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1.
Zouhair Boukha José María Sánchez-Amaya Leandro González-Rovira Eloy Del Rio Ginesa Blanco Javier Botana 《Metallurgical and Materials Transactions A》2013,44(13):5711-5723
In this study, AA5083 samples were butt welded under a conduction regime with high-power diode laser (HPDL). Various mixtures composed of Ar and CO2 were used as a shielding gas. The influence of the shielding gas composition on the microstructure and on the properties of laser welds was analyzed. The weld beads were deeply characterized by metallographic/microstructural studies, X-ray diffraction (XRD), X-ray energy dispersive spectrometry (X-EDS) chemical analyses, X-ray photoelectron spectra (XPS), microhardness, and tensile strength. The corrosion resistance of laser-remelted surfaces with different CO2/Ar ratios was also estimated by means of electrochemical tests. The addition of CO2 to the shielding gas results in a better weld penetration and oxidizes the weld pool surface. This addition also promotes the migration of Mg toward the surface of weld beads and induces the formation of magnesium aluminates spinel on the welds. The best corrosion resistance result is achieved with 20 pct CO2. The overall results indicate that the addition of small percentage of CO2 to Ar leads to improvements of the mechanical and corrosion properties of the aluminum welds. 相似文献
2.
P. Bala Srinivasan 《国际钢铁研究》2008,79(10):806-808
Laser welding of AISI 410 martensitic stainless steel was attempted in a diffusion cooled RF excited CO2 slab laser under Gaussian mode with argon and nitrogen as shielding gas. The effect of shielding gas and energy density on the resultant weld bead geometry, microstructure and hardness were assessed and discussed. It has been observed that welds obtained under nitrogen shielding conditions had higher and uniform hardness across the weld metal on account of reduced ferrite content. 相似文献
3.
Abdel-Monem El-Batahgy 《国际钢铁研究》1997,68(12):546-551
The weldability of Zn-coated steel sheets 0.7 mm thick was investigated using resistance spot welding process. The effect of welding current, welding time and holding time on weld nugget characteristics, microstructure, and mechanical properties was discussed. Then, the possibility of replacing this welding process with laser beam welding was outlined. In this respect, quality of weld joints as a function of zinc removal by grinding prior to welding was evaluated. It is found that resistance spot welding current and time are the most significant parameters in affecting both expulsion and Zn-induced porosity. Expulsion was avoided and Zn-induced porosity was reduced with the decrease in welding current and/or welding time. Zn-induced porosity was completely eliminated by zinc-removal by grinding prior to welding. The best weld joint concerning nugget characteristics, soundness and tensile shear strength was obtained using welding current of 10 kA, weld cycle of 20, holding cycle of 18. Unlike resistance spot welds, high quality of CO2 laser welds free from Zn-induced porosity could be made without zinc removal by grinding before welding. 相似文献
4.
This article discusses the effects of laser welding parameters such as power, welding speed, and focus position on the weld
bead profile, microstructure, pseudo-elasticity (PE), and shape memory effect (SME) of NiTi foil with thickness of 250 μm using 100W CW fiber laser. The parameter settings to produce the NiTi welds for analysis in this article were chosen from
a fractional factorial design to ensure the welds produced were free of any apparent defect. The welds obtained were mainly
of cellular dendrites with grain sizes ranging from 2.5 to 4.8 μm at the weld centerline. A small amount of Ni3Ti was found in the welds. The onset of transformation temperatures (A
s
and M
s
) of the NiTi welds shifted to the negative side as compared to the as-received NiTi alloy. Ultimate tensile stress of the
NiTi welds was comparable to the as-received NiTi alloy, but a little reduction in the pseudo-elastic property was noted.
Full penetration welds with desirable weld bead profiles and mechanical properties were successfully obtained in this study. 相似文献
5.
Gandham Phanikumar Sambandam Manjini Pradip Dutta Kamanio Chattopadhyay Jyotirmoy Mazumder 《Metallurgical and Materials Transactions A》2005,36(8):2137-2147
Continuous CO2 laser welding of an Fe-Cu dissimilar couple in a butt-weld geometry at different process conditions is studied. The process
conditions are varied to identify and characterize the microstructural features that are independent of the welding mode.
