A review of various improvement strategies for joint quality of AA 6061-T6 friction stir weldments

Aluminium alloys are one of the choice materials with ever-increasing demands in manufacturing industries. The aluminium alloy 6 xx series such as AA6061-T6, has emerged as one of the promising materials utilized owing to its combination of favourable properties which include high strength to weight ratio, good ductility, excellent corrosion resistance and relatively low cost. These superior properties are responsible for its emergence and usage in the fabrication of aircraft wings and fuselages, yacht/ship construction, automotive rims and wheel spacers. However, joining of AA6061-T6 including the use of friction stir welding (FSW) has serious concerns because the mechanical and tribological properties of the AA6061-T6 welded joints deteriorate significantly compared with the base metal. This phe�nomenon has been attributed to the severe softening encountered at the stir zone (SZ) of the aluminium matrix during FSW. Other inherent challenges of FSW such as weld thinning, kissing bond and keyhole formation also contribute to the reduction in the weld joint quality. The softening phenomenon has been linked to the dissolution of the strengthening pre�cipitates (B00-Mg5Si6) as a result of high heat input during the welding process. Hence, this paper attempts to review the various improvement strategies adopted in the existing studies to improve the quality of AA 6061-T6 welded joint. These include parametric optimization, selection of appropriate tool design, pre and post heat treatments, adoption of different groove/hole designs for particle addition as well as the addition of reinforcement particles to the weld joint. The variants of FSW recently developed will also be considered. The findings from the review will generally be useful for future work on FSW of heat treated aluminium alloys. The evolution of FSW and its associated challenges are briefly discussed while the research areas yet to be harnessed are suggested for future works

Low temperature In–Bi–Zn solder alloy on copper substrate

In this paper, characteristic of In–32.7Bi–0.5Zn lead-free solder system have been studied. DSC shows that, In–32.7Bi–0.5Zn system alloy give low melting temperature at 72.30 °C. Lowest melting temperature ensures that the solder melts, forms a joint with the substrates, and re-solidifies within the shortest possible process time. Further, the wettability between molten solder and copper substrate was measured at different reflow temperature. The contact angle for In–32.7Bi–0.5Zn solder alloys were decreasing 30.76° to 24.5° as the temperature increased from 100 to 140 °C. A significant increment of contact angle for In–32.7Bi–0.5Zn at 140 °C. The result of spreading area is inversed with the contact angle. Energy-dispersive X-ray analysis indicated two layer of intermetallic compound between the solder and the substrate; Cu5Zn8 and Cu11In9 compound

Review of post-processing methods for high-quality wire arc additive manufacturing

The present paper reviews the concept of wire arc additive manufacturing (WAAM), its associated defects, and the existing post-processing methods for product quality enhancement. The application of friction stir processing (a surface modification technique) for enhancing the microstructure and mechanical properties of wire arc additively manufactured parts was considered as a new horizon in this field of research. Finally, the article concludes that the widespread usage of WAAM is still challenged by some obstacles, which may need to be targeted and addressed in unique ways for different materials in order to generate functional systems in a reasonable amount of time. Unifying materials and manufacturing techniques to produce defect-free and structurally robust deposited parts will become increasingly important in the future.<br/

Titanium carbide reinforcement in iron matrix through carbothermal reduction of mechanically milled hematite and anatase

This study investigated the influence of the duration of milling on the formation of TiC-reinforced iron composite through carbothermal reduction of a hematite and anatase mixture. Mixtures of hematite, anatase, and graphite powders were mechanically activated in a planetary ball mill in an argon atmosphere with different milling times (0 to 60 hours). X-ray diffraction showed that with increasing milling time, the crystallite size of the hematite decreased to nanometer range, accompanied by an increment in internal strain. Prolonging the milling process increased dislocation density of the as-milled powder. The as-milled powder was consolidated by cold pressing under 100 MPa and sintered in vacuum at 1373 K (1100 °C). High temperature during sintering resulted in the formation of iron and titanium carbide phases as confirmed by X-ray diffraction, scanning electron microscope, and energy dispersive X-ray analysis. Without mechanically activated milling, the reaction forming TiC did not occur during sintering at 1373 K (1100 °C), indicating a reduction in reaction temperature promoted by mechanical milling. An increase in milling time resulted in an increase in sintered density and hardness due to the fineness of the composite powder, together with complete TiC and iron phase formation