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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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Microstructure and Mechanical Properties of Electron Beam Welded Joints in Different State of TC4
Taiqi Yan, Yu Wu, Xu Cheng, An Li, Shuquan Zhang
Accepted Manuscript
[Abstract](296) [FullText HTML](133) [PDF 1235KB](19)
This paper studied the influence of a specification of electron beam welding on the structure of ‘rolled+ laser deposited’ TC4 welded joints, and analyzed the mechanical properties of the joints. Results show that on the rolled side, the microstructure of heat affected zone changes obviously, the shorter the distance away from welding center, the more amount of transformed β generates, and the columnar grain gradually transforms into equiaxed grain, with the appearance of clustered martensite α'. However, on the laser-deposited side, few changes are observed in the heat affected zone, β grain stays the shape of columnar, in which martensite α' generates, no equiaxed grain generates. The change trend of microhardness on both sides is similar, the closer the distance from the center, the higher the microhardness gets, the maximum hardness is around 400HV found in the fusion zone. The mechanical properties of welding joints are similar to that of forged TC4, all the fractures locate in the laser-deposited base metal region.
Accepted Manuscript  doi: 10.12073/j.hjxb.20180320001
[Abstract](174) [FullText HTML](44) [PDF 1199KB](21)
Development of a narrow gap welding experiment system for oscillating arc sensing
Wenji Liu, Zhenyu Guan, Liangyu Li, Jianfeng Yue
Accepted Manuscript
[Abstract](196) [FullText HTML](92) [PDF 945KB](4)
In order to improve the precision and reliability of welding arc sensor in narrow gap, as well as to research the principle of arc sensor characteristic parameters influenced by the distance between welding torch and the side wall, by measuring the torch position using high precision laser displacement sensor, an experiment system for swing arc sensor which can simultaneously acquire welding voltage, welding current, welding torch swing position and arc image four signals was developed based on TMS320F2812 and Labview. Experiment was carried out by the welding method of P-GMAW. It was proved by the experiment that the established system is reliable and effective. The system has laid the necessary foundation for the further study of the characteristics of the narrow gap oscillating arc sensing.
Laser Welding of T91 Martensite Heat-resistant Steel with Feeding Wire
Xiaoyong Qi, Bing Ye, Shiwen Yu, Liang Yu
Accepted Manuscript  doi: 10.12073/j.hjxb.201940
[Abstract](257) [FullText HTML](78) [PDF 1011KB](20)
The research on laser welding 5-mm thick T91 martensite heat-resistant steel with filler wires is conducted, and the effects on weld appearance, microstructures, and porosity are studied, also the weld mechanical properties of the optimal parameter are tested. The results show that when welding heat input increased by using same material wire to weld T91 steel, weld seam width, porosity decreased, and grain size changed a little, microstructure of weld zone and HAZ are tempered martensite. The weld seam can be pore-free with the parameter of power 5 600 w, speed 1.2 m/min, feeding speed 1.2 m/min, its microhardness is 300 HV, tensile strength is 697 Mpa, no cracks appear by 180° bending and back bending, and the impact properties are better than base metal at 20/0/–20 °C.
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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Research paper
Research progress of high-entropy amorphous materials and their additive manufacturing technology
Fengyuan SHU, Sicheng NIU, Peng HE, Shaohua SUI, Xiaodong ZHANG
2021, 42(9): 1-8.   doi: 10.12073/j.hjxb.20201203001
[Abstract](0) [FullText HTML](0) [PDF 1018KB](0)
High-entropy amorphous alloys (HEAAs) exhibit unique physical, chemical and mechanical properties as well as better thermal stability. Thus, its fabrication technology has become one of the important research hotspots at home and abroad. However, high-entropy amorphous materials manufactured by traditional technology had defects such as coarse crystal grains and material waste, which was difficult to meet the needs of processing production. The precise manufacturing and rapid cooling of additive manufacturing technology could solve the problems, and produce high entropy amorphous alloys with superior properties. This review research briefly introduced the research system and common preparation methods of high-entropy amorphous materials. It mainly focused on the research about fracture strength, corrosion resistance and thermal stability of high-entropy amorphous materials. The process features and advantages of additive manufacturing technology, and the scientific difficulties for applying this technology to fabricate high-entropy amorphous alloys were summarized. The results showed that additive manufacturing technology contributed to high-entropy amorphous materials with dense and uniform microstructures, while the explanation for the formation of amorphous phases was limited to the four effects of high-entropy alloys, Finally, a discussion with two additive manufacturing methods commonly used in the fabrication of high-entropy amorphous materials in recent years was made. Furthermore, the prospects for the development trend of fabricating high-entropy amorphous materials by additive manufacturing technology were put forward.
