Solidification Of Aluminum Alloys Research Articles

Effect of hollow core on cooling temperature in 3D printing

3D printing is a very promising method for sand mold manufacturing with a shorter design time and simpler manufacturing process compared with conventional technology in the casting industry. The heat preservation and feeding effect of the riser can effectively reduce the occurrence of shrinkage cavity and porosity in the casting. Therefore, the insulation effect of the riser is an important index to evaluate sand mold design. In this study, a hollow sand core was designed and used for casting a cylindrical thin-walled part by the binder jetting 3D printing method. The temperature change curve of the hollow core during the No. 35 steel pouring process and the riser site during the A356 aluminum alloy solidification process in this sand mold was tested to explore the effect of the hollow core on the cooling process. The A356 pouring results showed that the concretion time of the riser with a hollow core was prolonged by over 20%; the cooling rate of casting was accelerated by over 20% by applying this hollow core before sand shakeout. The No. 35 steel pouring facts reflected that the temperature rise rate of the solid core was more visible than that of the hollow core in the early process of casting solidification. The work in this paper indicated that a sand core with a hollow structure could not only accelerate casting cooling but also draw out the concretion duration of the riser to improve its supplying function and can reduce the thermal expansion of the sand core. This study provides a new and effective design idea for 3D printed sand core, which can be used as a reference for the design of 3D sand core molds and the research of casting solidification and cooling.

Grain Refiner Settling and Its Effect on the Melt Quality of Aluminum Casting Alloys.

Grain refiner particles, which are intended to induce the formation of fine equiaxed grain structure during the solidification of aluminum alloys, are prone to settling during the holding of the liquid metal, which phenomenon can affect not only the grain size but the spatial distribution of the double oxide films in the melt. In this study, the settling of Al3Ti inoculant particles, as well as its effects on melt quality and grain refinement, were studied. During the experiments, the Ti-concentration of a liquid Al-Si-Mg-Cu alloy was increased to 0.3 wt.% by the addition of Al-10%Ti master alloy at different melt temperatures. Particle settling and grain size evolution were studied by quantitative metallography, while the interactions of grain refiners and bifilms were investigated by scanning electron microscopy (SEM). The evolution of melt quality was assessed by the computed tomographic (CT) analysis of reduced pressure test (RPT) samples. It was found that effective grain refinement was only realized when the introduced blocky Al3Ti particles were dissolved and re-precipitated in the form of (Al,Si)3Ti at a lower temperature. Without dissolving at higher holding temperatures, Al3Ti particle settling has taken place within 10 min. The settling of (Al,Si)3Ti particles improved melt quality by the aided sedimentation of bifilms in the melt.

Cast and Rapidly Solidified Aluminium Alloy with the Addition of Deep-sea Nodules

Reduced deep-sea nodules were tested as the alloying mixture for cast and rapidly solidified aluminium alloy. No separation of any metal was used in order to save the processing costs of the deep-sea nodules and to obtain “natural” ratios between the alloying elements. The resulting rapidly solidified alloys contained sharp-edged intermetallics, especially Al9Mn3Si phase, which was converted to rounded Al19Mn4 during thermal exposure. The hardness of the ribbons was almost stable during long-term annealing at 300 and 400 °C for 250 h. The alloy can be considered as highly thermally stable.

Predicting Flow Stress Behavior of an AA7075 Alloy Using Machine Learning Methods

The present work focuses on the prediction of the hot deformation behavior of thermo-mechanically processed precipitation hardenable aluminum alloy AA7075. The data considered focus on a novel hot forming process at different tool temperatures ranging from 24∘C to 350∘C to set different cooling rates after solution heat-treatment. Isothermal uniaxial tensile tests in the temperature range of 200∘C to 400∘C and at strain rates ranging from 0.001 s−1 to 0.1 s−1 were carried out on four different material conditions. The present paper mainly focuses on a comparative study of modeling techniques based on Machine Learning (ML) and the Zerilli–Armstrong model (Z–A) as reference. Related work focuses on predicting single data points of the curves that the model was trained on. Due to the way data were split with respect to training and testing data, it is possible to predict entire stress–strain curves. The model allows to decrease the number of required laboratory experiments, eventually saving costs and time in future experiments. While all investigated ML methods showed a higher performance than the Z–A model, the extreme Gradient Boosting model (XGB) showed superior results, i.e., the highest error reduction of 91% with respect to the Mean Squared Error.

