Ultra-high strength 7xxx series aluminum alloys are widely used in aerospace applications due to their exceptional high specific strength. Wire + Arc Additive Manufacturing (WAAM) is a combination of arc and wire feeding additive manufacturing technology including either the gas tungsten arc (GTA) or the gas metal arc (GMA) process. And this technology has been applied in the aerospace manufacturing industry to reduce the time of product development and “buy-to-fly” ratios. However, the existing Al-Zn-Mg-Cu aluminum alloy filler wires are not suitable for WAAM process due to their high susceptibility to hot cracks. In this study, a novel Al-Zn-Mg-Cu-Sc aluminum alloy wire named 7A55-Sc with ultra-high strength and excellent hot-crack resistance has been successfully prepared by optimizing the composition of Al-Zn-Mg-Cu alloying elements and adding appropriate amounts of inoculants Sc and Zr elements during the smelting process. And then, thin-wall components without any hot cracks
This paper compares the microstructure and mechanical evolution in a high-strength quenched and micro-alloyed steel during the austenitising bending process. Simulation results indicated a new finding that the stress neutral layer (SNL) tends to move to the tension zone during straining. The hardness gradient detected from the centre to compression/tension zones was resulted from comprehensive factors: First of all, the location of SNL revealed a prominent impact on strength. Second, the dislocation accumulation would be responsible for the hardness gradient on the surfaces. In addition, the overall strength decrease during straining was mainly ascribed to integrated effects of dynamic recovery (DRV) and dynamic recrystallisation (DRX). Apart from that, overall smaller martensite packet size and coarser prior austenite grains resulted in the increased hardness value at a lower bending degree. Also, the high consistency between experimental and simulation results is instructive for the
In this study, microstructure and mechanical properties of wire arc additively manufactured Ti6Al4V alloy with/without magnetic arc oscillation were investigated by means of optical microscopy (OM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), scanning electron microscopy (SEM), and standard tensile testing. The results show that for Ti6Al4V thin-wall components fabricated in current work, the addition of synchronized magnetic arc oscillation, including both arc oscillation and arc rotation, leads to a refinement of lamellar α width, modification of texture orientation, and then increases in low angle grain boundaries. Meanwhile, the mechanical properties (yield strength and ultimate tensile strength) of the deposition with magnetic arc oscillation are improved. The findings reveal that the arc oscillation routes can be used in wire arc additive manufacturing to create a stirring effect in deposition, which is beneficial to improvement of material properties.
A systematic study was carried out on a novel designed austenitising bending process to explore the effects of quenching temperatures on the evolution of microstructure and mechanical properties of high-strength micro-alloyed steel. Results reveal that the qualified parts could be bent into a satisfactory shape without spring-back and cracks in bending temperatures of 850–1000 °C. The simulation was applied to predict the equivalent stress, stress neutral layer (SNL) and plate thickness. Strength presents a decreasing trend with the increase of bending temperature owing to integrated influences of high-temperature dynamic recovery (DRV) and dynamic recrystallisation (DRX). Beyond that, SNL nearby the geometrical centre line throughout the plate thickness and dislocation pile-ups on the tension/compression zones are responsible for the smaller hardness on middle regions while higher hardness on the surface areas. Through austenite reconstruction, a smaller martensite packet size woul
The austenitising bending process was conducted on a medium-carbon micro-alloyed steel by Gleeble 3500 thermomechanical simulator to comparatively investigate the microstructural and mechanical evolution through thickness of the bent plate. A combination of bainite ferrite, lath martensite and acicular ferrite with a presence of partial dynamic recrystallisation was the main microstructural features. The increased work hardening in the compressive and tension zones after austenitising bending operation can be ascribed to synergistic effects of dislocation pile-up/cells, and finer prior austenite grains. Also, the reliability of this study was verified from the consistency between the results of simulation and experiment, which would provide a valuable reference for the practical manufacturing technology of railway spring clips.