Numerical simulation of TIG arc characteristics of hollow tungsten electrode
Zheng LEI, Zongtao ZHU, Yuanxing LI, Hui CHEN
2021, 42(9): 9-14, 27.   doi: 10.12073/j.hjxb.20210131003
[Abstract](0) [FullText HTML](0) [PDF 1446KB](0)
The numerical model of hollow tungsten TIG welding with inner diameter of 2 mm is developed. The source terms of momentum equation and energy equation and the conductivity of argon gas are loaded by the user defined function (UDF) of Fluent software. The temperature field, flow field and arc pressure are calculated when the welding current is 60 A in steady state. The results are compared with those of solid tungsten TIG arc under the same conditions. The results show that the shape of hollow tungsten TIG arc is bell jar shape, and the temperature field is concave at the top middle position due to the air flow and current density. The velocity of plasma below the tungsten pole is faster than other regions. The arc pressure is uniformly distributed, and the anode surface pressure is uniformly distributed in cylindrical shape. Compare with TIG welding under the same current condition, the maximum temperature, maximum plasma flow velocity and peak arc pressure of the hollow tungsten arc are reduced by 17.3%, 40% and 57%, respectively, and the peak temperature of the 2 mm cross section below the tungsten electrode is reduced by 27%. The weld width of surfacing welding increases by 30% but the weld depth decreases by 27.9%.
Microstructure and mechanical properties of thermal simulated MHC/GH4099 diffusion brazing joints
Hongyan CHE, Tianming ZHENG, Henglin WANG, Hao DONG, Yingjie YAN, Rui CAO
2021, 42(9): 15-20.   doi: 10.12073/j.hjxb.20210221001
[Abstract](0) [FullText HTML](0) [PDF 1163KB](0)
The molybdenum alloy (MHC) and the nickel alloy (GH4099) were successfully joined with NiCrSiB as the interlayer by the Gleeble-3800 thermal simulated machine. Microstructure of MHC/GH4099 welded joints were characterized by scanning electron microscope (SEM), energy dispersive scanning (EDS) and X-ray diffraction (XRD). The effects of bonding temperature on microstructure and shear strength were also investigated. Results indicated that a reliable welded joint can be obtained at peak temperatures of 950 ℃, 1 000 ℃ and 1 050 ℃ and holding time of 600 s. The MHC/GH4099 joints were mainly composed of γ-Ni solid solution, CrMo solid solution, MoNi and CrB, Ni3Si phase. The shear strength of the joint at 1 050 ℃ can reach 116 MPa. The larger stress concentration in the heat affected zone of MHC side was the main reason of brittle fracture for MHC/GH4099 joints.
Root crack propagation angle of load-carrying fillet weld T-joints
Yafang DU, Dongpo WANG, Xiuguo LIU, Baoming GONG, Caiyan DENG
2021, 42(9): 21-27.   doi: 10.12073/j.hjxb.20210119001
[Abstract](0) [FullText HTML](0) [PDF 1171KB](0)
Aimed at the root fatigue failure propagation path problem of T-joints in Q355B low alloy steel, an equivalent stress intensity factor (KEQ) method based on force analysis and calculation was proposed to predict the root crack propagation angle. The maximum error of solving the stress intensity factor is less than 5% verified by finite element simulation. Compared with the maximum circumferential stress method (MCS method) and the effective structural stress method (ETS method) based on finite element analysis, and combined with the bending fatigue test results of three different stress levels, it is found that: The crack propagation angles calculated by equivalent stress intensity factor method, maximum circumferential stress method and effective structural stress method are 25.6°, 25.9° and 32.2°, respectively. Compared with the root crack propagation angle of 24° in the actual fatigue test, the errors are 6.67%, 7.92% and 34.17%, respectively. The results show that KEQ method has the highest accuracy in solving crack propagation angle, which is more suitable for predicting the root crack propagation angle of T-joint fillet weld under bending fatigue loading.