The study presents a characterization of the microstructure and mechanical properties of the welds. Detailed microstructural
analysis of the weld/base-metal interface shows features that are different on the two sides of the weld. The iron side can
grow into the weld with a local change in length scale, whereas the interface on the copper side indicates a barrier to growth.
The interface is jagged, and a banded microstructure consisting of iron-rich layers could be observed next to the weld/Cu
interface. The observations suggest that solidification initiates inside the melt, where iron and copper are mixed due to
convective flow. The transmission electron microscopy (TEM) of the weld region also indicates the occasional presence of droplets
of iron and copper. The microstructural observations are rationalized using arguments drawn from a thermodynamic analysis
of the Fe-Cu system. 相似文献
6.
Mei Yang Yang Liu Junlei Zhang Dong Xiang Zhimin Zhou Dan Wang Wei Liu Tingyu Huang 《Transactions of the Indian Institute of Metals》2018,71(10):2487-2496
In this work, hybrid laser-arc welding process was applied to X90 pipeline steel which has wide potential applications in the future pipeline project. The effect of different laser power (1.0, 1.5 and 2.5 kW) on microstructure and mechanical properties of weld joints was investigated. It has been found that a macroscopic morphology of “wine cup like” is observed in the weld joint with increasing laser power, where fusion zone (FZ) and heat-affected zone (HAZ) can be clearly identified. The FZ microstructure mainly includes massive ferrite, acicular ferrite (AF), and increased laser power resulting in a decrease in AF content. The HAZ consists of coarse-grained HAZ (CGHAZ), fine-grained HAZ (FGHAZ) and mixed-grained HAZ (MGHAZ). The hardness ranging from the weld center to base metal decreases and then increases, and the effect of laser power on hardness is not significant. The increased laser power leads to an evident decrease in the ultimate tensile strength and impact toughness of weld joint. The highest ultimate tensile strength and impact energy are 815 MPa, 239.1 J respectively at a laser power of 1.0 kW. A number of inclusions are observed at the bottom of dimples, which may be the (Ti,Mn)2O3 particles. 相似文献
7.
Ferritic steels are often used in thick-plate form. The feasibility of electron-beam welding such thick plates and the mechanical
properties of these welds were examined in a recent study. In this investigation, the microstructures of these thick-plate,
electron-beam welds were evaluated. The study was carried out on a 3Cr-1.5Mo-0.1V steel. Weld simulations were used to aid
in the study of the heat-affected zone (HAZ) microstructure. Such simulations allowed for a more reliable and detailed evaluation
of the variation in microstructure with distance from the fusion line. The structures were related to microhardness measurements
made across the width of the weld and the HAZ. The fusion zone and the immediately adjacent HAZ consisted of bainite platelets
with narrow films of retained austenite at many of the bainite platelet boundaries. Farther away from the fusion zone, the
structure was a two-phase mixture of bainitic platelets and ferrite produced by heating base metal between theAc
1 and theAc
3 temperatures. Still farther from the weld, the structure consisted of tempered bainite, with the degree of tempering decreasing
with distance from the fusion line. The bainite plus ferrite region and the tempered bainite section are associated with a
soft zone in the hardness profile across the weld. A postweld heat treatment (PWHT) was found to reduce the hardnesses of
the fusion zone, HAZ, and base material to relatively uniform levels. The structure across the weld and HAZ after a PWHT is
tempered bainite except in one section of the HAZ in which tempered bainite and ferrite coexist. 相似文献
8.
