Key Engineering Materials Vol. 918

Abstract: Al-Mg alloys with 3, 4.7, 6, 8, and 10%Mg were fabricated using gravity casting with a copper mold at a cooling rate of 30.6 °C/s. Hot forging was conducted at 500 °C with 50% reduction. An increase in Mg content increased the tensile stress but decreased the elongation in the as-cast ingot. The tensile stress and especially the elongation were increased by hot forging. The tensile stress, 0.2% proof stress, and elongation for hot-forged Al-8%Mg were 337 MPa, 154 MPa, and 24%, respectively. These mechanical properties were obtained without heat treatment. The results show that Al-Mg is suitable for cast forging in terms of mechanical properties and energy consumption.

Abstract: Structure and mechanical properties of pure titanium by combined processing of boriding and nitriding with different processing temperatures in the heating furnace have been investigated. The effect of combined processing temperature for 2 h on the structure and mechanical properties of the treated specimens. As a result of the examination, combined processing at all designed temperatures resulted in the formation of titanium nitride, where the content of the nitride depended greatly on the processing temperature. When the processing temperature is 1300°C, the cross-sectional hardness of the hardened layer reaches the maximum. At the same temperature, the bonding strength also reaches the maximum, which is related to the performance of the hardened layer. Based on these results, when the processing temperature is 1300°C, the combined processing of pure titanium can improve the overall performance.

Abstract: Effect of casting conditions on ripple mark and surface crack of as-cast Al-4.7%Mg strip was investigated. A vertical type high speed twin roll caster was used. A casting speed was 30 m/min. Casting conditions were tip-shape of a back-dam plate, gap between a roll and the back dam plate and texture on the roll-surface. The texture on the roll-surface was useful to reduce the ripple mark. In bending test conducted to investigate surface crack of as-cast strip, the texture on the roll surface was effective to the reduce the crack. The position of the crack was not coin side with the position of the ripple mark. This result shows that there is no correlation between the ripple mark and the ductility or the strength of as-cast strip. Small roll load was effective to reduce the crack and degree of the ripple mark. Effect of the roll load on the ripple mark was discussed including solidification delay and seepage of Magnesium.

Abstract: This work investigated the surface tension and kinematic viscosity of the multicomponent Fe_73.5Cu₁Nb₃Si_13.5B₉ melt. A relationship was found between surface tension and kinematic viscosity, which manifests itself in a synchronous change in these quantities at temperatures of 1600 and 1780 K. In the temperature range 1600–1780 K, there is a sharp increase in surface tension upon heating and the same decrease upon cooling. The increase in surface tension during heating was explained by the appearance of a large number of free Nb atoms as a result of the dissolution of the residual crystalline phase in the mushy zone, and their diffusion to the melt surface. The drop in the surface tension on cooling below 1780 K is associated with the liquid–liquid structure transition (LLST), which stimulates the outflow of Nb atoms from the surface in order to form new stable clusters. The LLST manifests itself in a change in the activation energy of a viscous flow, which is higher in the high-temperature region and corresponds to the motion of larger clusters with a length scale of about 1 nm.

Abstract: Fe (0.2, 0.4, 0.6, and 0.8 %) was added to roll-cast Al-4.8%Mg alloy to create a model of recycled Al-4.8%Mg and its effect was investigated. An unequal-diameter twin-roll caster was used. The roll speed was 20 m/min. An as-cast strip was cold-rolled down to 1 mm and annealed. Its mechanical properties were then evaluated. The surface condition of the as-cast strip was not influenced by the Fe content. The thickness of the as-cast strip decreased with increasing Fe content. The tensile strength and 0.2% proof stress increased with Fe content up to 0.4%Fe and then decreased. When 0.8% Fe was added to Al-4.8%Mg, the tensile strength and 0.2% proof stress became higher than those for Al-Mg. Elongation and the limiting drawing ratio gradually decreased with increasing Fe content. When 0.8% Fe was added, elongation in the lateral direction was 19.6% and the limiting drawing ratio was 1.7.

Abstract: The influence of different nitriding temperatures was investigated on the structures and mechanical properties of the treated specimens. Based on the research of nitriding temperature on the properties of pure titanium, the cause of the rresults can be discussed in this research. When the nitriding temperature is 1050°C, the cross-sectional hardness of the hardened layer reaches the maximum. At the same nitriding temperature, the bonding strength also reaches the maximum, which is related to the performance of the hardened layer. In summary, when the nitriding temperature is 1050°C, the nitriding of pure titanium can improve the overall performance.

Abstract: In this study, the effect of die edge radius on crack initiation was discussed in finish blanking. Experiments were carried out using die with rounded cutting edge. As a result, it was confirmed that crack initiation near the punch edge occurred earlier than that near the die edge. It was also confirmed that the burnished surface increased with an increase in the die edge radius. Finite element method was carried out from the initial stage of shearing and until the punch penetration depth was achieved just before the occurrence of the cracks to investigate the distribution of the mean stress. As a result, it was confirmed that the punch stroke, where the mean stress began to increase rapidly to a positive value, increased with an increase in the die edge radius, and the punch stroke at which the mean stress increased rapidly also increased.

Abstract: Forming Fiber Metal Laminates (FMLs) is still challenging. There are some inherent limitations to forming smaller and complex-shaped FML parts. In particular, the process parameters have a major impact on the final FMLs part. In this paper, several investigations were conducted to optimize these process variables. In the investigations, different Blank Holder Gap (BHG) thicknesses were used to predict the optimal range; variable Blank Holder Force (BHF) and Cavity Pressure (CP) were chosen to make the results more convincing. Based on the numerical analysis, it is found that the optimum BHF should be between 10 to 15 KN; CP has a range from 8 to 10 MPa; optimum BHG should be 1.0 mm. And through using these predicted process parameters, a successful Glare cup has been formed. Furthermore, the forming performance of the Glare material is improved and the laminate has shown better formability. Finally, optimized process variables can be used for mass production of FMLs parts.

Abstract: Fibre-reinforced materials have garnered attention due to their significant properties such as abrasion and heat resistance, as well as specific strength, which can result in environmental conservation and improved mechanical properties that can solve the limitation of developing light-weight constructions. A new method of joining stainless steel strands with an aluminium alloy using friction stir forming has recently been developed in our laboratory. In present study, the influence of the process parameters on the mechanical properties of a fibre-reinforced aluminium alloy using friction stir forming was investigated. In particular, the effect of process parameters on microstructure, hardness, and tensile properties of A5083 and A6061 alloys was evaluated. The highest tensile strength was observed at 880 and 1,240 rpm, whereas for lower rotation speeds (440 and 620 rpm), the strength decreased due to low temperatures and lower heat input. Heat treatments were applied to improve the mechanical properties of the developed A6061 fibre-reinforced composite. The effects of process parameters and heat treatment conditions on mechanical properties were experimentally investigated, and it revealed improved mechanical properties after applying T6 and age hardening treatments. It was confirmed that the strength after the heat treatment of A6061 was higher than that of the base material (310 MPa), and a high strength of 345 MPa was obtained at a rotation speed of 1240 rpm. It was concluded that rotational speed and heat treatment conditions significantly affect the metal microstructure and mechanical properties of the joint.