Aluminum alloys are widely used as first-choice materials for lightweight automotive applications. It is important that an alloy have a balance between strength and formability. In this study, the alloys were melted, cast, hot rolled, and cold rolled into 1 mm-thick sheets. The microstructure, mechanical properties, and precipitation behavior of Al–Mg–Si–1.0 wt %-Zn alloys with Mg/Si ratios of 0.5, 1, and 2 after solution treatment were studied using optical and electron microscopy, a tensile test, the Vickers hardness test, and differential scanning calorimetry. The results showed that a high density and number of Al–Fe–Si particles were observed in the matrix, thus causing the formation of more homogeneous and smaller recrystallized grains after treatment with the solution. In addition, a higher volume fraction of cube_ND and P-types texture components formed during solution treatment. Also, a high r value and excellent deep drawability were achieved in the medium-Mg/Si-ratio alloy. The formation of denser strengthening precipitates led to a better paint-bake hardening effect in comparison with the other two alloys. Furthermore, the precipitation kinetics were enhanced by the addition of Si, and the addition of Zn did not alter the precipitation sequence of the Al–Mg–Si alloy. The dual-phase strengthening effect was not achieved in the studied alloys during paint-bake treatment at 175 °C.

In order to optimize the hot working technology of Incoloy 800H,the dynamic recrystallization(DRX) behavior of Incoloy 800H at temperatures ranging from 850°C to 1100°C and strain rates from 0.01 s~(-1) to 10 s~(-1) was investigated by single-pass compression tests on MMS- 300 thermo-mechanical simulator.The evolutions of microstructure and nucleation mechanisms of DRX were analyzed combined with the technique of EBSD and TEM.The results show that when the deformation temperature is below 950°C,the behavior of DRX is obviously restrained by precipitation of Cr_(23)C_6 and Ti(C,N).Therefore the hot deformation constitutive equations in two temperature intervals(from 850°C to 950°C and from 950℃to 1100°C) were established by regression analysis with the deformation activation energy of 465.394 kJ/mol and 427.360 kJ/mol respectively.The inflection points were determined by fitting a third order polynomial to the lnθ-εcurves,which makes the prediction for the ratios of critical stress to peak stress and critical strain to peak strain more accurately. Accordingly,the mathematical models of critical stress and critical strain vs Z parameter were deduced.The DRX nucleation mechanisms of Incoloy 800H during hot deformation mainly include strain induced grain boundary migration,grain fragmentation and subgrain coalescence.