Analysis of welding residual stress in multi-pass hybrid laser-MIG welded X80 pipeline steel
Chunyan YAN, Hao ZHANG, Zijiang ZHU, Kezhao ZHANG, Zhengjia GU, Baosen WANG
2021, 42(9): 28-34, 41.   doi: 10.12073/j.hjxb.20210312001
[Abstract](0) [FullText HTML](0) [PDF 1392KB](0)
Combined experimental and numerical investigation of temperature field and residual stress field of X80 pipeline steel multi-pass hybrid laser-MIG welding were performed. Influence of laser power on microstructures, temperature distribution and residual stress distribution in the hybrid welded joints were analyzed. The results show that rising maximum temperature of the molten pool and decreasing post-welding cooling rate were obtained with increasing laser power. More acicular ferrite and granular bainite, less lath bainite formed in the coarse grained heat affected zone. Overall residual stress level in the X80 pipeline steel hybrid welded joints were high with peak tensile stress occurred in the weld metal for longitudinal stress, transverse stress and through-thickness stress. In the laser power range from 2.0 to 3.5 kW, peak stress of Von Mises equivalent stress, longitudinal stress, transverse stress and through-thickness stress all decreased with increasing laser power. However, peak stress of the stresses increased with laser power increasing from 3.5 kW to 4.0 kW.
Repair process of magnesium alloy casting by He-Ar mixed gas TIG welding
Yi CHEN, Longtao GUO, Tongfu QI, Chunli YANG
2021, 42(9): 35-41.   doi: 10.12073/j.hjxb.20201223001
[Abstract](0) [FullText HTML](0) [PDF 1890KB](0)
Magnesium alloy plays an important role in weight-loss because of its high specific strength, most of magnesium alloy components are casting. The defects of magnesium alloy castings become a manufacturing bottleneck issue. The repair process of magnesium alloy castings by tungsten inert gas (TIG) welding was studied, the effects of protect gas on the form, microstructure and properties of TIG repair beads were examined. The effects of helium content on the penetrations of welding beads were analyzed through the arc shape and arc voltage of TIG welding under different helium content. The results showed that the form of the weld bead could be improved by changing the helium content, the penetration and the penetration to width ratio could be improved by increasing the helium content, with no obvious effect on the microstructure and the hardness. The results of the simulating defect repair experiments showed that, the He-Ar mixed gas TIG welding repair process could repair shallow defects of magnesium alloy castings, increasing the helium content in the protect gas could increase the penetration and the suitability of this repair process.
TiB2-based ceramics/42CrMo alloy layered gradient material mechanical test and structure design
Mingyuan LU, Baohong HAN, Wanheng HE, Zhongmin ZHAO
2021, 42(9): 42-48, 73.   doi: 10.12073/j.hjxb.20210405001
[Abstract](0) [FullText HTML](0) [PDF 1017KB](0)
Based on the previous supergravity field synthesis gradient materials, a TiB2-based ceramic /42CrMo graded material with continuous gradient content of TiB2-TiC-Fe has been preparatived. XRD, SEM, hardness test and three-point bending strength test on the materials are conducted. And electrical measuring method is used to obtain ceramic substrate part of elasticity modulus.The elastic modulus of the intermediate transition zone is fitted. Finally, an analytical method is used to calculate the stress-strain distribution of the graded material.The results show that the ceramic/alloy phase boundary changes in a continuous gradient, and the hardness decreases in a gradient from ceramic to metal. Three point bending test found that the type of material has similar to the metal plastic deformation features. Therefore, obvious failure delay behavior appears. The elastic modulus of pure ceramic is about 560 GPa. The variation form of elastic modulus in the intermediate transition zone is closer to trigonometric function. The calculated stress indicates that the damage occurs from the bottom of the metal, and then the crack spreads to the top of the ceramic, which is consistent with the experimental phenomenon of this type of material.
PBGA solder joint fatigue under temperature cycling, random vibration and combined vibration and thermal cycling loading conditions
Tong AN, Xiaoxuan CHEN, Fei QIN, Yanwei DAI, Yanpeng GONG
2021, 42(9): 49-54.   doi: 10.12073/j.hjxb.20190417001
[Abstract](0) [FullText HTML](0) [PDF 1632KB](0)
In this paper, temperature cycling, random vibration and combined loading tests were conducted on plastic ball grid array assemblies. The fatigue lives, the failure modes of the solder joints and the location of the failed solder joints for single loading and combined loading conditions were compared and analyzed. The results show much earlier solder joint failure for combined loading than that for either temperature cycling or pure vibration loading at room temperature. During temperature cycling and random vibration loading tests, the components at the central region have more failed solder joints than other components. The effect of the component location on the stresses and strains at the solder joints is not significant for combined loading. The primary failure mode is cracking within the bulk solder under temperature cycling, whereas the crack propagation path is along the intermetallic compound (IMC) layer for vibration loading. The solder joints subjected to combined loading exhibit both failure modes that occur for the temperature cycling and the vibration loading conditions.