CO2 laser beam welding of 6061-T6 aluminum alloy thin plate 总被引:1,自引:0,他引:1
Akio Hirose Kojiro F. Kobayashi Hirotaka Todaka 《Metallurgical and Materials Transactions A》1997,28(12):2657-2662
Laser beam welding is an attractive welding process for age-hardened aluminum alloys, because its low heat input minimizes
the width of weld fusion and heat-affected zones (HAZs). In the present work, 1-mm-thick age-hardened Al-Mg-Si alloy, 6061-T6,
plates were welded with full penetration using a 2.5-kW CO2 laser. Fractions of porosity in the fusion zones were less than 0.05 pct in bead-on-plate welding and less than 0.2 pct in
butt welding with polishing the groove surface before welding. The width of a softened region in the-laser beam welds was
less than 1/4 times that of a tungsten inert gas (TIG) weld. The softened region is caused by reversion of strengthening β″
(Mg2Si) precipitates due to weld heat input. The hardness values of the softened region in the laser beam welds were almost fully
recovered to that of the base metal after an artificial aging treatment at 448 K for 28.8 ks without solution annealing, whereas
those in the TIG weld were not recovered in a partly reverted region. Both the bead-on-plate weld and the butt weld after
the postweld artificial aging treatment had almost equivalent tensile strengths to that of the base plate. 相似文献
9.
Christian B. Fuller Murray W. Mahoney 《Metallurgical and Materials Transactions A》2006,37(12):3605-3615
Friction stir processing (FSP) is used locally to modify the microstructure and thus mechanical properties of 5083-H321/5356
aluminum gas metal arc welds (GMAWs). Four specimen approaches were examined: as-arc welded, weld toe FSP (with arc weld on
either the advancing or the retreating side of tool), and weld crown FSP. Microstructures within the fine-grained FSP region
contained smaller constituent particles. Mg2Si and Al6(Fe,Mn), than those particles found in the arc weld nugget, heat-affected zone (HAZ), and base-metal (BM) locations. The FSP
improved the monotonic tensile strength, yield strength, and elongation of 5083-H321/5356 Al arc welds by 6 to 9 pct, 7 to
13 pct, and 46 to 80 pct, respectively. The addition of FSP produced a 30 pct increase in the load necessary to reach 107 cycles during four-point bending fatigue. An analysis of strengthening mechanisms determined that solid-solution, grain-size,
and precipitation strengthening made contributions to the calculated yield strength of the BM, are weld nugget, and FSP regions.
In addition, the strength mechanism analysis demonstrated that FSP increased the amount of grain-size strengthening and precipitate
strengthening by nearly 110 MPa, when compared to the arc weld nugget. 相似文献
10.
M. Arivarasu P. Roshith R. Padmanaban S. Thirumalini K. V. Phani Prabhakar G. Padmanabham 《Canadian Metallurgical Quarterly》2017,56(2):232-244
In the research work, an attempt is made to join nickel-based alloy 825 by employing CO2 laser beam welding. Successful full penetration weld joint of a 5?mm thick plate is achieved with a very low heat input of 120?J-mm?1. Narrow weld bead width of 0.6?mm at the root and 1.6?mm at the cap is observed fusion zone; the interface and base metal microstructures have been examined using both optical and scanning electron microscopic techniques to understand the microstructural changes which have occurred due to laser welding. A range of tests of Vickers micro hardness, tensile and impact tests had been performed on the weldment to ascertain the mechanical properties of the joint. Tensile failure at the base metal and a 180° root bend test conducted on the weldment ascertain the soundness of the weld joint produced. An attempt is made to correlate the microstructure and mechanical properties of the weldment. Intermetallics TiN and Al4C3 observed in the SEM\EDS analysis at the fusion zone are found to have improved the weld metal strength and hardness. 相似文献
11.
The microstructure and the mechanical properties were studied in bead-on-plate welds in a Ti-6Al-2V-1Mo alloy. The heat affected
zone (HAZ) and the fusion zone (FZ) consisted of very large primaryβ grains with theβ-phase transformed to martensite. A special bead-on-plate welding technique allowed independent measurement of the mechanical
properties of the HAZ and the FZ. Compared to the as-received (AR) material, the strength and ductility decreased in the weld.
The highest fatigue strength was found for the AR material followed by the HAZ and the FZ, whereas the ranking for fatigue
crack growth was opposite. 相似文献
12.