Investigation of Cracks on Internal Surfaces of Extruded Cold Worked Thick Walled Pipes of an Age Hardened Al-Alloy

Thick seamless pipes of hardenable aluminum alloys demand close geometrical tolerances as well as high quality surface finish which are met by cold drawing after a series of different thermo-mechanical treatments. To meet the requirements of critical applications the final product undergoes stringent quality inspection procedures. State of the art quality assessment can detect even minor isolated defects. The production facilities develop their quality criteria suitable for specific applications. The present study investigated minute defects on the inside surface of thick seamless pipes, proposed mechanism of their formation and suggested the impact of defects on the end use. The root cause analysis was conducted, and measures were suggested to control the defects. Thick extruded seamless aluminum alloy pipes underwent a series of different thermo mechanical treatments; the final dimensions with required tolerances and the surface finish were achieved by adopting a 2-step cold drawing process. Cold drawing generated residual stresses which resulted in the formation of cracks in the material, preferentially at the defects generated during solidification and/or extrusion processes. The final product underwent stringent quality inspection, and the material was rejected if cracks of size 3 mm or larger were detected. The die scratches or notches generated on the inside surface of the pipes, during extrusion are assumed to grow if subjected to high stresses during subsequent processes, e.g. cold working. Observations at high magnification in SEM helped to determine the morphology of cracks. Radiographic testing did not detect any crack in the bulk material. Particles with faceted features indicated the presence of inclusion. Inclusions were detected in the form of strings along the direction of cold drawing. Energy dispersive spectrometry in SEM was used to determine the composition of inclusion detected in the vicinity of cracks. Almost all the inclusions were rich in silicon, iron, calcium along with carbon; it indicated that the inclusions were trapped particles of fluxes, slag, and brick powder. Particles rich in Ca, Na and/or Cl indicated entrapped flux, Fe and Si were mostly coming from aluminum scrap and refractory powder while presence of carbon indicated entrapped extrusion lubricant. Inclusions rich in a large variety of unwanted elements indicated presence of slag particles. Numerical analysis was conducted to develop a model in FEM in which scratches of different depths were introduced and autofrettage pressure was applied to determine the stresses generated according to the established Von Mises Model; the latter was used to establish the yield criteria. Finite Element Modelling concluded that when cold drawing pressure was applied on a pipe with a single notch of depth 0.3mm or three notches of depth 0.1 or greater at different locations the Von Mises stresses approached the yield strength of the pipe.

Electrochemical corrosion of AA6061-AA7075 double sided FSW joints prepared with and without secondary heating

The present study aims to evaluate corrosion behavior of different zones in the double-sided dissimilar friction stir weld between precipitation hardening aluminum alloys AA6061-T6 and AA7075-T651 of 12.7 mm thickness obtained without and with employing secondary/additional heating. Each specific zone of the welds is tested for corrosion potential, corrosion current and impedance spectroscopy. The stir zone formed is more corrosion resistive than AA7075 but less in comparison to AA6061. The corrosion resistivity of AA7075 dominated region increases significantly on the application of secondary heating. The increase is attributed to the disintegration of large corrosion susceptible precipitates due to intense mixing and stirring facilitated at elevated temperature with the application of additional heating. Although, AA6061 experienced trivial decrease in corrosion resistance as high working temperature resulted in increased grain boundary along with high misorientation angle. The scanning electron microscopic images and elemental line scan at corroded stir zone identified AA7075 as the sacrificed alloy due to galvanic coupling with AA6061 at macroscopic scale and dissolution of Mg/Si at microscopic scale. The regions with higher percentage of high angle grain boundaries observed to undergo faster corrosion rates. The heat produced in second pass left annealing effect on prior welded region wherein lower microhardness is noted. • Corrosion resistance of SZ in AA6061-AA7075 DS-FSW joints is enhanced compared to AA7075 while reduced compared to AA6061. • HAZ and TMAZ on RS (AA7075) showed significantly increased corrosion resistance employing secondary heating. • Breakdown of corrosion sensitive intermetallic helped in increasing corrosion resistance. • Slight drop in corrosion resistance of AA6061 observed after secondary heating as increased fraction of HAGBs promoted IGC.

