Weld Nugget Hardness Research Articles

Investigation of Magnesium and Chromium Fillers FSW Dissimilar Joint of AA6063 and AA 5154

Friction stir welding (FSW) is a solid-state metal joining process. There is no melting and recasting of metal while welding is used. Some of the defects commonly encountered in FSW are tunnel defect, bond, cracks, pin holes, and pipping defects. The defects occur because of improper metal mixing and less heat input in the weld nugget zone. In the fusion welding process, a filler rod is employed to form a quality weld with superior mechanical properties. In this work magnesium and chromium powders are used as filler materials. The purpose of this study is to ascertain whether filler materials and manufacturing processes have an impact on the weld nugget zone spot weld joint formation as well as the mechanical and abrasive properties of welded joints. This study's FSW filler materials mixing ratio and process parameters were improved by using the Central Composite Design (CCD) idea, which is discussed in more detail below Response Surface Methodology (RSM). The best empirical relationship between the parameters was provided by the CCD. The mathematical relationships were established to forecast the maximum tensile strength, maximum weld nugget hardness, and minimum corrosion rate by incorporating filler materials with process parameters. The optimal processing factors combination is predicted by conducting the validation test. The optimum parameters were the tool rotatory speed 600–1000 revolution per minute, welding speed 60 to 180 mm/min, plunge depth of 0.05 to 0.25 mm, center distance between the sample is 0–4 mm, as well as powder mixing ratio of 90 : 10, 92.5 : 7.5, 95 : 5, 97.5 : 2.5, and 100 : 0, the tensile test, microhardness, and corrosion rate analysis were conducted on the weld specimen. The welded test specimen provides better joint strength, weld nugget hardness, and enhanced corrosion resistance properties. The microstructure analysis shows the fine grain structure and homogeneous distribution of filler material with the base metal in the welded area.

A fuzzy model to predict the mechanical characteristics of friction stir welded joints of aluminum alloy AA2014-T6

AbstractFriction stir welding is a prominent technique for making defect-free joints of aluminum alloys. The aluminum alloy AA2014-T6 finds wide applications in aerospace, naval and automotive applications. This paper attempts to predict the tensile strength and hardness characteristics of friction stir welded aluminum alloy AA2014-T6 by a fuzzy logic model. Friction stir welding was carried out by varying tool rotational speed (700, 1,000 and 1,400rpm), welding speed (20, 35, 50mm/min) and axial force (10, 12, 14kN) at three levels. The tensile strength and hardness characteristics of the welded specimens were obtained from the experiments conducted as per Taguchi’s L27 orthogonal array. A Mamdani-type fuzzy logic model was developed to predict the tensile strength and nugget hardness characteristics of the FSW joints. The fuzzy model was evaluated by comparing the results of confirmation experiments with that of the results predicted by the model. The confirmation experiments were conducted with a new set of parameters other than the ones used for building the model. The fuzzy model exhibits marginal variations of 2.53% for tensile strength and 2.42% for weld nugget hardness compared to the results of the conformation experiments.

Forecasting process parameters on weld nugget hardness of filler added friction stir welded dissimilar aluminium alloys 5052 And 6082 joints

This article deals with the optimization of friction stir welding process parameters with filler ratios on dissimilar Aluminium alloy groups. For this purpose, 6 series Aluminium alloy 6082 and 5 series Aluminium alloy 5052 were taken. Microhardness property was conducted under various rotational speeds, welding speed, plunge depth, Center distance between the holes and filler mixing ratio. The Central Composite Design (CCD), the most commonly used Response Surface Methodology (RSM), is considered to develop the prediction equation. A validation analysis is carried out, and the results were compared with the relative impact of input parameters on weld nugget microhardness. It is observed that the increase in welding speed with plunge depth and filler ratio result in the increase of weld nugget microhardness up to a maximum value. The maximum weld nugget hardness of fabricated joint was obtained with the welding process parameters combination of 1000 rpm rotational speed, 125 mm/min welding speed, 0.15 mm plunge depth, 2 mm centre distance between the holes, and filler ratio of 95% Mg and 5% Cr.

