Effects of heat input on microstructure and mechanical property of Al/Ti joints by rectangular spot laser welding-brazing method

A rectangular spot laser welding–brazing method was developed to join butted Ti/Al dissimilar alloys. In order to evaluate effects of heat input on mechanical property of the joints, microstructure of the joints were characterized. TiAl₃ intermetallic compounds (IMCs) were found at the joint interface in the case of low-heat input and TiAl₃, TiAl, Ti₅Si₃, and Ti₃Al IMCs were observed at high-heat input. Results of tensile test showed that the joints fracture in the fusion zone under the condition of low-heat input and in the interfacial reaction layer or the fusion zone with a mass of porosities at high-heat input. In addition, tensile strength of specimens broken at the fusion zone is higher obviously than that at the interface or the fusion zone with a mass of porosities, and tensile strength of the joints is up to 290 MPa.     

Effect of ultrasonic vibration on thermal and material flow behavior,microstructure and mechanical properties of friction stir welded Al/Cu joints

Al/Cu dissimilar joint has been widely produced by using friction stir welding (FSW), but the weld quality remains limited. A recently developed ultrasonic     

环境湿度对A5083铝合金焊接接头力学性能及微观组织的影响

在50%、90%的湿度条件下对A5083铝合金焊接接头进行焊接,测试不同环境湿度条件下焊接接头的拉伸强度、冲击韧性、硬度以及显微组织。研究结果表明,随着湿度条件的升高,接头的抗拉强度和冲击韧性均存在整体下降的趋势,90%湿度条件下获得的焊接接头的硬度存在起伏。除了微观组织晶粒存在的长大现象外,大量的气孔产生是降低接头性能主要因素。     

Prediction and measurement of relieved residual stress by the cryogenic heat treatment for Al6061 alloy: mechanical properties and microstructure

The purpose of this study is to predict the residual stress resulting from the cryogenic heat treatment (CHT) which affects the mechanical properties and microstructure for Al6061 alloy. The CHT is very effective method to reduce the residual stress by quenching media such as liquid nitrogen, boiling water and steam. In this study, experimental T6 and CHT are carried out to measure the temperature of Al parts and to determine the convective heat transfer coefficient. This coefficient is used to predict the residual stress during FE-simulation. In order to consider the relaxation of residual stress during artificial ageing, the Zener-Wert-Avrami function with elasto-plastic nonlinear analysis is used in this study. The predicted residual stress is compared with the measured one by X-ray diffraction (XRD) and is found to be in good agreement with results of the FE-simulation. Further, after T6 and CHT, the electrical conductivity and hardness of the Al6061 alloy are measured to estimate the mechanical properties and its microstructure such as precipitates is observed by Transmission electron microscopy (TEM). Also, the creation of precipitates during T6 and CHT are verified by XRD with component analysis. It is found that CHT affects the residual stress, mechanical properties, and precipitation of the Al 6061 alloy.     

残余应力对A5083铝合金焊接接头力学性能及微观组织的影响

对A5083铝合金焊接接头进行抛丸处理,测试抛丸前后焊接接头的表面残余应力,并对焊接接头的硬度、拉伸强度、冲击强度以及微观组织进行了分析研究。研究结果表明,经抛丸后,工件表面形成压应力层。不同接头型式的表面残余应力值都明显下降。抛丸后,硬度、拉伸强度和显微组织变化不大,没有特定规律。抛丸处理的影响深度一般不超过0.3 mm,表面压应力层对内部的组织及机械性能没有显著影响。抛丸对A5083铝合金焊接接头的断裂行为没有大的影响,因此可以将抛丸处理作为一种有效的残余应力降低或者消除工艺在高速列车上使用。     

Evaluation on microstructure and mechanical properties of high-strength low-alloy steel joints with oscillating arc narrow gap GMA welding

Abstract with the purpose of improving weld joint quality and productivity, the oscillating arc narrow gap gas metal arc (GMA) welding was employed in welding quenched and tempered high-strength low-alloy thick steel. The microstructure and mechanical properties of weld joints were evaluated, namely micro-hardness, tensile strength, and low-temperature impact toughness. The test results indicated that mechanical properties of weld joints with oscillating arc narrow gap GMA welding were excellent and found to meet stipulated requirements. Oscillating arc narrow gap GMA welding is a promising process for welding quenched and tempered HSLA thick steels due to the low energy input and narrow square-butt groove.     