Microstructure, Tensile, and Fractography Analysis of Al2016 and Al2618 Age Hardened Aluminium Alloys

This experimental project is dealt with two high-strength aluminium alloys, termed Al2016, Al2618. Objective of this research is to contribute to a good clarifi cation on microstructural and tensile properties of distinct grades of Al2016 and Al2618 alloys to be used in the aerospace fi eld as skin materials. These two different grades of twin-rolled aerospace metallic materials were received for investigation after those were subjected to two different conditions of heat treatment processes namely artifi cially aging and overaging. Those four specially processed alloys are specifi ed as Al2016-T6510, Al2016-T7510, Al2618-T6510, and Al2618-T7510 based on the treatment. This article discusses the physical characteristics and tensile behavior of those alloys through the outcome of light microscopy test and tensile tests. Particle size variations and origination of grains play a major role in mechanical behavior. When comparing the various tensile properties of radial longitudinal and transversely oriented specimens of all specifi ed graded alloys possess almost a similar tensile behavior between each grade. Broken specimens of tensile tests were employed for investigating the fractographic conditions through scanning electron microscopy. As result, ductile ruptures were commonly registered in all the grades of materials whereas the evidence for intergranular fracture was found in Al2016-T6; and a transgranular fracture was noti ced in Al2016-T6. Amongst all the grades, a greater number of intergranular compounds were found in the Al2618-T6 alloy. T6 and T7 conditioned alloys of both grades revealed that the denseness of precipitation increases due to overaging, which in turn ends in declination of ductility. In general, other attributes of such T7 conditioned aluminium alloys have contributed well to elevated temperature applications especially, in stress corrosion cracking resistance.

On the elimination of solidification cracks in fusion welding of Al7075 by TiC-nanoparticle enhanced filler metal

Solidification cracks in fusion welding of high strength and precipitation hardened aluminum alloys have been a major challenge for many years. In this research, the weldability of 3-mm thick Al7075 sheets in fusion arc welding was investigated. Welding was conducted with (heterogeneously) and without (autogenously) TiC-nanoparticle enhanced Al7075 filler metal. Results show that the nanoparticles were effective in eliminating welding solidification cracks completely. Two mechanisms are proposed: (1) TiC nanoparticles act as nucleants in the early stage of solidification to alter the microstructure from dendritic to equiaxed and to refine the grains; (2) TiC-nanoparticles act as nucleants in the late stage of solidification to change the shape of eutectic precipitates from continuous to discontinuous and to promote the formation of the Al-Cu-Mg phase at the expense of the deleterious Mg(Cu,Zn)2 (η) phase. Tensile mechanical properties of autogenous weld could not be obtained due to large solidification cracks. In contrast, the heterogenous joint showed relatively good tensile strength and ductility that, however, were slightly lower compared to unwelded Al7075. This was directly linked to the high amount of porosity in the fusion zone due to the use of non-optimal welding parameters adopted in this study to promote solidification cracking for better comparative study and investigation of effects of nanoparticles.

Statistical Assessment of Low-Cycle Fatigue Durability

This article presents an experimental–analytical statistical study of low-cycle fatigue to crack initiation and complete failure. The application of statistical and probability methods provides for the possibility of improving the characteristics related to the structural life and the justification for the respective values of cyclic loads in the design stage. Most studies investigating statistical descriptions of crack initiation or complete failure do not analyse the distribution of the characteristics, correlation relationships, and statistical parameters of low-cycle fatigue. Low-cycle failure may be quasistatic or (due to the fatigue) transient. Materials with contrasting cyclic properties were selected for the investigation: cyclically softening alloyed steel 15Cr2MoVA; cyclically stable structural steel C45; cyclically hardening aluminium alloy D16T1. All samples were produced in a single batch of each respective material to reduce the distribution of data. The lowest values of the variation coefficient of one of the key statistical indicators were obtained using the log-normal distribution, which is superior to the normal or Weibull distribution. Statistical analysis of the durability parameters showed that the distribution was smaller than the parameters of the distribution of the deformation diagram. The results obtained in the study enable the verification of durability and life of the structural elements of in-service facilities subjected to elastoplastic loading by assessing the distribution of characteristics of crack initiation and failure and low-cycle strain parameters as well as the permissible distribution limits.