Optimization of friction stir welding parameters for better hardness in weld nugget of hybrid aluminium composite

This research deals with weldability analysis of hybrid aluminium composite. Varying percentage of bagasse ash (4, 8, 12 wt%) and constant wt.% of Molybdenum disulphide is used as reinforcement to developed hybrid composite. Friction stir welding process was adopted for weldability analysis. Tool rotation speed, welding speed are selected as input parameter and hardness of weld nugget was selected as output response. Taguchi method was adopted for designing experimental plan and to study the influence of input parameter over out response. Results revealed that tool rotation speed has major contribution (57.3%) on output response. ANOVA results depicts that all the input parameter has significant over output response.

A Metallurgic and Mechanical Differentiation to Friction Stir Welding (FSW)

The objective of this research was to measure the material properties as well as the forces to orthodox friction stir welding (FSW) performed in air of AA6061. These results were compared by using ultimate tensile strength (UTS) and weld root properties such as joint line residue length at the crossing point between the welded aluminum alloy which allows crack initiation. Metallurgic cross sections of the AA6061 welds were prepared and the weld nugget hardness between the welding parameters was compared as well. Experiments such as this one and others enumerating the forces and process parameters must be achieved. A steady state model of temperature distribution has been put forward and is shown to precisely forecast trends in heat input using heat generation equations from [1,2]. Temperature distribution was measured and correlated to data by use of Micron Thermal Imaging camera.

Microstructure, Mechanical and Corrosion Behaviour of AA7075 Aluminium Alloy Friction Stir Welds

Friction stir welding (FSW) is emerging as an alternative technique for joining high strength aluminium alloys as it eliminates the problems during fusion welding. In this work, the effect of post weld treatments (PWHT), viz., peak aging (T6) and retrogression and reaging (RRA) on the microstructure, mechanical properties, pitting corrosion and stress corrosion cracking (SCC) resistance of AA7075 aluminium alloy friction stir welds has been studied. An attempt also has been made to change the chemical composition of the weld nugget by adding boron carbide (B 4 C) nano powder with the aid of the FSW. Hardness and tensile properties were found to be better in PWHT – T6. Pitting corrosion and SCC resistances were improved in PWHT-RRA condition with negligible loss of strength when compared to PWHT-T6. RRA promotes coarse precipitation of the equilibrium phase η in the grains and sub grain boundaries, while maintaining a fine distribution of η' in the grain interiors. The increased strength and hardness in the peak aged (T6) condition was attributed to the presence of semi-coherent intermediate η' (MgZn 2 ). With the addition of B 4 C nano powder to the weld nugget, hardness, tensile properties, pitting corrosion resistance and SCC resistance were further improved significantly when compared to the unreinforced weld nugget. PWHT-RRA treatment on the welds with B 4 C nano powder addition resulted in improved hardness of weld nugget which is attributed to the uniform distribution of strengthening precipitates in the matrix and powder strengthening. Pitting corrosion resistance, Tensile strength and SCC resistance was improved significantly in B 4 C added welds after RRA treatment when compared to the same welds without B 4 C addition.

Mechanical Behaviour Investigation Of Aluminium Alloy Tailor Welded Blank Developed By Using Friction Stir Welding Technique

The objective on the research was to investigate the mechanical properties and microstructure of tailor welded blank (TWB) made from AA6061-T6 and AA1100 using friction stir welding (FSW) process. Due to the dissimilar mechanical properties of the two aluminium alloys, microhardness test was conducted to measure the hardness distribution across the weld nugget. The mixing of two distinct materials was influenced by tool rotation speed. Therefore, microstructure analysis was carried out to investigate the grain size and shape. The grain size of AA6061-T6 has increased in the heat affected zone (HAZ) while for AA1100 has decreased. In the weld nugget, it has found a hook defects in the dissimilar aluminium joining. By using monotonic tensile load, the different weld line direction was observed with the expansion in tool rotation. The joints failure were consistently on the area of AA1100 series. Furthermore, two specimens were investigated, one through the dissimilar aluminium and the other through similiar material. Inspection of the weld nugget hardness was shown that nonhomogen material intermixing during the stiring process as confirmed by microhardness measurement.