Effects of temper condition and post weld heat treatment on the microstructure and mechanical properties of friction stir butt-welded AA7075 Al alloy plates

In this study, AA7075-O and AA7075-T6 Al alloy plates were friction stir butt welded using two sets of weld parameters in order to investigate the effects of temper condition prior to joining and post weld heat treatment on microstructure and mechanical properties of the joints. Another goal of the work is to determine the possibility of restoring the loss of strength in the joint area experienced in welding of this alloy in the age-hardened condition by subsequent heat treatment. The study revealed that the friction stir welding resulted in a strength undermatching when the alloy joined in T6 condition while a significant strength overmatching was obtained in the joints produced in O temper condition. The post weld heat treatment led to a significant recovery in the strength of the joints produced in T6 condition, thus a significant increase in the joint performance. On the other hand, it led to a decrease in the joint performance value of the joints produced in O temper condition although the strength was increased. Furthermore, the post weld heat treatment resulted in abnormal grain growth in the joint area the degree of which depends on weld parameters used and the prior temper condition.     

Effect of pulsed magnetic field on the grain refinement and mechanical properties of 6063 aluminum alloy by direct chill casting

This paper presents different analyses by cooperation of multimobile micromanipulation systems (M⁴S) for robotic microassembly where assembly is performed in a grid pattern by dividing it into different zones. To cater this need, a new design of M⁴S for robotic assembly is proposed where different peg-in-hole assemblies are carried out. For attempting the different combinations by cooperation of M⁴S, a novel algorithm is developed which provides a solution for robotic microassembly in a more efficient and precise manner within less time. Experientially, it is proved that this novel design of M⁴S is capable of performing the different manipulation tasks of miniature parts. Different analyses prove its potentiality of robotic assembly in industrial applications.     

ASTM A487-4B材料大截面试块机械性能研究及应用

按照API规范生产泥浆泵曲轴铸件,必须进行大截面试块机械性能的材料评定。通过优化化学成分,介绍采用钢包底吹氩精炼方式,不断调整热处理工艺。特别是亚温淬火的实施。保证了材料评定要求的机械性能。     

Influence of CNTs addition on the mechanical,microstructural, and corrosion properties of Al alloy using spark plasma sintering technique

The International Journal of Advanced Manufacturing Technology - Monolithic aluminium 1000 alloy is used in overhead transmission conductors because of its light weight, high electrical...     

Effect of tilted plate vibration on solidification and microstructural and mechanical properties of semisolid cast and heat-treated A356 Al alloy

To optimize the machining process, finding the minimum uncut chip thickness is of paramount importance in micro-scale machining. However, strong dependency of the minimum uncut chip thickness to the tool geometry, workpiece material, tool-work friction, and process condition makes its evaluation complicated. The paper focuses on determination of the minimum uncut chip thickness experimentally during micro-end milling of titanium alloy Ti-6Al-4V with respect to influences of cutting parameters and lubricating systems. Experiments were carried out on a CNC machining center Kern Evo with two flute end mills of 0.8 and 2 mm diameters being used in the tests for micro- and macro-milling, respectively. It was found that the micro-milling caused more size effect than macro-milling due to higher surface micro-hardness and specific cutting forces. The specific cutting force depended strongly on feed rate (f _z) and lubricating system, followed by depth of cut (a _p) and cutting speed (v _c), mainly in the micro-scale. All output parameters were inversely proportional to the specific cutting force. Finally, depending on different process parameters during micro-milling of Ti-6Al-4V, the minimum uncut chip thickness was found to vary between 0.15 and 0.49 of the tool edge radius.     

