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In this study, a new alloy material Mg-Zn-Zr (ZK60) was designed for the connecting rod. It was found that the blanks sampled along the vertical direction of an extruded bar crack during the roll forging process. The microstructure and precipitates of the extruded bar were observed and analyzed using optical microscope (OM), scanning electron microscope (SEM) and x-ray diffraction (XRD). The result showed that the Zn, Zr, and MnZn2 precipitates were elongated along the extrusion direction. The mechanical anisotropy was investigated by testing the mechanical properties of the specimens sampling from different angles. Hot deformation behavior was further studied using the Gleeble 3500 thermal-mechanical simulator. The tensile and yield strengths were the highest along the extrusion direction, reaching 347 MPa and 301 MPa, respectively. The deformation resistance was also higher in the extrusion direction than that in the vertical direction. Fracture mechanisms of the sample from different directions were discussed. The ZK60 alloy was more susceptible to failure if the deformation direction was parallel to the bands of segregation area and precipitates. [ABSTRACT FROM AUTHOR]

The mechanical strength of commercial Al alloys rarely exceeds 700 MP. Recent studies show that nanotwinned Al alloys and other nanocolumnar metals exhibit superb mechanical behaviors but a discrepancy between tensile and hardness measurements often emerges and their orientation dependent deformation mechanisms remain unclear. Here, we inspect the mechanical response of columnar nanotwinned Al–Fe alloys with emphasis on response of grain boundaries to in-situ tension and compression tests along both in-plane and out-of-plane directions inside a scanning electron microscope. Our studies reveal ultra-high out-of-plane tensile and compressive stress, exceeding 1.8 GPa, and an in-plane tensile and compressive stress of 1.1 and 1.6 GPa, respectively. Post-mortem TEM analyses were performed to elucidate the orientation-dependent plastic anisotropy and tension-compression asymmetry in columnar nanotwinned Al–Fe alloys. This study provides an important forward step towards the understanding of deformation mechanisms in high-strength nanotwinned Al alloys and metals with nanocolumnar or non-equiaxed grains. Image 1 • Comprehensive in-situ micromechanical tensile and compressive techniques are demonstrated. • Mechanical response of columnar nanotwinned Al-Fe alloy to stress parallel and normal to directional boundaries is unveiled. • Strengths from four test modes vary from ~ 1 to 2 GPa, except for an unprecedent out-of-plane tensile strength of ~ 1.8 GPa. • Strength, plastic deformation and deformation/fracture mechanism are anisotropic and loading mode dependent. • Tension-compression asymmetries show apparent orientation dependence. • It reveals that susceptibility of grain boundaries to fracture can be alleviated in metals with non-equiaxed nanograins. [ABSTRACT FROM AUTHOR]