Similar and dissimilar resistance spot weldability of galvanised DP1000 and TWIP980 steels

ABSTRACTSimilar and dissimilar combinations of a 1000 MPa galvanised dual phase (DP) steel and a 980 MPa twining-induced plasticity (TWIP) steel were resistance spot welded under different welding parameters. The microstructure, expulsion situation, nugget size and mechanical properties of spot welds were evaluated systematically. The results showed that the differences of microstructure and chemical compositions caused that the weld nugget hardness increases in the order of TWIP/TWIP, DP/TWIP and DP/DP. The lower melting point and heat conductivity of the TWIP steel and the lower electric resistance of the zinc coat on the DP steel caused that the expulsion occurring current increased in the order of TWIP/TWIP, DP/TWIP and DP/DP and under the same welding condition the nugget diameter increased in the order of DP/DP, DP/TWIP and TWIP/TWIP. Furthermore, the tensile shear failure mode and location depends on the nugget size, microstructure and hardness distribution of spot weld.

타이타늄 소재 마찰교반용접 기술 동향

Titanium and its alloys have been widely using in the various field of industry application due to high corrosion resistant properties and mechanical properties. Titanium is highly reactive in the high temperature state and the formation of titanium oxide and porosities in the nuggets of fusion welding will results in the degradation of the mechanical properties. For this reason the studies of friction stir welding for titanium have been investigated recently. The FSW zones of titanium were classified by the weld nugget (WN), the linear transition boundary (TB) and the heat affected zone (HAZ). The WN along with titanium parent was characterized by the presence of twins and dislocations. The average grain size and hardness of WN has been changed according to heat input. The grain refinement resulted from the FSW increased the hardness in the stir zone. Sound dissimilar joints between SUS 304 and CP-Ti were achieved using an advancing speed of 50 mm/min and rotation speeds in the range of 700-1100 rpm. Aluminum 1060 and titanium alloy Ti-6Al-4V plates were lap joined by friction stir welding, hence the ultimate tensile shear strength of joint reached 100% of Al 1060. Mg alloy and Ti were successfully butt joined by inserting a probe into the Mg alloy plate with slightly offsetting. But Ti-Al intermetallic compound layers formed at the interface of these joints.

Multi-objective optimization of friction stir welding parameters using desirability approach to join Al/SiCp metal matrix composites

Silicon carbide particulate (SiCp) reinforced cast aluminium (Al) based metal matrix composites (MMCs) have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, high temperature capability and good wear resistance. Friction stir welding (FSW) process parameters play major role in deciding the performance of welded joints. The ultimate tensile strength, notch tensile strength and weld nugget hardness of friction stir butt welded joints of cast Al/SiCp MMCs (AA6061 with 20% (volume fraction) of SiCp) were investigated. The relationships between the FSW process parameters (rotational speed, welding speed and axial force) and the responses (ultimate tensile strength, notch tensile strength and weld nugget hardness) were established. The optimal welding parameters to maximize the mechanical properties were identified by using desirability approach. From this investigation, it is found that the joints fabricated with the tool rotational speed of 1370 r/min, welding speed of 88.9 mm/min, and axial force of 9.6 kN yield the maximum ultimate tensile strength, notch tensile strength and hardness of 265 MPa, 201 MPa and HV114, respectively.

Correlation between weld nugget grain size, weld nugget hardness and tensile strength of friction stir welded commercial grade aluminium alloy joints

Friction stir welding process (FSW) is an emerging solid state joining process in which the material that is being welded does not melt and recast. The FSW process and tool parameters play a major role in deciding the joint strength. Joint strength is influenced by the grain size and hardness of the weld nugget region. Hence, in this investigation an attempt was made to develop empirical relationships to predict the grain size and hardness of weld nugget of the friction stir welded AA1100 aluminium alloy joints. Linear regression relationships are established between grain size and hardness of the weld nugget and weld nugget hardness and tensile strength of FSW joints. The developed relationships can be effectively used to predict the weld nugget grain size and tensile strength of the joint non-destructively by measuring the weld nugget hardness.