Experimental study of microstructure,mechanical and tribological properties of cBN particulates SS316 alloy based MMCs fabricated by DMLS technique

Direct metal laser sintering process (DMLS) was chosen to develop cBN particulates reinforced SS316 based Metal matrix composite (MMC) with 5 %, 7.5 % and 10 % cBN in the nitrogen gas atmosphere using continuous wave fibre laser of 400 W output capacity. Effects of process parameters such as laser power, beam scanning speed and the mixing ratio of powder on different physical properties of the developed MMC were investigated. It was found that the physical and mechanical properties such as friction and wear behavior, micro hardness and density come up with improved results. FESEM images indicate the microstructure of the composite and evidently confirms the presence of cubic boron nitride in the SS316 matrix where chromium nitride acted as a binder in the presence of nitrogen atmosphere. The Vickers hardness values of the developed MMCs with laser power 60 W and 65 W were found in the range of 276-478 HV_0.2 and 297-460 HV_0.2, respectively. It was found that Vickers hardness is directly proportional to the % of cBN in the powder mixture and the laser beam power. The wear resistance of the sintered MMCs increased with increasing cBN content in powder mixture and results show that wear of MMCs are much lower than that of SS316. X-Ray diffraction (XRD) analysis of the fabricated MMC confirms the presence of different phases such as cBN, CrN, CrB₂, Cr₂N and Fe₃N as a consequence of a series of chemical reaction between cBN and different elements of SS316 in nitrogen atmosphere.     

Effect of different calcium contents on the microstructure and mechanical properties of Mg‐5Al‐1Bi‐0.3Mn magnesium alloy

The effect of different Ca contents on the microstructure and mechanical properties of Mg‐5Al‐1Bi‐0.3Mn (AMB501) magnesium alloys was investigated by conventional melting and casting technique using different Ca contents (1.0, 2.0, and 3.0 wt %). Increasing the Ca content resulted in higher hardness and yield strength, but decreased elongation. The improved tensile properties of the AM50‐1Bi‐xCa alloys were due to the changes in AMB501 alloy microstructure when the Ca content increased, as demonstrated by scanning electron microscope, energy dispersive spectrum, and X‐ray diffractometer. The alloy microstructure indicated that the amount of β‐Mg₁₇Al₁₂ phase on grain boundaries decreased and the morphology of β‐Mg₁₇Al₁₂ phase on grain boundaries changed from quasicontinuous‐net shape to dispersed particles. The Mg₁₇Al₁₂ phase disappeared and a new secondary phase Al₂Ca appeared after a 3.0 wt % Ca addition. Microsc. Res. Tech. 78:65–69, 2015. © 2014 Wiley Periodicals, Inc.     

Effect of the casting temperature on temperature field and microstructure of A2017 alloy during an innovative continuous semisolid rolling process with a vibrating sloping plate device

In this paper, the effect of temperature field on microstructure of A2017 alloy during an innovative continuous semisolid rolling process with a vibrating sloping plate device was studied. The results show that the alloy temperature decreases gradually from the entrance to the exit of the roll gap. In the backward slip zone, the isothermal lines have twice buckling. In the forward slip zone, the isothermal lines have once buckling. Semisolid region moves forward from the filling mouth to the exit of the roll gap with the increment of casting temperature, and the solid fraction increases from the entrance to the exit of the roll gap. The average grain size of the product increases with the increment of casting temperature, and the plastic deformation along the rolling direction happened obviously. According to the simulation and experiment, the proper casting temperature between 650 and 680 °C is suggested. A2017 alloy strip with good surface quality was obtained. The microstructure of the product is mainly composed of fine spherical or rosette grains which were elongated along rolling direction.     

Effect of gravity field,initial stress and rotation on the S-waves propagation in a non-homogeneous anisotropic medium with magnetic field

In this paper, we investigated the propagation of shear wave under the influences of the magnetic field, gravitational field, rotation and initially stressed in anisotropic non-homogeneous incompressible elastic medium. It is well known in the literature that the earth medium is not at all initial stress free and homogeneous throughout, but it is initially stressed and non-homogeneous. The frequency equation that determines the velocity of the shear waves has been obtained. Keeping these things in mind, we have discussed the frequency equation in an initially stressed, non-homogeneous medium with gravity field, magnetic field, and rotation. It has been observed that the inhomogeneity parameter, gravity field, magnetic field, and the initial stress play an important role in the propagation of S-waves propagation. The numerical values on the dimensionless phase velocities are calculated and presented graphically to illustrate the dependences upon gravity field, initial stress, magnetic field, anisotropy and rotation comparatively. The results indicate that the effects of gravity field, initial stress, magnetic field, anisotropy, and rotation are very pronounced.