This research work aims at finding the optimum process parameters for the laser welding of AA7020 aluminium alloys. The use of 7xxx series alloys is limited because of weldability problems, such as hot cracking, porosity, and softening of the fusion zone despite its higher specific strength-to-weight ratio. AA7020 aluminium alloy was welded while varying the process parameters so as to obtain optimal welding efficiency. The welded samples were analysed to reveal the microstructure, defects, and mechanical properties of the welded zone. The samples were prepared from a plate of AA7020, which was hot rolled at a temperature of 470 °С to a thickness of 1 mm. The welding was carried out at an overlap of 0.25 mm, duration of 14 ms and argon shield gas flow rate of 15 L/min. Process parameters, such as peak power, welding speed, and pulse shaping, were varied. The samples were welded with Al-5Ti-B and Al-5Mg as filler metals. The welding speed, peak power, and pulse shaping have a great influence on the weldability and hot cracking susceptibility of the aluminium alloy. Al-5Ti-B improves the microstructure and ultimate tensile strength of AA7020 aluminium alloy.

This paper presents the outcome of the production of austempered gray iron (AGI) using forced air cooling as the quenching medium. Samples from Class 20 gray cast iron were prepared for micrographic analysis, x-ray diffraction (XRD) analysis, and mechanical testing. The prepared samples were austenitized at 920°C, soaked for 1 h, force air-cooled to the austempering temperature range of 250°C to 400°C (at 25°C intervals), held for another hour at the austempered temperature to allow for complete phase transformation, and then air-cooled to room temperature. The optical micrograph revealed a unique microstructure consisting of ferrite (α) and high carbon austenite (γHC) called ausferrite, the coarseness of which increases as the austempering temperatures increases. XRD analysis revealed only the peak of the α phase. The estimated effective particle size dα of this phase increases with an increase in austempering temperature. The results of mechanical tests showed significant increases in the tensile strength, hardness, toughness, and ductility of austempered samples of Class-20 grade gray cast iron. Conclusively, AGI has a unique combination of high strength and ductility that makes it suitable for the manufacture of parts in which high strength, high wear resistance, and high ductility are required.

In this work the morphology, the size and the chemical composition of the powders of steel 316L received by the two methods was studied: fusion dispersion by a gas stream and reduction of metal chlorides with the subsequent plasma atomization of the received powder particles. The powder particles received by the first method have a spherical shape (aspect ratio 1,0–1,2) with an average size of 77 μm and are characterized by the absence of internal porosity. Particles of the powder received by the second method also have a spherical shape and faultless structure, however, their chemical composition may vary in different particles. The average size of particles is 32 μm. Though the obtained powders had different properties, the experimental samples received by DLD technology demonstrated by equally high durability (Ultimate strength is 623±5 and of 623±18 MPa respectively) and plasticity (38 and 41% respectively). It is established that mechanical properties of DLD samples increase for 7-10% after treatment of the surface.