Effect of Tool Geometry and Turning Parameters on Cutting Force during Ultra-Precision Diamond Machining of Rapidly Solidified Aluminum (RSA) Alloy 6061

The most important goal of advanced diamond machining is to improve precision and product integrity. Cutting force could have a strong effect on diamond machining performance and hence, it can be used as an indicator for monitoring tool condition for achieving successful machining. Moreover, diamond machining process parameters such as cutting speed, depth of cut and feed rate may strongly influence the process outcomes in terms of surface roughness and tool failure. Diamond machining parameters have a significant role on the cutting force values, and machine-tool stability during ultra-high precision machining that makes use of a natural diamond cutting tool. The main objective of this research work is to investigate the effect of cutting speed, feed rate, depth of cut and nose radius on the cutting force generated during diamond turning of a rapidly solidified aluminum alloy grade called RSA 6061. The effect of nose radius and cutting parameters on cutting force during the ultra-high precision diamond turning process was monitored. The study shows that low speed, low depth of cut and an increase in feed rate at large nose radius consequently results in increase in the cutting force.

PENGARUH TEMPERATUR TUANG TERHADAP POROSITAS, STUKTUR MIKRO DAN KEKERASAN DARI ALUMUNIUM RONGSOK BALING-BALING KAPAL MENGGUNAKAN PENGECORAN EVAPORATIF

Aluminum and its alloys are the second largest metal material used after steel. Aluminum applications and alloys are very diverse, ranging from buildings, vehicle bodies, engine components, components to ships, to applications on aircraft. The strength and hardness of aluminum alloys are high, one application of aluminum as a component on a ship is as a material for making propellers on traditional fishing boats, more specifically aluminum alloy. Used aluminum can be obtained from the remnants of the industry making aluminum doors, windows and frames, making aluminum racks and storefronts, and other products with aluminum profile as the main material. many of them use aluminum alloy scrap as their main casting material to reduce their production costs. Evaporative or casting casting using Styrofoam or lost foam casting patterns is casting using a pattern of materials that can evaporate when exposed to molten metal heat. Casting uses a temperature of 650°C, 700°C, 750°C, 800°C. The results of casting temperature can affect porosity, microstructure, and hardness.

Influence of solidification rates and heat treatment on the mechanical performance and joinability of the cast aluminium alloy AlSi10Mg

In modern vehicle chassis, multi-material design is implemented to apply the appropriate material for each functionality. In spaceframe technology, both sheet metal and continuous cast are joined to castings at the nodal points of the chassis. Since resistance spot welding is not an option when different materials are joined, research is focusing on mechanical joining methods for multi-material designs. To reduce weight and achieve the required strength, hardenable cast aluminium alloys of the AlSi-system are widely used. Thus, 85–90% of aluminium castings in the automotive industry are comprised of the AlSi-system. Due to the limited weldability, mechanical joining is a suitable process. For this application, various optimisation strategies are required to produce a crack-free joint, as the brittle character of the AlSi alloy poses a challenge. Thus, adapted castings with appropriate ductility are needed. Hence, in this study, the age-hardenable cast aluminium alloy AlSi10Mg is investigated regarding the correlation of the different thicknesses, the microstructural characteristics as well as the resulting mechanical properties. A variation of the thicknesses leads to different solidification rates, which in turn affect the microstructure formation and are decisive for the mechanical properties of the casting as well as the joinability. For the investigation, plates with thicknesses from 2.0 to 4.0 mm, each differing by 0.5 mm, are produced via sand casting. Hence, the overall aim is to evaluate the joinability of AlSi10Mg and derive conclusions concerning the microstructure and mechanical properties.

Evaluation on hardness and percentage of elongation discrepancy by Zinc oxide nanoparticles on AA6070 alloy composites

The nano particles are the most important materials to develop the mechanical properties of the materials due to its grin structure and size. In this investigation deals with the (20–30 nm) Zinc oxide (ZnO) nanoparticles volume participation effect on the AA6070 aluminium alloy composite based on the major mechanical properties like hardness and percentage of elongation. The hardened aluminium alloy is used here due to the better results. The composites were prepared by the stir casting method. The ZnO nanoparticle is increased from zero to 12.5% of volume with 2.5% incremental in each specimen and remaining volume percentage is occupied by hardened AA6070 Aluminium alloy. Among all the specimens 7.5% of ZnO nanoparticle mixed composite have maximum hardness and less percentage of elongation.