Prediction and optimization of tensile strength of 7A52 aluminum alloy friction stir welding joints based on response surface methodology
Wenxue FAN, Furong CHEN
2021, 42(9): 55-60.   doi: 10.12073/j.hjxb.20210322001
[Abstract](0) [FullText HTML](0) [PDF 742KB](0)
In order to study the effects of welding speed, stirring head rotation speed and pressure deep of shaft shoulder on tensile strength of 7A52 aluminum alloy friction stir welding. 20 groups of tests were designed by response surface methodology based on central composite test design, and response function relationship were established. In order to verify the accuracy of the response function relationship, variance analysis and regression analysis were used to determine the dominance of the regression model, and the deviation of correlation coefficient R2 was only 3.17%. The accuracy of the model was verified by analyzing the influence of single welding parameter and double welding parameter on tensile strength. Finally, the model was verified by tensile test. The results show that the joint tensile strength can be predicated based on response function relationship of response surface methodology fitting, and the best combination of welding parameter (welding speed 110 mm/min, stirring head rotation speed 1 436 r/min, pressure deep of shaft shoulder 0.55 mm) was gained. The maximum predication tensile strength was 380 MPa.
Two-dimensional numerical simulation of boundary effect of explosive welding based on SPH method
Guanghong MIAO, Jiuying AI, Yu HU, Honghao MA, Zhaowu SHEN
2021, 42(9): 61-66.   doi: 10.12073/j.hjxb.20210203002
[Abstract](0) [FullText HTML](0) [PDF 1039KB](0)
In order to reveal the mechanism of explosive welding boundary effect, LS-DYNA software and meshless SPH method is used to carry out two-dimensional numerical simulation of explosive welding boundary effect on TA2/Q235, Q235/Q235, Q235/TA2 and 304 stainless steel/Q235 composite plates respectively in this paper. The thickness of the flyer plate is 2 mm and the thickness of the based plate is 16 mm. By observing the flight attitude of the flyer plate in different simulation groups, it revealed that the tearing of the flyer plate occurs before the collision with the base plate. When the base plate is consistent and the explosives are emulsion explosives and expanded ammonium oil mixed explosives, the tearing size of the TA2 is larger than the Q235 steel and 304 stainless steel. When the base plate and flyer plate are made of Q235 steel, the tearing size of the flyer plate under the condition of emulsion explosive is larger than that under the condition of expanded ammonium oil mixed explosive. The above results show that the boundary effect of explosive welding still exists when the flyer plate and explosive change, but the severity of the boundary effect is different. The lower the ultimate tensile strength of the flyer plate or the higher the explosive velocity, the more serious the boundary effect phenomenon.
Dynamic distribution characteristic of temperature field and weld morphology control in pulsed microplasma arc welding ultra-thin sheets
Jianping HE, Xuyang TAO, Yongfeng JI
2021, 42(9): 67-73.   doi: 10.12073/j.hjxb.20200423001
[Abstract](0) [FullText HTML](0) [PDF 1100KB](0)
Based on the numerical calculation of pulsed microplasma arc welding (P-MPAW) 100 μm ultrathin sheets, dynamic distribution characteristic of weld pool temperature field under dynamically loading the actual heat source and influence of pulse parameters on it were studied. Effect of pulse parameters on weld morphology was investigated and the numerically calculated results were verified. In addition, the relations between the matching of pulse parameters and welding speed with the weld morphology were discussed. The results were as following. Firstly, the dynamic variations of temperature distribution are characterized with cyclical fluctuation and inertia. The higher the pulse frequency or the smaller the ratio of peak current to base current, the stronger the fluctuating amplitude and the more intense the inertia of temperature variation corresponding to the changes of pulsed current are. Secondly, there are two forms of weld morphologies with pulsed current, continuous weld and non-continuous weld morphologies. These two different weld morphologies are attributed to the matching of welding speed, seam length during peak current period and pulse parameters. Finally, the continuity of experimentally obtained weld morphology was well explained by the numerically calculated results about the ratio of pulse period to lasting time when the maximum weld pool temperature is higher than the material melting point.
