An insight into microstructural heterogeneities formation between weld subregions of laser welded copper to stainless steel joints

The effect of laser beam welding(LBW) process on the microstructure-mechanical property relationship of a dissimilar weld between the copper(Cu) and stainless steel(SS) was investigated.Backscattered electron(BSE) based scanning electron microscopy(SEM) imaging was used to characterize the highly heterogeneous microstructural features across the LBW(Cu-SS) weld.The BSE analysis thoroughly evidenced the complex microstructures produced at dissimilar weld interfaces and fusion zone along with the compositional information.Widely different grain growths from coarse columnar grains to equiaxed ultrafine grains were also evident along the Cu-weld interface.A highresolution electron backscattered diffraction(EBSD) analysis confirmed the existence of the grain refinement mechanism at the Cu-weld interface.Both tensile and impact properties of the dissimilar weld were found to be closely aligned with the property of Cu base metal.Microhardness gradients were spatially evident in the non-homogeneous material composition zones such as fusion zone and the Cu-weld interface regions.The heterogeneous nucleation spots across the weld sub-regions were clearly identified and interlinked with their microhardness measurements for a holistic understanding of structure-property relationships of the local weld sub-regions.The findings were effectively correlated to achieve an insight into the local microstructural gradients across the weld.

Process parameters optimization for friction stir welding of RDE-40 aluminium alloy using Taguchi technique

Taguchi approach was applied to determine the most influential control factors which will yield better tensile strength of the joints of friction stir welded RDE-40 aluminium alloy. In order to evaluate the effect of process parameters such as tool rotational speed, traverse speed and axial force on tensile strength of friction stir welded RDE-40 aluminium alloy, Taguchi parametric design and optimization approach was used. Through the Taguchi parametric design approach, the optimum levels of process parameters were determined. The results indicate that the rotational speed, welding speed and axial force are the significant parameters in deciding the tensile strength of the joint. The predicted optimal value of tensile strength of friction stir welded RDE-40 aluminium alloy is 303 MPa. The results were confirmed by further experiments.

Feasibility of surface-coated friction stir welding tools to join AISI 304grade austenitic stainless steel

An attempt is made to develop the tools that are capable enough to withstand the shear, impact and thermal forces that occur during friction stir welding of stainless steels. The atmospheric plasma spray and plasma transferred arc hardfacing processes are employed to deposit refractory ceramic based composite coatings on the Inconel 738 alloy. Five different combinations of self-fluxing alloy powder and 60% ceramic reinforcement particulate mixtures are used for coating. The best friction stir welding tool selected based on tool wear analysis is used to fabricate the austenitic stainless steel joints.

Fabrication and performance evaluation of dissimilar magnesium-aluminium alloy multi-seam friction stir clad joints

This investigation is aimed to establish empirical relationships between continuous multi-seam friction stir cladding process parameters （i.e., rotational speed, welding speed and shoulder overlap ratio） and the quality characteristics （bond tensile strength, shear strength and corrosion） of dissimilar magnesiurn-aluminium alloy clad joints. The influence of considered process parameters on the clad properties was reported. Furthermore, multi-criterion optimization procedure was used to obtain ideal processing conditions, which can yield higher interface strength and lower corrosion rate of fabricated composite plate. Results indicate that, the aluminium-rich thin continuous layer, Mg-rich irregular shaped regions consists of A13Mg2 and Al12Mg17 interraetallic compounds and nature of mechanical interlocking has great influence on the joint interface strength. On the other hand, the corrosion resistance of the clad joints is greatly affected by the amount of magnesium mixed with top aluminium sheet during friction stirring. Also, bend testing shows that, the cladded joints exhibit excellent ductility.

Characteristics of friction welded AZ31B magnesium-commercial pure titanium dissimilar joints

It is essential to understand the weld interface characteristics and mechanical properties of dissimilar joints to improve its quality.This study is aimed at exploring the properties of friction welded magnesium-titanium dissimilar joint using tensile testing coupled with digital image correlation,optical and scanning electron microscopy,x-ray diffraction and microhardness measurements.Microstructurally different regions such as contact zone,dynamic recrystallized zone,thermo-mechanically affected zone,and partially deformed zone in the magnesium side were observed.No discernible regions were observed in the titanium side,as it had not undergone any significant plastic deformation.Phase analysis indicated that the aluminium from the magnesium side diffused toward the weld interface and formed a thin continuous intermetallic layer by reacting with the titanium.Microhardness mapping showed a steep hardness gradient from the titanium to magnesium side.Critical analysis is done on the tensile characteristics of the specimen and the response of the local regions to the deformation process is mapped.