COMBINED TECHNOLOGY FOR RESTORATION AND HARDENING OF BUSHINGS OF GEAR HYDRO MOTORS USING GAS-DYNAMIC SPRAYING

Over the past 10-15 years, the use of aluminum alloy parts in the structures of hydraulic systems of agricultural machinery has increased significantly. A large proportion of such parts account for sliding bearings (bushings), the working surfaces of which are subjected to significant wear during operation. Micro-arc oxidation is a modern method of hardening aluminum alloy parts, but it does not allow to restore parts with wear greater than 0.15 millimeters. For the restoration of parts made of aluminum alloys with significant wear, the method of supersonic gas dynamic spraying is promising. (Research purpose) The research purpose is analyzing the technical condition of worn bushings REXROTH of gear hydraulic motors and develop a combined technology for restoring their working surfaces by gas-dynamic spraying with subsequent hardening by micro-arc oxidation. (Materials and methods) Sixty bushings were chosen for the study. A digital micrometer MCC-25-0.001 GOST 6507 was used to measure wear. Powders A-80-13 and A-20-11 by Obninsk Powder Spraying Center were used. A silicate-alkaline electrolyte KOH-Na2SiO3 was used for microarc oxidation. (Results and discussion) Based on the information on wear, authors have developed a combined recovery technology with hardening of the end surfaces of gear motor bushings, which includes: cleaning of bushings; fault detection; pre-machining; supersonic gas dynamic spraying of worn surfaces; hardening by micro-arc oxidation; finishing mechanical treatment of the coating and final control. (Conclusions) The developed combined technology of bushings will allow to increase their wear resistance up to 2.2-2.3 times and significantly increase the service life of hydraulic motors. The technology is universal, and the possibility of restoring the bushings of foreign hydraulic motors using the proposed technology is especially relevant due to the need for large-scale import substitution.

Hybrid Heat Treatment for Conventionally Treatable Steel Powder Reinforced Age Hardenable Aluminium Alloy Matrix Composites and Mechanical Property Evaluation

The present work is associated with research concentrating on the innovation and use of hybrid heat treatment for eutectoid steel powder (0.8 wt%) reinforced Al-Zn-Mg (Al 7075) alloy composites. Due to high hardness, wear resistance, tensile strength and flexibility modifying heat treatment, heat treatable aluminium metal matrix composites reinforced with heat treatable hard steel particles may be the choice to explore. In this work, an attempt is made to increase hardness and tensile properties to higher levels through hybrid heat treatment, comprising simultaneous treatment to matrix and reinforcement in 3 different routes (Pearlite, Bainite and Martensite) compared to conventional age hardening treatment. SEM images and microhardness distribution witnessed the phase transformation in both matrix and reinforcement. Aging kinetics in conventional age hardening and hybrid treatments is accelerated by the increase in the quantity of reinforcement and increase in aging temperature. The improvement in hardness and tensile strength obtained by conventional age hardening path is further improved by the hybridisation path. Hybridisation route with martensite reinforcement phase shows excellent result in hardness, strength followed by bainite and pearlite path respectively in the decreasing order. In all heat treatment cycles, lower aging temperature marks greater property enhancement compared to higher temperature. Al 7075 with 6 wt% steel powder reinforced (martensite form) composite showed excellent peak age hardness, tensile strength compared to lesser quantity reinforced composites.

Microstructural and Process Parameters of aluminium alloys Using FSW

Friction stir welding (FSW) has become a popular method for connecting low weight metals. Material joining occurs in the solid state in FSW. Inserting a rotating tool travelling over the faying surfaces of the material to be bonded is used to complete the procedure. It produces practically defect-free welds with little distortion and a fine grain structure. However, the welding mechanism and process parametric combination for welds with consistent and dependable outcomes are not well understood. The thesis details the experimental efforts made to suggest an optimal combination of parameters with simple tool geometry for FSW at greater linear speeds. The materials for research were two precipitation hardenable aluminium alloys: 6mm thick 2219-T87 and 5083H321. The influence of process parameters on weld microstructural changes and defect development was also examined. The optimal combination of process parameters for the FSW of aluminium alloys was proposed, and the most relevant parameter for weld strength and quality was discovered.

