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Improvement of microstructure and corrosion properties of friction stir welded AA5754 by adding Zn interlayer  [PDF]
Ali Shamsipur,Amir Anvari,Ahmad Keyvani
- , 2018, DOI: https://doi.org/10.1007/s12613-018-1646-z
Abstract: This study investigated the effect of Zn foil layers on the microstructure and corrosion characteristics of friction stir welded aluminum alloy 5754. Samples of various joints were prepared by applying different rotational and welding speeds, and their microstructures were evaluated via a metallographic technique and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy elemental analysis. The anticorrosion behavior of joints in the absence and presence of a Zn interlayer was studied by cyclic potentiodynamic polarization test in 3.5wt% NaCl aqueous solution, and sound welds were obtained in the presence of the Zn interlayer foil. The results revealed that the joint made at a rotational speed of 800 r/min and traveling speed of 15 mm/min achieved a chemical composition identical to that of aluminum alloy 7xxx series, and as such, it showed the best resistance to corrosion.
Corrosion behaviour of the welded steel sheets used in automotive industry  [PDF]
D. Katundi,A. Tosun-Bayraktar,E. Bayraktar,D. Toueix
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: of this paper is to characterise the corrosion resistance in the steel sheets (Hot dip galvanizing of steel sheets) used in automotive industry. In fact, corrosion of automotive components by road salt is a widely known problem. The different parts under the car body and the interior surface of body panels suffer easily from the corrosive products deposited on roads and used mainly to melt snow. A comparison in a chemical investigation of the corrosion rate for base metals (without welding) and welded steel is required. Therefore, conformity will be accomplished between the corrosion phenomena in simulated corrosion tests and those in actual cars.Design/methodology/approach: Simulated corrosion tests, wet/humidity test and hot dust/dry cycle talk test carried on in laboratory conditions was investigated quantitatively. Dynamic behaviour of the corroded specimens have been tested dynamically to simulate under the crash test conditions.Findings: Studies carried out on the vast corroded samples have shown that the pitting corrosion damage and crack initiation sites have began and propagated generally in the HAZ in the welded steel sheets (Tailored welded blanks - TWB).Research limitations/implications: This paper contains partially results of a common research project. Some limitations exist in application of hot dust/dry cycle talk to the real open air test conditions. All of these results were carried out in the laboratory conditions.Practical implications: The problem is of extreme importance to all academic, scientific, manufacturing, maintenance and industrial societies. The outcome of the proposed study will contribute to the industrial application of ARCELOR-MITTAL. The proposed study will be benefit not only for the car industry and steel makers, but also important for the other industrial applications. The proposed research can be employed in a broad range of applications in oil and natural gas industries. This project will promote multidisciplinary research and cooperation between university and industry.Originality/value: An effective corrosion test proposed by Volvo was applied to the welded sheets (TWB) in an enclosed climatic chamber. This test is a practical and inexpensive test. Impact tensile-crash test makes it possible to analyse the corrosion damage of sheet metals under the dynamic rupture.
Toughness of welded stainless steels sheets for automotive industry  [PDF]
E. Bayraktar,D. Katundi,B.S. Yilbas,J. Claeys
Journal of Achievements in Materials and Manufacturing Engineering , 2011,
Abstract: Purpose: In the automotive industry, more and more it is compulsory to develop new grades of stainless steels, such as high resistant Martensitic Stainless Steels (MA-SS) and Ferritic Stainless Steels (FSS) in order to realise certain or many complex deep drawn pieces. For these grades, resistance spot welding (RSW) is the most widespread process used largely for many parts of the car body in the automotive industry. This paper aims to characterise mechanical behaviour (toughness) of the different steel grades under dynamic test conditions.Design/methodology/approach: A special crash test device is used in different temperatures and the simulated crash tests are performed at a constant speed of 5.52 m/s.Findings: The specimen is submitted to impact tensile test at different temperatures. According to testing temperature, fracture mode varies: At low temperatures, brittle fracture occurs: due to stress concentration, fracture always occurs in the notched section. At high temperatures, the specimen fails by ductile fracture. Toughness of the steel sheets (base metals, BM or welded parts) is well compared at different materials and test conditions.Research limitations/implications: Evaluation of welded thin sheets submitted to the dynamic loading in order to correlate in real service conditions in order to realize a useful correlation between the transition temperature and deep drawability can be used for evaluating of the welding conditions and also of the material characteristics. For detail study, this type of the test needs a standard formulation.Practical implications: This is a new conception of specimen and of the impact/crash machine. It is widely used in automotive industry for practical and economic reason to give rapid answers to designer and also steel makers for ranking the materials.Originality/value: New developed test called impact crash test for evaluating the toughness of thin welded joints (tailored blanks) / mechanical assemblies in high formability steel sheets for stamping submitted to dynamic loads such as experienced in real crash tests.
