Finite element analysis of temperature and stress fields during selective laser melting process of Al−Mg−Sc−Zr alloy

A 3D finite element model was established to investigate the temperature and stress fields during the selective laser melting process of Al−Mg−Sc−Zr alloy.By considering the powder−solid transformation,temperaturedependent thermal properties,latent heat of phase transformations and molten pool convection,the effects of laser power,point distance and hatch spacing on the temperature distribution,molten pool dimensions and residual stress distribution were investigated.Then,the effects of laser power,point distance and hatch spacing on the microstructure,density and hardness of the alloy were studied by the experimental method.The results show that the molten pool size gradually increases as the laser power increases and the point distance and hatch spacing decrease.The residual stress mainly concentrates in the middle of the first scanning track and the beginning and end of each scanning track.Experimental results demonstrate the accuracy of the model.The density of the samples tends to increase and then decrease with increasing laser power and decreasing point distance and hatch spacing.The optimum process parameters are laser power of 325−375 W,point distance of 80−100μm and hatch spacing of 80μm.

Microstructures and mechanical properties of in-situ TiB2/Al−xSi−0.3Mg composites

In-situ 2 vol.%TiB2 particle reinforced Al−xSi−0.3Mg(x=7,9,12,15 wt.%)composites were prepared by the salt−metal reaction,and the microstructures and mechanical properties were investigated.The results show that the TiB2 particles with a diameter of 20−80 nm and the eutectic Si with a length of 1−10μm are the main strengthening phases in the TiB2/Al−xSi−0.3Mg composites.The TiB2 particles promote grain refinement and modify the eutectic Si from needle-like to short-rod shape.However,the strengthening effect of TiB2 particles is weakened as the Si content exceeds the eutectic composition,which can be attributed to the formation of large and irregular primary Si.The axial tensile test results and fractography observations indicate that these composites show more brittle fracture characteristics than the corresponding alloy matrixes.