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In this study, the plastic flow and ductile fracture of three 6000-series aluminium alloys commonly used for crash components in the automotive industry are characterised experimentally and the observations are related to microstructural features. The three alloys are used in the cast and homogenised condition after artificial ageing to temper T6 to ensure isotropic behaviour. Tension tests on smooth and notched axisymmetric specimens are carried out to reveal the stress–strain behaviour, ductility and fracture mechanisms of the materials for different stress states. Through the use of optical and scanning electron microscopes, the initial microstructure of the alloys and the fracture surfaces of the tension test specimens are investigated. The work-hardening of the alloys is analysed up to large strains. Whereas the ductility of two of the alloys falls into the trend of previous experimental data on 6000-series aluminium alloys, where the strain to failure decreases linearly with increasing yield stress, the third alloy stands out by combining high strength with high ductility. The excellent properties of the latter alloy are assumed to be due to a favourable size distribution of constituent particles. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is a promising additive manufacturing technique with growing acceptance in aerospace applications. In this work, a new aeronautical material of near-α Ti alloy (TA15) for SLM was firstly investigated and analyzed before and after annealing, mainly including mechanical properties, microstructural evolution. The distinctions between SLMed TA15 and wrought TA15 are also discussed in this study. Firstly, near full density TA15 samples (99.98%) were fabricated by SLM utilizing the optimized processing parameters. Then microstructures and textures are characterized and analyzed by optical microscope, X-ray diffractometer, scanning electron microscope and transmission electron microscope. Furthermore, mechanical properties of TA15 samples are measured via tensile and hardness test, considering the impacts of building direction. The results show that both the as-built and the annealed SLMed samples exhibit significantly weak textures and unconspicuous anisotropy of mechanical properties. It has been identified that αʹ martensite is dominant in the as-built microstructure thus contributing to ~1296 MPa in ultimate strength and ~398 HV in hardness which are 35% and 24% higher than those of wrought material. However, a low plasticity with ~7.6% of elongation at break was observed. After annealing, SLMed samples exhibited excellent comprehensive mechanical properties with 51% improvement at elongation through elimination of residual stress and precipitation of nanometer size β phase in the fine basket-weave structure. [ABSTRACT FROM AUTHOR]

The Mg–1Al– x Y (x = 3, 5, 8) alloys were prepared by melting technology and extruded at 400 °C. Microstructures of the alloys were investigated by X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscope (SEM). Tensile properties of the alloys were measured. The results showed that the as-extruded Mg–1Al– x Y (x = 3, 5, 8) alloys were composed of α-Mg phase and Al 2 Y phase and the microstructures were main dynamic recrystallization. The eutectic Al 2 Y phase was broken down to finer particles and dispersed more uniformly after the extrusion. The extruded alloys have (0002) basal plane texture. The tensile strength, yield strength and elongation of Mg–1Al–8Y alloy were 288 MPa, 174 MPa and 20% at room temperature, respectively. Therefore, the alloys have good mechanical properties and the fracture morphology with ductile features. [ABSTRACT FROM AUTHOR]