Microstructure, mechanical properties and corrosion of friction stir welded 6061 Aluminum Alloy  [PDF]
Zhitong Chen,Shengxi Li,Lloyd H. Hihara
Physics , 2015,
Abstract: The microstructure, mechanical properties, and corrosion behavior of friction stir welded (FSW) AA6061 aluminum alloys were investigated. Dynamic recrystallized structures were observed and grain sizes of nugget zone (NZ), thermomechanically-affected zone (TMAZ), heat-affected zone (HAZ), and base material (BM) were different. Hardness test indicated that the minimum and maximum hardness values wereobtained in the HAZ and BM, respectively. Tensile results showed that fracture occurred in the relatively weak regions in between TMAZ and HAZ. Polarization tests illustrated that the FSW process improved the corrosion resistance of AA6061-AA6061 and the HAZ had better corrosion resistance than other regions. Raman characterizations revealed that aluminum hydroxide was the main corrosion product formed on Al after immersion experiments. Intergranular attack was observed in the NZ and downside by scanning electron microscopy.
Influence of MIG/MAG Welding Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints  [PDF]
Bruno Leonardy S. Lopes, Samuel F. Rodrigues, Eden S. Silva, Gedeon S. Reis, Waldemir dos P. Martins, Juvenilson Costa Damascena, Valdemar S. Leal
Materials Sciences and Applications (MSA) , 2018, DOI: 10.4236/msa.2018.92015
Abstract: The main objective of this research is to better understand the correlation between the constituent phases presented in the super-duplex steel SAF 2507 when it is under welding process by arc shielding gas MIG-MAG (Metal Inert Gas-Metal Active Gas). Conventional short circuit transfer and derivative STT (Surface Tension Transfer) using the 2594 welding wire as a filler metal and the effects on welding power in hardness, toughness and pitting corrosion are considered here. The results showed that the welding energy (Ew) changed the α/γ-phase’s balance and occasionally formed σ-phase in ferrite grain boundaries which led to changes in hardness, toughness and pitting corrosion resistance in molten zone (MZ), heat activated zone (HAZ) and metal base regions (MB). Furthermore, the increased amount of γ-phase improved the pitting corrosion resistance index (PRENγ) mainly in the MZ. This is due to decrease of α-phase fraction and formation of coarser grains, for higher welding energy. The toughness in the MZ decreased with less formation of γ-phase, coalescence of ferritic grains and localized formation of σ-phase, raising the hardness in the HAZ when the welding energy was lower.
Slow-strain-rate stress corrosion testing of welded joints of Al-Mg alloys  [PDF]
M. Czechowski
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The purpose of this paper is to compare the stress corrodibility of the 5083 aluminium alloy with thatof the new 5059 (Alustar) alloy, MIG and FSW welded.Design/methodology/approach: Stress corrosion cracking was examined via the slow-strain-rate-testing(SSRT) according to EN ISO 7539-7. The following parameters were measured: time-to-failure, obtained max.load, strain energy (the diagram surface under the stress-elongation curve), relative elongation of the specimen,tensile stress and reduction-in-area. The tests were carried out on cylindrical notch-free specimens with diameterd = 5 mm and measured length of L0 = 50 mm. The fractures were analysed by electron scanning microscope ofPhilips XL 30 type. Tests were carrid out in air and in a 3.5% water solution of NaCl.Findings: Tests have shown that the 5059 alloy, welded by FSW, has superior strength properties compared tothe FSW 5083 alloy, along with comparable, good resistance to stress corrosion. FSW 5083 alloy joints havevery good resistance to stress corrosion - better then those made using traditional welding methods (MIG).Practical implications: Findings will allow us to find an optimal welding method of aluminium alloys whichwill ensure high strength and resistance to stress corrosion.Originality/value: Original value are received results of the stress corrosion resistance of new method frictionstir welded (FSW) Al-Mg alloys.
Modeling of the DP and TRIP microstructure in the CMnAlSi automotive steel  [PDF]
A.K. Lis,B. Gajda
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: The CMnAlSi steel is a new grade of TRIP steels with 1wt % of Al and Si. It is important to determine the usability of the CMnAlSi for production of sheets for automotive applications.Design/methodology/approach: The effect of cooling rate and austenitization temperature on phase transformations was investigated. The dilatometric experiments of the steel were done for the full austenitization temperature 1200°C, and for (α+γ) temperature ranges: 1100°C, 1000°C, 900°C and 800°C. Steel was also processed to achieve TRIP grade by continuous annealing with modeled vertical hot dip galvanizing line. The microstructures were investigated by light optical microscopy and SEM with EDX attachment. The amount of retained austenite in the obtained microstructures was investigated with X-ray diffractionFindings: There is possibility to produce “dual-phase” CMnAlSi steel grade with controlled rolling at finishing temperature below 900°C to 800°C and fast cooling. Steel CMnAlSi is well suited for production of TRIP grade via heating cycle which correspond to vertical hot dip galvanizing process.Practical implications: This steel is suitable for production of automotive applications.Originality/value: The new procedure of control rolling from the (α+γ) temperature range of CMnAlSi steel was presented.