Corrosion behavior of age hardening aluminum alloys produced by high-energy ball milling

The influence of high energy-ball milling (HEBM) on corrosion and hardness of age hardening aluminum alloys was investigated. Nanocrystalline age hardening (AA2024, AA6061 and AA7075) alloys were produced by HEBM of pre-alloyed powder and subsequent cold compaction under uniaxial pressure of 3 GPa. Cyclic potentiodynamic polarization and immersion tests were conducted in 0.6 M NaCl solution which revealed significantly increased pitting and protection potentials in the HEBM alloys compared to wrought alloys of same composition. X-ray diffraction analysis and transmission electron microscopy indicated grain refinement below 100 nm in the ball milled alloys which was the major strengthening mechanism in the age hardening HEBM alloys. The superior corrosion resistance and hardness of the age hardening ball milled alloys were attributed to nanocrystalline structure, extended solid solubility and homogenous microstructure- free from coarse intermetallic phases.

Modeling of microstructure formation with gas porosity growth during columnar dendritic solidification of aluminum alloys

In this paper, microstructure formation with gas bubble growth during columnar dendritic solidification has been numerically investigated by using the coupled lattice Boltzmann-cellular automaton-finite difference (LB-CA-FD) model, which combines the physical mechanisms of the redistribution of hydrogen components at the solid–liquid interface and the transportation of hydrogen atoms in liquid. Hydrogen transportation, bubble nucleation and growth are computed by the LB method while the growth of columnar dendrite and the transport of solutes are described by the CA-FD model. Predicted results show that the bubbles begin to nucleate at the roots of primary dendritic trunk and secondary arms, and elongated irregular bubbles are sandwiched between neighboring dendrites after merging and moving during the growth stage. Columnar dendritic change from coarse and ordered to fine and disordered as the cooling rate is increased. Meanwhile, the cooling rate has a significant effect on the incubation time for gas bubbles and the maximum growth rate of porosity. It was found that the misorientation angle has limited effects on the solid fraction and porosity percentage but strongly influences on the morphologies of the columnar dendritic arrays, resulting in the different distributions of bubbles.

Defect formation, microstructure evolution, and mechanical properties of bobbin tool friction–stir welded 2219-T8 alloy

Bobbin tool friction stir welding (BT–FSW) is a novel and effective welding method for aluminum alloys, but microvoid defects are usually formed in the nugget zones (NZ). Therefore, it is important to understand the formation mechanism of microvoid defects and their effect on the fracture behavior of joints. In the present study, 6 mm thick 2219–T8 aluminum alloy plates were subjected to BT–FSW under a constant rotation rate of 300 rpm and welding speeds of 150–500 mm min–1 with the objective of analyzing the evolution of microvoid defects and their effect. The results showed that, lower welding speeds resulted in microvoid defects in the band pattern structure on the retreating side (RS) of the NZ, and the size of the defects decreased with increasing the welding speed, while sound joints were obtained under higher welding speeds. In contrast to conventional FSW precipitation–hardened aluminum alloys with the lowest hardness zone (LHZ) at the heat affected zone (HAZ), the LHZs of the BT–FSW 2219–T8 joints were located at the thermal–mechanically affected zone (TMAZ). Digital image correlation (DIC) of large tensile samples showed that the microvoid defects exhibited an obvious effect on the tensile deformation and fracture behavior of the joints due to the decrease in the maximum strain and lack of necking. Mini-samples in different layers further confirmed that cracks initiated from the microvoid defects in the NZ. However, the sound BT–FSW 2219–T8 joints fractured along the LHZs on the RS, with a maximum joint strength coefficient of 78.1% being achieved.

Tensile Behaviour of Friction Stir Welded Joints of Different Aluminium Alloys

This paper investigates the outcome of base metals and their temper condition on tensile and fracture behavior of friction stir welds of various work and precipitation hardening aluminium alloys in different tempers (AA1100-O, 5052-H, AA5086-O & H25, AA2024-O & T6, and AA6061-T651). The type and temper of aluminium alloys affected the tensile, and fracture behavior of weld joints. The extent of improvement in tensile properties of welded joints increased with a decrease in hardness (i.e., from T6 or H to O) of base metals. Softening was not observed for welded joints when base metal was in an annealed temper and an opposite trend was observed for hardened tempers ‘H’ and ‘T6’. Fracture location moved towards the weld centre with the change in temper from ‘O’ to ‘H’ and ‘T6’, hardness minima were closer to base metal hardness in the first case than later. The mode of fracture was ductile for all the weld joints except AA2024-T6 and AA 6061-T651. Except for AA2024-T6 and AA 6061-T651, all weld joints had ductile fracture mode.