7A04表面纳米化组织的热稳定性

Thermal stability of surface nanocrystalline microstructure of 7A04 aluminum alloy

用旋转辊压塑性变形方法在7A04铝合金表层获得纳米晶组织,用DSC和透射电镜研究了表面纳米晶组织的热稳定性。DSC测试结果表明7A04铝合金表面纳米晶的再结晶温度在473K左右,透射电镜分析表明表面纳米化样品473K退火后晶粒没有明显长大,平均晶粒尺寸约100nm。旋转辊压变形160min,表面层显微硬度由160HV升高到335HV,473K退火后显微硬度下降至250HV,但仍高于基体,573K退火后从表层到基体的显微硬度均明显下降。结果表明7A04表面纳米化组织的使用温度在473K以下。

The surface nanocrystalline microstructure of 7A04 aluminum alloy was obtained by means of circulation rolling plastic deformation （CRPD）. The thermal stability of surface nanocrystalline microstructure was investigated by differential scanning calorimetry （DSC） and transmission electron microscopy （TEM）. The result of DSC shows that the recrystallization temperature is approximately 473K. TEM observation shows that nanocrystallization grain did not grow obviously after annealing at 473K with an average grain size of approximately 100nm. Microhardness of the top surface layer increases fi＇om 160HV to 335HV after CRPD 160min, which is 250HV after annealing at 473K. Microhardness decreases obviously fi＇om matrix to surface after annealed at 573K. All the experimental results indicate that the best application temperature of 7A04 nanocrystallization surface is below 473K.