Graphene-reinforced aluminum matrix composites (GRAMCs) attract great interest in industries due to their high performance potential. High-temperature processes such as sintering and aging are usually applied during the preparation of GRAMCs, leading to grain coarsening that significantly influences its properties. In this work, a modified 3D Monte Carlo Potts model was proposed to investigate the effect of content and size of graphene on the grain evolution during the heat treatment of GRAMCs. Grain growth with graphene contents from 0.5 wt.% to 4.5 wt.% and sizes from 5 μm to 15 μm were simulated. The grain growth process, final grain size and morphology of the microstructure were predicted. The results indicated that both the content and size of the reinforcements had an impact on the grain evolution. The pinning effect of grain size can be enhanced by increasing the content and decreasing the size of graphene. Agglomeration and self-contacting phenomena of the graphene arose obviously when the contents and sizes were relatively high. The average grain size decreased by 48.77% when the content increased from 0.5 wt.% to 4.5 wt.%. The proposed method and predicted regulations can provide a reference for the design and fabrication of GRAMCs.

Hot stamping is an important manufacturing process for sheet metal parts. However, it is easy to produce defects such as thinning and cracking in the drawing area during the stamping process. In this paper, the finite element solver ABAQUS/Explicit was used to establish the numerical model of the magnesium alloy hot-stamping process. The stamping speed (2~10 mm/s), the blank-holder force (3~7 kN), and the friction coefficient (0.12~0.18) were selected as the influencing factors. Taking the maximum thinning rate obtained through simulation as the optimization objective, the response surface methodology (RSM) was applied to optimize the influencing factors in sheet hot stamping at a forming temperature of 200 °C. The results showed that the maximum thinning rate of sheet metal was most influenced by the blank-holder force, and the interaction between the stamping speed and the blank-holder force/friction coefficient had a great influence on the maximum thinning rate. The optimal value of the maximum thinning rate of the hot-stamped sheet was 7.37%. Through the experimental verification for the hot-stamping process scheme, the maximum relative error between the simulation and the experimental results was 8.72%. This proves the accuracy of the established finite element model and the response surface model. This research provides a feasible optimization scheme for the analysis of the hot-stamping process of magnesium alloys.