Quench sensitivity of Al-Cu-Mg alloy thick plate

The quench sensitivity of Al-Cu-Mg alloy was investigated at different thicknesses of the thick plate.The quenching process was simulated via finite element analysis(FEA);time-temperature-property(TTP)curves and time-temperature-transformation(TTT)curves were obtained through hardness test and differential scanning calorimetry(DSC)test;and the microstructural observation was carried out by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Experimental results exhibit that the quench cooling rate decreases dramatically from the surface to the center of the plate,and the inhomogeneous quenching causes the difference in microstructure.With the decrease in quench cooling rate,constituent particles are coarsening gradually;the quantity of T-phase(Al_(20)Cu_(2)Mn_(3))increases and the S-phase(Al_(2)Cu Mg)decreases.According to the precipitation kinetics analysis,the decrease in S-phase is caused by the increase in precipitate activation energy.So that the center of the plate shows the highest quenching sensitivity,which is consistent with the analysis of time-temperature-property curves and time-temperature-transformation curves.

Hardness, quench sensitivity, and electrical conductivity of 7xxx Al alloys with high Zn concentrations

In this study,7 xxx(Al-Zn-Mg-Cu)alloys with high Zn concentrations were fabricated by increasing the Zn contents of 7085 Al alloys.The hardness,quench sensitivity,and electrical conductivity of the alloys and a 7085 Al alloy under peak-aged state were studied.The high Zn concentration alloys had higherη′phase densities and lower quantities of Mg solid atoms than the 7085 Al alloy and thus exhibited higher hardness and electrical conductivity.The high Zn concentration alloys also exhibited slightly higher quench sensitivity than 7085 Al alloy,and the depth of the quenching layer of the alloy with 11.27 wt%Zn content reached 100 mm.This work confirmed that the novel 7 xxx alloy with high Zn concentration showed balanced performance,exhibiting enhanced hardness and conductivity and reasonable quench sensitivity compared with the 7085 commercial Al alloy.

Quench sensitivity of novel Al-Zn-Mg-Cu alloys containing different Cu contents

The effect of copper content on quench sensitivity in novel Al-Zn-Mg-Cu alloys containing high zinc content was investigated by Jominy end quench test.Electrical conductivity and hardness test,temperature collecting,and transmission electron microscopy(TEM)technique were adopted for the properties and microstructure characterization of three alloys with different copper contents.The results indicate that the electrical conductivity of all three alloys increases with the increase of distance from the quenched end,while the hardness shows an opposite trend.If the dropping of 10%hardness is defined as the critical evaluation standard of quenching,the depth of quenched layer of AlloysⅠ,Ⅱ,andⅢare 70,55,and 40 mm,respectively.The precipitation behavior on grain boundaries of three alloys is similar except for a little difference in size,while the size of precipitates in grains of AlloyⅢwith higher copper content is larger than those of the other two alloys at the same location.Considering all results,the stability of the supersaturated solid solution of AlloyⅢis lower than those of the other two alloys,meaning that AlloyⅢshows the highest quench sensitivity.Higher copper content leads to higher quench sensitivity in novel Al-Zn-Mg-Cu alloys with the same content of magnesium,zinc,and other trace elements.