Statistical analysis to predict grain size and hardness of the weld nugget of friction-stir-welded AA6061-T6 aluminium alloy joints

AA6061 aluminum alloy has gathered wide acceptance in the fabrication of light weight structures requiring high strength-to-weight ratio and good corrosion resistance. Friction-stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The FSW process and tool parameters play a major role in deciding the joint strength. Joint strength is influenced by grain size and hardness of the weld nugget region. Hence, in this investigation an attempt was made to develop empirical relationships to predict grain size and hardness of weld nugget of friction-stir-welded AA6061 aluminium alloy joints. The empirical relationships are developed by response surface methodology incorporating FSW tool and process parameters. A linear regression relationship was also established between grain size and hardness of the weld nugget of FSW joints.

Developing Empirical Relationships to Predict Grain Size and Hardness of the Weld Nugget of Friction Stir Welded AA7075-T6 Aluminium Alloy Joints

High-strength, precipitation-hardening AA7075-T6 alloy is used extensively in aircraft primary structures. Friction stir welding process is an emerging solid state joining process in which the material that is being welded does not melt and recast. The FSW process and tool parameters play a major role in deciding the joint strength. Joint strength is influenced by the grain size and hardness of the weld nugget region. Hence, in this investigation an attempt has been made to develop empirical relationships to predict the grain size and hardness of the weld nugget of the friction stir welded AA7075-T6 aluminium alloy joints. Six factors, five levels, central composite, rotatable design matrix is used to optimize the experimental conditions. The empirical relationships are developed by response surface methodology incorporating tool and process parameters. A linear regression relationship is also established between grain size and hardness of the weld nugget of friction stir welded joints. The weld nugget grain size is related with hardness of the joint. The developed relationships can be effectively used to predict the weld nugget grain size of the joint non-destructively by measuring the weld nugget hardness.

Microstructural and Mechanical Characterization of Friction Stir Welded- 1050 Aluminium Alloy

Friction stir welding (FSW) is a fairly recent technique that utilizes a non-consumable rotating welding tool to generate frictional heat and plastic deformation at the welding location in the continuously-fed work piece. In the present investigation this welding process is applied to join 1050 cold-rolled aluminium plates. The effects of varying the welding parameters namely welding speed [56, 90 and 140 mm/min] and tool rotational speed [850 and 1070 rpm] on the mechanical and microstructural properties were studied. Vickers micro hardness results across the weldment showed that the weld nugget hardness is dependant upon the welding speed and the tool rotational speed. Increasing the welding speed at 850 rpm reduced the hardness at the weld nugget, whereas, at 1070 rpm the weld nugget hardness merely did not change. However, the hardness achieved at 850 rpm was constantly higher than that achieved with 1070 rpm irrespective to welding speeds. In the same fashion, the yield and ultimate strengths of the joints were influenced by varying the welding parameters. Increasing the welding speed at 850 rpm reduced both strengths whereas; at 1070 rpm they were almost unchanged. Microstructural study showed that the weld region is composed of unaffected base metal and the stir zoned [weld nugget] which is characterised by a fine equiaxed grain structure. Increasing the welding speed at constant tool rotational speed has caused a slight refinement in the weld nugget's grain size, whereas, decreasing the rotational speed has also led to weld nugget grain refinement.

Effect of weld nugget size on overload failure mode of resistance spot welds

In the present paper, effects of welding current, welding time, electrode pressure and holding time on the weld nugget size were studied. A failure mechanism was proposed to describe both interfacial and pullout failure modes. This mechanism was confirmed by SEM investigations. In the light of this mechanism, the effect of welding parameters on static weld strength and failure mode was studied. Then, an analytical model was proposed to predict failure mode and to estimate minimum nugget diameter (critical diameter) to ensure pullout failure mode in shear tensile test. On the contrary to existing industrial standards, in this model, critical nugget diameter is attributed to metallurgical characterisation of material (weld nugget hardness to failure location hardness ratio), in addition to sheet thickness. For a given sheet thickness, decreasing HWN/HFL increases interfacial failure mode tendency. The results of this model were compared with experimental data and also with the literature.