Esther T. Akinlabi

Characterizing the Effect of Laser Power Density on Microstructure, Microhardness, and Surface Finish of Laser Deposited Titanium Alloy

This paper reports the effect of laser power density on the evolving properties of laser metal deposited titanium alloy. A total of sixteen experiments were performed, and the microstructure, microhardness and surface roughness of the samples were studied using the optical microscope (OP), microhardness indenter and stylus surface analyzer, respectively. The microstructure changed from finer martensitic alpha grain to coarser Widmastatten alpha grain structure as the laser power density was increased. The results show that the higher the laser power density employed, the smoother the obtained surface. The microhardness initially increased as the laser power density was increased and then decreased as the power density was further increased. The result obtained in this study is important for the selection of proper laser power density for the desired microstructure, microhardness and surface finish of part made from Ti6Al4V.

Effects of processing parameters on corrosion properties of dissimilar friction stir welds of aluminium and copper

The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy (AA5754) and commercially pure copper (C11000) was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.

Effect of heat input on the electrical resistivity of dissimilar friction stir welded joints of aluminium and copper

This paper reports the effect of heat input on the resulting electrical resistivities of joints between aluminium and copper produced with the friction stir welding process. Welds were produced using three different shoulder diameter tools, viz: 15, 18 and 25 mm by varying the rotational speed between 600 and 1200 rpm and the traverse speed between 50 and 300 mm/min in order to vary the heat input to the welds. The microstructures of the joint interfaces were characterized, and the electrical resistivities measured. The resulting microstructural characterization revealed that metallurgical bonding was achieved at the joint interfaces of the welds produced. It was also observed that the electrical resistivity of the joint increased as the heat input to the welds increases.

Evolving properties of friction stir spot welds between AA1060 and commercially pure copper C11000

Abstract Friction stir spot welding technique was employed to join pure copper (C11000) and pure aluminium (AA1060) sheets. The evolving properties of the welds produced were characterized. The spot welds were produced by varying the rotational speed, shoulder plunge depth using different tool geometries. The presence of a copper ring of different lengths was observed on both sides of the welds indicating that Cu extruded upward into the Al sheet which contributed to obtaining strong welds. The microstructure showed the presence of copper particles in the aluminium matrix which led to the presence of various intermetallics observed by the energy dispersive spectroscopy and X-ray diffraction. The maximum tensile failure load increases with an increase in the shoulder plunge depth, except for the weld produced at 800 r/min using a conical pin and a concave shoulder. A nugget pull-out failure mode occurred in all the friction stir spot welds under the lap-shear loading conditions. High peaks of Vickers microhardness values were obtained in the vicinity of the keyhole of most of the samples which correlated to the presence of intermetallics in the stir zone of the welds.

Types of Functionally Graded Materials and Their Areas of Application

Functionally graded materials (FGMs) are advanced composite materials that are used to solve a number of engineering problems, as well as in the biomedical implant applications for the replacement of human tissues. These materials are used to eliminate the stress singularities that occur, as a result of the property mismatch in the constituent materials in a composite. There are different types of FGMs that are used today, depending on the type of application, for which the material is intended. In this chapter, the different types of FGMs are presented. The areas of application of this novel material are also explained.

Finite Element Modelling of Electrokinetic Deposition of Zinc on Mild Steel with ZnO-Citrus sinensis as Nano-Additive

The electrokinetic deposition of zinc on mild steel substrate under the influence of ZnO-Citrus sinensis nano-additive was investigated numerically using a Finite Element (FE) solver. The conductivity of the Acid chloride plus ZnO-Citrus sinensis nano-additive electrolyte and the properties of Zinc and mild steel electrodes were used as the input codes for the model. The model was designed on a 3-dimensional scale. The boundary conditions were set and the model was meshed using the finer mesh capability in the FE solver. The model was processed and readings of the modelled zinc deposited mild steel were taken, validated and analysed so as to get the optimum parameters from the deposition process. Based on the results, the deposition mass and thickness increased with deposition time with ZnO-Citrus sinensis nano-additive, it is thus recommended that relatively high deposition time should be used in order to achieve optimum deposition.

Influence of processing parameters on laser metal deposited copper and titanium alloy composites

Abstract The laser metal deposition (LMD) was conducted on copper by varying the processing parameters in order to achieve the best possible settings. Two sets of experiments were conducted. The deposited composites were characterized through the evolving microstructure, microhardness profiling and mechanical properties. It was found that the evolving microstructures of the deposited composites were characterized with primary, secondary and tertiary arms dendrites, acicular microstructure as well as the alpha and beta eutectic structures. From the two sets of experiments performed, it was found that Sample E produced at a laser power of 1200 W and a scanning speed of 1.2 m/min has the highest hardness of HV (190±42) but exhibits some lateral cracks due to its brittle nature, while Sample B produced at laser power of 1200 W and a scanning speed of 0.3 m/min shows no crack and a good microstructure with an increase in dendrites. The strain hardening coefficient of the deposited copper composite obtained in this experiment is 3.35.

An Overview on Friction Stir Spot Welding of Dissimilar Materials

Understanding the fundamental process mechanisms of any manufacturing process is vital for its long-term development. Friction Stir Welding (FSW) process was invented and experimentally proven by The Welding Institute (TWI) in 1991 for joining Aluminium alloys. Friction Stir Spot Welding (FSSW) is a variant of the FSW which is found to be environmental friendly and an efficient process. FSSW technique has been gaining ground when compared to resistance spot welding (RSW) and could be used in various industries including, automobiles, ship building, aerospace, electrical and construction. FSSW has been successfully used to join several materials used in the above mentioned industries. In this review, FSSW studies are briefly summarised in terms of the evolving microstructure and mechanical properties between aluminium alloys and other materials such as copper, steel and magnesium.

Modelling of Process Parameters Influence on Degree of Porosity in Laser Metal Deposition Process

Additive manufacturing process is an advanced manufacturing process that fabricates component directly from the three dimensional (3D) image of the part being produced by adding materials layer by layer until the part is completed. Laser Metal Deposition (LMD) process is an important additive manufacturing technique that is capable of producing complex parts in a single manufacturing run. A difficult to manufacture material such as Titanium and its alloys can readily be manufactured using the LMD process. Titanium and its alloys possess excellent corrosion properties that made them to find applications in many industries including biomedical. The biocompatibility of Ti6Al4V made then to be used as implants. Porous implants are desirable in some applications so as to reduce the weight as well as to aid the healing and proper integration of the implant with the body tissue. In this chapter, the effect of laser power and scanning speed on the degree of porosity was investigated and empirically modelled in laser metal deposition of Ti6Al4V. The model was developed using full factorial design of experiment and the results were analyzed using Design Expert software. The model was validated and was found to be in good agreement with the experimental data.

Effect of Scan Velocity on Resulting Curvatures during Laser Beam Bending of AISI 1008 Steel Plates

Forming is a flexible process, by which a variety of different shapes can be produced through mechanical, thermo-mechanical, or thermal [Laser Beam Forming] process. Laser beam forming [LBF] process has been successfully applied to a variety of sheet metal components thereby plastically deforming it. This paper investigates the producing effect of scan velocity on the resulting curvatures and resulting properties of the bent components. The results show that three different curvatures (120, 180 and 240 mm) of 4 mm AISI 1008 low carbon steel plate was successfully produced under an optimized set of process parameters and a direct relationship was observed between the scan velocity and the resulting curvatures. Furthermore, microstructural characterization revealed that the grain structures of the irradiated surfaces are refined with cooling than the bottom due to the nucleation rate of new grains formed at the irradiated surface.