Kunyuan Gao

The Microstructure Evolution of Al–Mg–Si–Mn–Er–Zr Alloy During Homogenization

The formation of non-equilibrium intermetallic phases during solidification significantly deteriorates the mechanical properties of Al–Mg–Si–Mn–Zr–Er alloy, but homogenization heat treatment can effectively reduce these residual phases. Therefore, it is necessary to study the evolution of these non-equilibrium intermetallic phases during different homogenization treatment. In this study, the methods we used are OM, SEM in combination with EDS, XRD and TEM. The results showed that non-equilibrium intermetallic phases between grains are mainly Al0.5Fe3Si0.5, Al0.7Fe3Si0.3 and Al5Mn12Si7. After homogenization, the main residual phase is Al5Mn12Si7. Compared with single homogenization, two-stage homogenization can effectively reduce the homogenization time and is good for the precipitation of fined Al3(Er, Zr) particles.

Effect of Erbium–Zirconium Composite Modifications on the Microstructure and Mechanical Properties of A356 Aluminum Alloy

The Al–7Si–0.3 Mg (A356) alloys with various contents of the rare earth element Er, Zr were prepared by the conventional casting technique. The effect of Er, Zr composite modifications on the microstructure and mechanical properties of A356 alloys was investigated using the optical microscopy (OM), scanning electronic microscopy (SEM), energy spectrum analysis and mechanical testing. The results show that addition of 0.3 wt% Er and Zr had an excellent refining effect on α-Al grains and a modification effect on Si containing phase in the as-cast state. The size of α-Al dendrite reduced, the acicular eutectic Si became short rod-shaped or granular. When Er and Zr content was 0.3 wt%, the tensile strength and hardness of the alloys reached up to maximum values.

Microstructure and Mechanical Properties of Hot-Rolled 5E83 Alloy

Hot-rolling plates of Al–4.5Mg–0.7Mn–0.2Zr–0.2Er alloy were prepared under the reduction of 50%, and tensile property, impact toughness were measured at the temperatures varying from 200–470 °C. The microstructure of the hot-rolling plates was investigated using scanning electron microscopy and transmission electron microscopy. The results showed that the tensile strength and yield strength decreased with the rise of the hot-rolling temperature, the elongation and impact toughness showed the opposite trend, and the best match between strength and toughness was at the rolling temperature of 350 °C. The second phase particles in the alloy had a great influence on the impact toughness and plasticity of the alloy. As the rolling temperature increased, the dynamic recovery and dynamic recrystallization occurred in the alloy. Dispersed Al3(Er, Zr) particles formed in the alloy when Er and Zr were added. The Al3(Er, Zr) particles were able to pin dislocation motion, hinder the growth of subgrains and the migration of grain boundaries, thereby inhibited the dynamic recrystallization of Al–4.5Mg–0.7Mn–0.2Zr–0.2Er alloy and its thermal stability improved.

Effect of RRA Treatment on the Properties and Microstructural Evolution of Al–Zn–Mg–Cu–Er–Zr Alloy

Effect of RRA treatment on the mechanical properties and microstructure of Al–Zn–Mg–Cu–Er–Zr aluminium alloy was researched by hardness measurement, conductivity measurement, exfoliation corrosion measurement, transmission electron microscopy (TEM). Discussed the relationship between the regression treatment and composite properties of the alloy. The study found that the hardness of RRA treated alloys first rise and then decline with the increasing of regression time, but the corrosion performance is increasing all the time. After pre-aging treatment 120 °C/24 h, regression treatment 180 °C/60 min, re-aging treatment 120 °C/24 h, the combination property of the alloy is optimal, the hardness, conductivity and the exfoliation corrosion grade are respectively: 207.6 HV, 33.53%IACS, PC. At this moment, it is found from the TEM observations that the matrix precipitates are small and dispersed, resemble to T6 temper. The grain boundary precipitation out phases are discontinuous distribution and the relatively wider PFZ, similar to the T73 temper.