N. D. Raath D. Norman I. McGregor S. Hepple R. Dashwood D. J. Hughes 《Metallurgical and Materials Transactions A》2018,49(5):1536-1551
Boron steel, classed as an ultra high-strength steel (UHSS), has been utilized in anti-intrusion systems in automobiles, providing high strength and weight-saving potential through gage reduction. UHSS spot welds exhibit unique hardness distributions, with a hard nugget and outlying base material, but with a soft heat-affected zone in-between these regions. This soft zone reduces the strength of the weld and makes it susceptible to failure. Due to the interaction of various weld zones that occurs during loading, there is a need to characterize the loading response of the weld for accurate failure predictions. The loading response of certain weld zones, as well as failure loci, was obtained through physical simulation of the welding process. The results showed a significant difference in mechanical behavior through the weld length. An important result is that instrumented indentation was shown to be a valid, quantitative method for verifying the accuracy with which weld microstructure has been recreated with regard to the target weld microstructure. 相似文献
13.
Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel 总被引:1,自引:0,他引:1
The microstructure analysis and mechanical properties evaluation of laser beam welded AISI 409M ferritic stainless steel joints are investigated. Single pass autogeneous welds free of volumetric defects were produced at a welding speed of 3000 mm/min. The joints were subjected to optical microscope, scanning electron fractographe, microhardness, transverse and longitudinal tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the base metal were changed into dendritic grains as a result of rapid solidification of laser beam welds. Tensile testing indicates overmatching of the weld metal is relative to the base metal. The joints also exhibited acceptable impact toughness and bend strength properties. 相似文献
14.
Heat transfer during Nd: Yag pulsed laser welding and its effect on solidification structure of austenitic stainless steels 总被引:2,自引:0,他引:2
T. Zacharia S. A. David J. M. Vitek T. Debroy 《Metallurgical and Materials Transactions A》1989,20(5):957-967
Theoretical and experimental investigations were carried out to determine the effect of process parameters on weld metal microstructures
of austenitic stainless steels during pulsed laser welding. Laser welds made on four austenitic stainless steels at different
power levels and scanning speeds were considered. A transient heat transfer model that takes into account fluid flow in the
weld pool was employed to simulate thermal cycles and cooling rates experienced by the material under various welding conditions.
The weld metal thermal cycles and cooling rates are related to features of the solidification structure. For the conditions
investigated, the observed fusion zone structure ranged from duplex austenite (γ)+ferrite (δ) to fully austenitic or fully
ferritic. Unlike welding with a continuous wave laser, pulsed laser welding results in thermal cycling from multiple melting
and solidification cycles in the fusion zone, causing significant post-solidification solid-state transformation to occur.
There was microstructural evidence of significant recrystallization in the fusion zone structure that can be explained on
the basis of the thermal cycles. The present investigation clearly demonstrated the potential of the computational model to
provide detailed information regarding the heat transfer conditions experienced during welding. 相似文献
15.
采用CO2焊接方法焊接X100管线钢,分析了不同焊接工艺下焊接接头组织和性能的变化特征。随着焊接热输入的增加,焊接接头的屈服强度和抗拉强度降低,焊缝和热影响区处的冲击吸收功呈现先增大后减小的变化趋势,而焊缝组织均以针状铁素体(AF)为主。焊接热输入为1.17 kJ/mm时,粗晶区的显微组织主要是贝氏体铁素体(BF),强韧匹配性最为优异;当热输入增加至1.91 kJ/mm时,粗晶区的组织除了BF外,还出现了粒状贝氏体(GB),强韧水平明显降低。综合考虑,可将1.17 kJ/mm作为X100管线钢CO2焊接时的最佳热输入。 相似文献
16.
Properties of friction-stir-welded 7075 T651 aluminum 总被引:17,自引:0,他引:17
M. W. Mahoney C. G. Rhodes J. G. Flintoff W. H. Bingel R. A. Spurling 《Metallurgical and Materials Transactions A》1998,29(7):1955-1964
Friction stir welding (FSW), a new welding technique invented at TWI, was used to weld 7075 T651 aluminum, an alloy considered
essentially unweldable by fusion processes. This weld process exposed the alloy to a short time, high-temperature spike, while
introducing extensive localized deformation. Studies were performed on these solid-state welds to determine mechanical properties
both in the longitudinal direction, i.e., within the weld nugget, and, more conventionally, transverse to the weld direction. Because of the unique weld procedure,
a fully recrystallized fine grain weld nugget was developed. In addition, proximate to the nugget, both a thermomechanically
affected zone (TMAZ) and heat affected zone (HAZ) were created. During welding, temperatures remained below the melting point
and, as such, no cast or resolidification microstructure was developed. However, within the weld nugget, a banded microstructure
that influences room-temperature fracture behavior was created. In the as-welded condition, weld nugget strength decreased,
while ductility remained high. A low-temperature aging treatment failed to fully restore T651 strength and significantly reduced
tensile ductility. Samples tested transverse to the weld direction failed in the HAZ, where coarsened precipitates caused
localized softening. Subsequent low-temperature aging further reduced average strain to failure without affecting strength.