Microstructure and corrosion resistance of the duplex steel wide-gap one-side fluxcored wire welded joints  [PDF]
J. Nowacki,P. Zaj?c
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: this paper was to determine the impact of the wide-gap welding, with increased root face gap, on structure and corrosion properties of the welded joints executed on duplex steel by one-side welding on ceramic backings.Design/methodology/approach: In the described work, experiments were conducted to welding tests for selected joints, visual examinations, non-destructive testing of welded joints, X-ray examinations, and metallographic testing of welded joints.Findings: As a result of the performed inspection, decreasing of the ferrite content with the increase of the root face gap (increase of welding heat input) was observed. The minimum measured ferrite content was not lower than 28 %, and the maximum value did not exceed 69% (the permissible range being from 25 to 70 %).Research limitations/implications: Further studies on the impact of the wide-gap welding, with increased root face gap, on structure and corrosion properties of the welded joints are required.Practical implications: The performed tests and examinations of welded joints with root face gap ranging from 6 to 10 mm were intended for extending the standard range from 2 to 6 mm.Originality/value: The experimental program verified the testing methodology, and techniques of welding of the duplex steel with the wide-gap.
Effects of the heat input in the mechanical integrity of the welding joints welded by GMAW and LBW process in Transformation Induced Plasticity steel (TRIP) used in the automotive industry
López Cortéz, Victor H.;Pérez Medina, Gladys Y.;Reyes Valdéz, Felipe A.;López, Hugo F.;
Soldagem & Inspe??o , 2010, DOI: 10.1590/S0104-92242010000300010
Abstract: in this work an advanced high strength steel (ahss) sheet of the transformation induced plasticity (trip) type currently employed in the automotive sector was welded using a gas metal arc welding (gmaw) and a co2 laser beam welding (lbw) processes. the mechanical properties of welded tensile specimens including microhardness were determined and the results were related to the exhibited microstructures. it was found that lbw lead to relatively high hardness in the fusion zone (fz) indicating that the resultant microstructure was predominantly martensite. in the heat affected zone (haz), a mixture of phases consisting of bainite and ferrite was present. similar phase mixtures were found in the haz and fusion zone (fz) of the gmaw samples. the exhibited microstructure did not result in mechanical degradation when the gmaw specimens were tested in tension as all the fractures occurred in the bm. in contrast, the region adjacent to the haz of most tensile specimens welded using lbw failed by brittle cleavage. apparently, in this region tempering effects due to heat dissipation in the lbw process promoted carbide growth and a relatively coarse microstructure. no embrittlement was found that could be associated with the development of martensite.
A New Testing Method for Lifetime Prediction of Automotive Exhaust Silencers  [PDF]
Muhammad Yasir,Gregor Mori,Helmut Wieser,Martin Schattenkirchner,Manuel Hogl
International Journal of Corrosion , 2011, DOI: 10.1155/2011/689292
Abstract: The purpose of this paper is to highlight the problems associated with daily routine corrosion tests performed in an automotive exhaust industry. Estimation of the life time of a complete system under real conditions is always uncertain and often leads to a disagreement. A new testing setup was built in which simulation of external and internal corrosion with additional thermal cycles can be performed simultaneously. Simulation of all real conditions makes this test totally versatile and unique among all the existing testing methods. All test results were investigated quantitatively and a direct comparison was made between some field systems with different mileage and total life. Conformity was accomplished between the results from corrosion tests and parts from the vehicles. Studies carried out on the silencers have shown that the new component testing method could be used for life time estimation of parts having different material and design combinations. On the basis of obtained results it can be stated that the new testing setup can be applied for different materials and design rankings. 1. Introduction Corrosion is one of the biggest problems due to which automotive exhaust components have a limited lifetime. A very high rate of corrosion in automotive exhaust components more likely in mufflers is one of the biggest problems that automotive industry is facing since long time ago. A large variety of exhaust silencers having different design characteristics are available in an automotive market. They can be divided into various types like clamshell mufflers, wrapped mufflers, deep drawn mufflers, lock seam mufflers, welded mufflers, and so forth. Like the variety of designs, the use of different grade materials is also quite often. In the past, the predominantly used materials for exhaust muffler applications were aluminised mild steels. Later on, they were replaced by the materials of high corrosion resistance, such as stainless steels and aluminised stainless steels [1–8]. The use of ferritic chromium stainless steels, ferritic chromium-molybdenum stainless steels, and austenitic stainless steels are most common nowadays. Even stainless steels do not possess unlimited corrosion resistance due to aggressive operating conditions. The amount of extremely corroded parts is very high due to a variety of corrosion phenomenon which occurs in the field. The position of a muffler is in a rear part of an exhaust system. It is considered as a colder part of the exhaust system as compared to the parts near to an engine. An exhaust muffler is a complex assembly
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