轧制工艺对7050铝合金显微组织和力学性能的影响

EFFECTS OF ROLLING PROCESS ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF 7050 ALUMINUM ALLOY

研究了轧制变形量和轧制温度对7050铝合金显微组织和力学性能的影响.当轧制变形量为30%时,轧制样品中大部分晶粒还基本保持铸态的枝晶形状;当变形量在70%以上时,铸态组织完全消失,并出现再结晶晶粒和亚晶组织.能谱结果表明,轧制样品中粗大的第二相为Al_7Cu_2Fe和Al_2CuMg,Al_7Cu_2Fe相不溶于基体且呈链状分布,而Al_2CuMg相部分溶于基体且呈球状分布.变形量为70%和90%样品的再结晶晶粒分数分别为1.25%和12.4%.变形量为70%样品的强度和硬度最高.当轧制温度为300℃时,时效后的样品中出现较多的再结晶晶粒;轧制温度升至430℃时,材料流变性变好,并且在轧制过程中更容易发生动态回复,使储存的变形能减少,再结晶晶粒明显减少,强度和硬度也达到最高.

The effects of rolling reduction and temperature on the microstructure and mechanical property of 7050 aluminum alloy are investigated. For the sample with a rolling deformation of 30%, most of dendritic structure remained. When the rolling reduction increased to the 70%, the cast structure disappeared and the microstructure consisted of subgrains and recrystallized grains. Some coarse particles were identified to be Al7Cu2Fe phase and Al2CuMg phase by EDS. The Al7Cu2Fe particles with a chain-like distribution did not dissolve into the matrix, whereas the globular-like Al2CuMg phase was partially dissolved during the heat treatment. The fractions of the recrystallized grains in the samples rolled under reductions of 70% and 90% are 1.25% and 12.4%, respectively. The sample rolled under a rolling reduction of 70% exhibited the highest strength and hardness. The sample rolled at 300 ℃ has a lot of recrystallized grains. At 430℃rolling, both of the improvement of material flow and the occurrence of dynamic recovery reduced the stored deformation energy, inducing the amount of recrystallized grains decreased, so the sample exhibited the highest strength and hardness.