory

Superalloy C-276 is known to be prone to hot cracking during fusion welding by gas Tungsten Arc method. Microsegregation occurring during cooling of fusion zone with consequent appearance of topologically close-packed phases P and IX has been held responsible for the observed hot cracking. The present work investigated the possibility of suppressing the microsegregation in weldments by resorting to current pulse. Weldments were made by continuous current gas tungsten arc welding and pulsed current gas tungsten arc welding using ERNiCrMo-4 filler wire. The weld joints were studied with respect to microstructure, microsegregation, and mechanical properties. Optical microscopy and scanning electron microscopy were employed to study the microstructure. Energy-Dispersive X-ray Spectroscopy was carried out to evaluate the extent of microsegregation. Tensile testing was carried out to determine the strength and ductility. The results show that the joints fabricated with pulsed current gave rise to narrower welds with practically no heat affected zone, a refined microstructure in the fusion zone, reduced microsegregation, and superior combination of mechanical properties.

关键词： Alloy C-276 Pulsed current gas tungsten arc welding Microsegregation

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Friction welding of AA6061 to AISI 4340 using silver interlayer

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Defence Technology（防务技术） 2015年第3期11卷 292-298页

作者： SURESH D.MESHRAM g.madhusudhan reddy Defence Metallurgical Research Laboratory

The present work pertains to the study on joining of AA6061 and AISI 4340 through continuous drive friction welding. The welds were evaluated by metallographic examination, X-ray diffraction, electron probe microanalysis, tensile test and microhardness. The study reveals that the presence of an intermetallic compound layer at the bonded interface exhibits poor tensile strength and elongation. Mg in AA6061 near to the interface is found to be favourable for the formation and growth of Fe2Al5 intermetallics. Introduction of silver as an interlayer through electroplating on AISI 4340 resulted in accumulation of Si at weld interface, replacing Mg at AA6061 side, thereby reducing the width of intermetallic compound layer and correspondingly increasing the tensile strength. Presence of silver at the interface results in partial replacement of Fe-Al based intermetallic compounds with Ag-Al based compounds. The presence of these intermetallics was confirmed by X-ray diffraction technique. Since Ag-Al phases are ductile in nature, tensile strength is not deteriorated and the silicon segregation at weld interface on AA6061 in the joints with silver interlayer acts as diffusion barrier for Fe and further avoids formation of Fe-Al based intermetallics. A maximum tensile strength of 240 MPa along with 4.9% elongation was obtained for the silver interlayer dissimilar metal welds. The observed trends in tensile properties and hardness were explained in relation to the microstructure.

关键词： AISI 摩擦焊接金属间化合物层 X-射线衍射技术银焊接界面博士夹层

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ZrB_(2)-SiC based composites for thermal protection by reaction sintering of ZrO_(2)+B_(4)C+Si

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Journal of Advanced Ceramics 2017年第4期6卷 320-329页

作者： R.V.KRISHNARAO V.V.BHANUPRASAD g.madhusudhan reddy Defence Metallurgical Research Laboratory KanchanbaghHyderabad-500058India

Synthesis and sintering of ZrB_(2)-SiC based composites have been carried out in a single-step pressureless reaction sintering(PLRS)of ZrO_(2),B_(4)C,and Si.Y_(2)O_(3) and Al_(2)O_(3) were used as sintering *** effect of ratios of ZrO_(2)/B_(4)C,ZrO_(2)/Si,and sintering additives(Y_(2)O_(3) and Al_(2)O_(3)),was studied by sintering at different temperatures between 1500 and 1680℃in argon ***_(2),SiC,and YAg phases were identified in the sintered *** as high as 4.2 g/cm^(3),micro hardness of 12.7 gPa,and flexural strength of 117.6 MPa were obtained for PLRS *** material was also prepared by PLRS for tungsten inert gas(TIg)welding of the ZrB_(2)-SiC based *** shear strength of the weld was 63.5 *** PLRS ZrB_(2)-SiC composites exhibited:(i)resistance to oxidation and thermal shock upon exposure to plasma flame at 2700℃for 600 s,(ii)thermal protection for Cf-SiC composites upon exposure to oxy-propane flame at 2300℃for 600 s.

关键词： ZrB_(2) SiC reactive sintering synthesis composites

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gas tungsten arc welding of ZrB_2-SiC based ultra high temperature ceramic composites

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Defence Technology（防务技术） 2015年第3期11卷 188-196页

作者： R.V.KRISHNARAO g.madhusudhan reddy Defence Metallurgical Research Laboratory

The difficulty in fabricating the large size or complex shape limits the application of ZrB2-SiC composites. Joining them by fusion welding without or with preheating, controlled cooling under protective gas shield leads to thermal shock failure or porosity at the weld interface. In the present work, a filler material of(ZrB2-SiC-B4C-YAg) composite with oxidation resistance and thermal shock resistance was produced in the form of welding wire. Using the filler, gas tungsten arc welding(gTAW) was performed without employing preheating, post controlled cooling and extraneous protective gas shield to join hot pressed ZrB2-SiC(ZS), and pressureless sintered ZrB2-SiC-B4C-YAg(ZSBY) composites to themselves. The fusion welding resulted in cracking and non-uniform joining without any filler material. The weld interfaces of the composites were very clean and coherent. The Vickers micro-hardness across the weld interface was found to increase due to the increase in the volume % of both SiC and B4C in the filler material. The shear strength of the weld was about 50% of the flextural strength of the parent composite.

关键词：陶瓷基复合材料焊接界面钨极氩弧焊气体保护超高温填充材料 ZrB2 形状复杂

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