The long, straight grain boundary of the high-entropy alloy (HEA) produced via laser melting deposition (LMD) is prone to cracking due to unidirectional scanning (single wall). To enhance the competitive growth of columnar grains and improve the overall performance of the alloy, a vertical cross scanning method was employed to fabricate FeCoCrNi HEA (bulk). The influence of grain orientation on the microstructure and mechanical properties of FeCoCrNi-LMD was systematically investigated. Microhardness tests and tensile tests were conducted to assess the mechanical property differences between the single-wall and bulk samples. This study shows that using a single scanning strategy results in monolayer wall grains sized at 129.40 μm, with a max texture strength of 21.29. Employing orthogonal scanning yields 61.15 μm block-like grains with a max texture strength of 11.12. Dislocation densities are 1.084 × 1012 m−2 and 1.156 × 1012 m−2, with average Schmid factors of 0.471 and 0.416
Porosity defects are the main issues faced by aluminum alloys manufactured by wire-arc directed energy deposition (WA-DED), which seriously affect the mechanical properties of WA-DED aluminum alloys, especially the fatigue properties. Thus far, there is still no effective solution for the elimination of porosity in high-strength WA-DED aluminium alloys. In this study, an innovative hybrid WA-DED + interlayer friction stir processing (FSP) method was applied to successfully fabricate thick-walled Al-Zn-Mg-Cu-Sc-Zr aluminum alloy component with enhanced strength-ductility and fatigue properties by utilizing a custom 7B55-Sc wire. The porosity defects caused by the WA-DED process were significantly reduced in the FSP effective zone, and the original continuous grain boundary eutectic structures were broken up and dispersed along the grain boundaries. The grains were also further refined with an average size of about 1.1 ± 0.2 μm in the stirring zone (SZ) and 1.6 ± 0.3 μm in the overla
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The heat treatment process is a vital step for manufacturing high-speed railway spring fasteners. In this study, orthogonal experiments were carried out to obtain reliable optimised heat treatment parameters through a streamlined number of experiments. Results revealed that a better comprehensive mechanical performance could be obtained under the following combination of heat treatment parameters: quenching temperature of 850 °C, holding time of 35 min, medium of 12% polyalkylene glycol (PAG) aqueous solution, tempering temperature of 460 °C, and holding time of 60 min. As one of the most important testing criteria, fatigue performance would be improved with increasing strength. Additionally, a high ratio of martensite to ferrite is proven to improve the fatigue limit more significantly. After this heat treatment process, the metallographic microstructure and mechanical properties satisfy the technical requirements for the high-speed railway practical operation. These findings provid
In this study, the high strength-ductility properties of wire-arc additive manufactured (WAAM) Al-Mg-Sc aluminum alloy were achieved by friction stir processing post-treatment (FSPPT) and high temperature aging treatment (HTAT). The FSPPT significantly refined the microstructure and eliminated porosity defects, which the average grain size was about 2.4 ± 0.2 μm in stirring zone (SZ). There was no obvious growth in grain size after HTAT and the average grain size was about 2.7 ± 0.4 μm in SZ. Many fine secondary Al3(Sc,Zr) phases were precipitated. Compared to WAAM sample, the average ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of FSPPT + HTAT sample increased by 57.9%, 54.7% and 205.9%, respectively.