Large diameter hollow stud welding process based on longitudinal magnetic field control
Deku ZHANG, Siyuan HE, Hongyu YIN, Kehong WANG
2021, 42(9): 74-80.   doi: 10.12073/j.hjxb.20210514002
[Abstract](0) [FullText HTML](0) [PDF 2185KB](0)
The arc stud welding method was used to weld 45 steel plate and hollow stud with outer diameter of 20 mm and inner diameter of 10 mm. Effects of the rotating arc magnetic field on microstructure and mechanical properties were studied. The results show that with the longitudinal rotating arc magnetic field, the charge in the arc moved spirally under the action of Lorentz force, which extended outward to some extent and the appearance of the joint was improved. The thermal cycle condition of joint was improved thanks to the continuous stirring of molten pool by controlled arc, and the solidification and crystallization of molten pool was affected. The proeutectoid ferrite showed a regular network distribution and the pearlite became fine. For the decrease of joint temperature gradient, the solid-state phase transition time increased, the martensite content in the heat affected zone of the parent metal of 45 steel side decreased significantly and the width of HAZ became smaller. When the rotating arc magnetic field current was too large, the spatter tendency increased obviously as well as the porosity in the weld increased. When the welding time of 1 400 ms, the welding current of 800 A and the rotating arc current of 0.43 A, the arc was fully burned at the full end face of the hollow stud, the shear strength of joints can reach 325 MPa.
High-temperature wear resistance of Co-based cladding layers by ultra-high speed laser cladding on the surface of the cast-rolling roller sleeve
Yan YIN, Zhihui LI, Hui LI, Zhiheng LI, Chao LU, Ruihua ZHANG
2021, 42(9): 81-89.   doi: 10.12073/j.hjxb.20210122001
[Abstract](0) [FullText HTML](0) [PDF 2342KB](0)
In order to improve the service life of the cast-rolling roller sleeve, a Co-based cladding layer was prepared on the surface of the 32Cr3Mo1V cast-rolling roller sleeve using ultra-high-speed laser cladding technology. The surface morphology, microstructure, high-temperature friction and wear properties of the cladding layer were analyzed. And which was compared with that of the preferred conventional laser cladding layer. The results show that the preferred ultra-high-speed and conventional laser cladding layers all have a smooth surface and a good combination with the substrate without obvious cracks, pores and other defects. In contrast, the microstructure of the layer by ultra-high-speed laser cladding is very uniform and fine. And the dendrite axis spacing is extremely small, which largely suppresses the range of dendrite segregation. As a result, the more uniform distribution of element was obtained. During the process of 700 ℃ high temperature friction and wear test, the super oxide wear debris produced from the high-speed laser cladding layer is more smaller compared with that of conventional laser cladding layer. Therefore the agglomeration effect is more likely to occur, which is conducive to the formation of the enamel layer with anti-friction resistance. As the same time, the deformation of the layer by ultra-high-speed laser cladding is smaller, which has more effectively support for the enamel layer, consequently a large area enamel layer can be obtained. Thus the ultra-high-speed laser cladding layer exhibits excellent high-temperature friction and wear resistance.
Microstructure and wear resistance of TiB2/Ni composite coating on pure copper surface by argon arc cladding
Qiang MA, Mingxuan CHEN, Junsheng MENG, Chengshuo LI, Xiaoping SHI, Xin PENG
2021, 42(9): 90-96.   doi: 10.12073/j.hjxb.20210202002
[Abstract](0) [FullText HTML](0) [PDF 1632KB](0)
The TiB2 reinforced Ni-based composite coating is prepared on the surface of pure copper by argon arc cladding technology to improve its wear resistance. The Ti powder, B powder and Ni powder are ball-milled and mixed. The ceramic particle reinforced nickel base coating was fabricated by melting the preset powder on the surface of pure copper by using argon arc cladding. The phase of the coating and the composition, distribution and structure of ceramic particles in the coating were analyzed by X-ray diffractometer, scanning electron microscope and transmission electron microscope. The microhardness and wear properties of the coating were tested by microhardness tester and friction and wear tester. The results showed that the phases of the cladding coating mainly include γ (Ni, Cu) and TiB2. The ceramic particle reinforced phases are uniformly dispersed in the cladding coating. However, the particle phase TiB2 exists in the form of hexagon. There is no defect in the interface between cladding layer and substrate. The cladding coating has high microhardness. When the mass fraction of (Ti+B) is 10%, the microhardness of the coating is as high as 781.3 HV. Compared with the pure copper substrate, the microhardness of the cladding coating is increased by about 11.7 times. With the increase of (Ti+B) mass fraction, the friction coefficient and wear loss of the coating decrease first and then increase under the same wear conditions, respectively. The in-situ synthesized TiB2 particles reinforced nickel base coating can significantly improve the wear resistance of the pure copper surface by argon arc cladding technology.

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