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In order to obtain high-performance aluminum alloy parts fabricated by selective laser melting, this paper investigates the relationship between the process parameters and microstructure properties of AlSi10Mg. The appropriate process parameters are obtained: the layer thickness is 0.03 mm, the laser power is 370 W, the scanning speed is 1454 mm/s, and the hatch spacing is 0.16 mm. With these process parameters, the ultimate tensile strength of the as-printed status is 500.7 ± 0.8 MPa, the yield strength is 311.5 ± 5.9 MPa, the elongation is 7.7 ± 0.5%, and the relative density is 99.94%. After annealing treatment at 275 °C for 2 h, the ultimate tensile strength is 310.8 ± 1.3 MPa, the yield strength is 198.0 ± 2.0 MPa, and the elongation is 13.7 ± 0.6%. The mechanical properties are mainly due to the high relative density, supersaturate solid solution, and fine dispersed Si. The supersaturate solid solution and nano-sized Si formed by the high cooling rate of SLM. After annealing treatment, the Si have been granulated and grown significantly. The ultimate tensile strength and yield strength are reduced, and the elongation is significantly improved. [ABSTRACT FROM AUTHOR]

This paper deals with various selective laser melting (SLM) processing strategies for aluminum 2618 powder in order to get material densities and properties close to conventionally-produced, high-strength 2618 alloy. To evaluate the influence of laser scanning strategies on the resulting porosity and mechanical properties a row of experiments was done. Three types of samples were used: single-track welds, bulk samples and samples for tensile testing. Single-track welds were used to find the appropriate processing parameters for achieving continuous and well-shaped welds. The bulk samples were built with different scanning strategies with the aim of reaching a low relative porosity of the material. The combination of the chessboard strategy with a 2 x 2 mm field size fabricated with an out-in spiral order was found to eliminate a major lack of fusion defects. However, small cracks in the material structure were found over the complete range of tested parameters. The decisive criteria was the elimination of small cracks that drastically reduced mechanical properties. Reduction of the thermal gradient using support structures or fabrication under elevated temperatures shows a promising approach to eliminating the cracks. Mechanical properties of samples produced by SLM were compared with the properties of extruded material. The results showed that the SLM-processed 2618 alloy could only reach one half of the yield strength and tensile strength of extruded material. This is mainly due to the occurrence of small cracks in the structure of the built material. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties of 36 aluminum alloy specimens subjected to repeated tensile loading were tested. The failure characteristics, stress-strain hysteresis curves and its corresponding skeleton curves, stress cycle characteristics, and hysteretic energy of specimens were analyzed in detail. Furthermore, the finite element model of aluminum alloy specimens under low-cycle fatigue loading was established and compared with the experimental results. The effects of specimen parallel length, parallel diameter, and repeated loading patterns on the mechanical properties of aluminum alloys were discussed. The results show that when the specimen is monotonously stretched to fracture, the failure result from shearing break. When the specimen is repeatedly stretched to failure, the fracture of the specimen is a result of the combined action of tensile stress and plastic fatigue damage. The AA6061, AA7075, and AA6063 aluminum alloys all show cyclic softening characteristics under repeated loading. When the initial stress amplitude of repeated loading is greater than 2.5%, the repeated tensile loading has a detrimental effect on the deformability of the aluminum alloy. Finally, based on experiment research as well as the results of the numerical analysis, the calculation method for the tensile strength of aluminum alloys under low-cycle fatigue loading was proposed. [ABSTRACT FROM AUTHOR]

This research was carried out to investigate the influence of Sr-Sb on the microstructures and mechanical properties of Al-18 wt % Mg2Si-4.5Cu alloys. After the addition of 0.2 wt % Sr-Sb, the morphologies of primary Mg2Si transformed from equiaxed dendrite to cube in as-cast alloys and the average size of primary Mg2Si decreased from ~50 to ~20 µm. The shape of eutectic Mg2Si changed from Chinese script to short rod. After extrusion and T6 heat treatment, the ultimate tensile strength of modified alloy at room temperature (RT) and 100 °C increased respectively from 229 to 288 MPa, and from 231 to 272 MPa. The elongation-to-failure only slightly improved from 2.9% to 3.8% and from 3.3% to 3.7% at RT and 100 °C, respectively. The tensile fracture surface revealed a transition from brittle fracture to ductile fracture after modifying by 0.2 wt % Sr-Sb. [ABSTRACT FROM AUTHOR]