退火工艺对AZ31B镁合金铸轧板组织和性能的影响

Effect of annealing process on microstructure and properties of AZ31B magnesium roll-casting alloy sheet

研究不同退火温度、时间对普通铸轧和复合能场（电磁场＋超声波）铸轧AZ31B镁板组织及性能的影响。研究结果表明：铸轧镁板的再结晶温度在复合能场作用下降低了约50℃；250℃退火时，普通铸轧镁板无明显再结晶，复合能场铸轧镁板局部再结晶；在300℃，4h时，铸轧镁板均充分再结晶，复合能场铸轧镁板晶粒细小，组织均匀，平均晶粒直径为8～13μm，而普通铸轧镁板晶粒平均晶粒直径为14～19μm；400℃退火时，晶粒开始粗大，1h时复合能场铸轧镁板与普通铸轧镁板的平均晶粒直径分别为28～33I．μm和20～25μm。退火后，铸轧镁板内析出相数减少，复合能场铸轧镁板析出相弥散分布在晶界上，普通铸轧镁板析出相较多并富集在晶界和晶界附近。退火后铸轧镁板的塑性变形能力明显改善，在300℃，4h时，复合能场铸轧镁板的硬度、抗拉强度、屈服强度、伸长率比普通铸轧镁板分别提高了4．7％，17．2％，34．1％和74．6％。

Effects of general roll-casting and combination of energy-field roll-casting （electromagnetic field and ultrasonic） on the microstructure and properties of AZ31B Mg alloy sheets at different annealing temperatures and time were investigated. The result shows that the recrystallization temperature of Mg roll-casting sheet with the compound energy-field is about reduced by 50 ℃. Annealed at 250 ℃, general Mg roll-casting sheet has no clear recrystallization, compound energy-field Mg roll-casting sheet locally recrystallized; Annealed at 300 ℃, Mg roll-casting sheets are fully recrystallized when holding for 4 h, compound energy-field Mg roll-casting sheet has fine grains and uniform microstructure, the average grains diameter of general Mg roll-casting sheet and compound energy-field Mg roll-casting sheet are respectively 14-19 μm and 8-13 μm; Annealed at 400 ℃, the grains become coarse in a short time, the average grains diameter of general Mg roll-casting sheet and compound energy-field Mg roll-casting sheet are respectively 20-25 μm and 28-33 μm when holding for 1 h. The precipitates of annealed Mg roll-casting sheets are reduced, and the precipitates of general Mg roll-casting sheet with thicker size are enriched on the grain boundaries and at the grain boundaries. The plastic deformation of Mg roll-casting sheets is improved significantly; At 300 ℃ for 4 h, compared to general Mg roll-casting sheet, the hardness, ultimate tensile strength, yield strength and elongation of compound energy-field Mg roll-casting sheet are respectively improved by 4.7%, 17.2%, 34.1% and 74.6%.