退火工艺对轧制半固态坯料组织性能的影响

Effect of Annealing Process on Microstructure and Properties of Rolled Semi-solid Billet

采用异步轧制工艺对7075铝合金半固态坯料进行形变热处理。研究了再结晶退火工艺对变形半固态板材的组织演变及力学性能的影响。重点分析了各工艺参数条件下获得退火板材的再结晶程度及晶粒尺寸变化趋势,梳理了变形半固态板材退火过程中的再结晶机制。结果表明:显微组织的再结晶顺序依次为变形共晶相、变形初生固相、变形晶内小“液滴”。当退火工艺参数为470℃保温20 min时,退火板材的再结晶晶粒尺寸较小,综合力学性能较优,此退火板材的抗拉强度和延伸率依次为408 MPa、28%。退火温度的升高将导致板材由脆性断裂向韧性断裂方式转变,但过高的退火温度将引起板材的热裂,将极大地降低板材的力学性能。

Deformation heat treatment of 7075 aluminum alloy semi-solid billet was carried out by asynchronous rolling process.The effect of recrystallization annealing on microstructure evolution and mechanical properties of the deformed semi-solid sheets was studied.The recrystallization degree and grain size change trend of the annealed sheet under various process parameters were analyzed,and the recrystallization mechanism of the deformed semi-solid sheet during annealing was summarized.The results show that the recrystallization order of microstructure is deformed eutectic phase,deformed primary solid phase,and deformed intragranular “droplet”.When the annealing process is held at 470 ℃ for 20 min,the recrystallized grain size of the annealed sheet is smaller and the comprehensive mechanical properties are better.The tensile strength and elongation of the annealed sheet are 408 MPa and 28%,respectively.The increase of annealing temperature will lead to the transition from brittle fracture to ductile fracture,but too high annealing temperature will lead to hot cracking,which will greatly reduce the mechanical properties of the plate.