Although reductions in strength and ductility were observed, in comparison to other weld processes, FSW offers considerable
potential for welding 7075 T651 aluminum. 相似文献
17.
18.
19.
汽车轻量化后对安全性和碰撞吸能性提出了更高要求,从而促进了高强、吸能材料及其拼接技术的发展。以汽车安保件之一的汽车B柱为研究对象,采用能满足要求的DP980双相钢和22MnB5热冲压成型钢异种材料进行激光拼焊,研究焊接热输入对焊接接头显微组织与力学性能的影响。通过保持激光输出功率不变(1.3 kW)改变焊接速度的方法控制焊接热输入,考察焊接热输入与拼焊接头组织和力学性能之间的关系。利用光学显微镜、扫描电子显微镜、显微硬度测试仪和拉伸试验机研究接头不同亚区的组织和性能。结果表明,当焊接速度为16~26 mm/s时,均获得了完整而无缺陷的熔化区组织;随着焊接速度的提高,不仅焊缝表面凹陷逐步改善,并且焊接热影响区宽度也随之减小。硬度测试表明,接头中存在明显的软化区域,主要分布在DP980侧热影响区的回火区和不完全相变区,而DP980侧热影响区的细晶区、粗晶区、22MnB5侧热影响区以及焊缝金属区的硬度则有所增加,形成了焊接接头的硬化区。拼焊接头在能形成完整接头的条件下抗拉强度保持为576~597 MPa,断裂均发生在22MnB5侧的母材区,断裂时有明显的颈缩现象;接头断后伸长率为11.9%~15.5%,介于DP980母材(11%)和22MnB5(22%)母材的断后伸长率之间;研究还表明,焊接热输入越大,焊接接头相同区域的组织越粗大。 相似文献
20.
The effects of process variables on pulsed Nd:YAG laser spot welds: Part I. AISI 409 stainless steel
The weldabilities of AA 1100 aluminum and AISI 409 stainless steel by the pulsed Nd:YAG laser welding process have been examined
experimentally and compared. The effects of Nd:YAG laser welding parameters, including laser pulse time and power intensity,
and material-dependent variables, such as absorptivity and thermophysical properties, on laser spot-weld characteristics,
such as weld diameter, penetration, melt area, melting ratio, porosity, and sur-face cratering, have been studied experimentally.
The results of this work are reported in two parts. In Part I, the weldability of AISI 409 stainless steel by the pulse laser
welding process is reported. In Part II, the weldability of A A 1100 aluminum under the same operating con-ditions is reported
and compared to those of the stainless steel. When welding AISI 409 stainless steel, weld pool shapes were found to be influenced
most by the power intensity of the laser beam and to a lesser extent by the pulse duration. Conduction mode welding, keyhole
mode welding, and drilling were observed. Conduction mode welds were produced when power in-tensities between 0.7 and 4 GW/m2 were used. The initial transient in weld pool development occurred in the first 4 ms of the laser pulse. Following this,
steady-state conditions existed and conduction mode welds with aspect ratios (depth/width) of about 0.4 were produced. Keyhole
mode welds were observed at power intensities greater than 4 GW/m2. Penetration of these keyhole mode welds increased with increases in both power intensity and pulse time. The major weld
defects observed in the stainless steel spot welds were cratering and large-occluded gas pores. Significant metal loss due
to spatter was measured during the initial 2 ms of keyhole mode welds. With increasing power intensity, there was an increased
propensity for occluded gas pores near the bottom of the keyhole mode welds.
Formerly Graduate Student. 相似文献