Sc元素添加对双辊铸轧Al−Cu−Li−Mg−Zr基合金热处理的影响

Effect of Sc addition on downstream processing of twin-roll cast Al−Cu−Li−Mg−Zr-based alloys

提出制备含Sc的Al−Cu−Li−Mg−Zr基合金带材的工艺方案。即先采用双辊铸轧技术制备近净形状的3 mm厚带材,再对其进行均匀化/固溶处理。研究两种Al−Cu−Li−Mg−Zr基双辊铸轧合金,其中一种添加质量分数为0.17%的Sc,另一种未添加Sc。两种合金均先在300℃下退火30 min,然后在450℃下退火30 min以及530℃下退火30 min,随后进行室温水淬。前两段退火后组织中生成了细小、弥散的Al_(3)Zr/Al_(3)(Sc,Zr)颗粒。最后的退火步骤起到了均匀化/固溶处理的作用。双辊铸轧材料的细小晶粒结构使含有主要合金元素的原始颗粒在较短的退火时间内溶解。缩短保温时间可以限制表面层中Li的耗尽和Al_(3)Zr/Al_(3)(Sc,Zr)弥散相的明显粗化。铸态含Sc材料已经具有明显细小的晶粒结构,而经均匀化/固溶处理后生成的Al_(3)(Sc,Zr)弥散相抑制了晶粒在高温下发生粗化。在后续180℃下时效处理后,形成了θʹ(Al_(2)Cu)、T1(Al_(2)CuLi)和S'(Al_(2)CuMg)强化相。在峰值时效状态下,屈服强度提高了200 MPa,这一数值与类似直接冷却铸造材料的相当,从而证实了所提方案的合理性。

A processing scheme for preparing strips of Al−Cu−Li−Mg−Zr-based alloys microalloyed with Sc was proposed.This scheme includes a twin-roll casting of strips with a near-net-shaped 3 mm-thick gauge and a homogenization/solution treatment processing step.Two twin-roll cast Al−Cu−Li−Mg−Zr-based alloys were studied,one with an addition of 0.17 wt.%Sc,and the other without addition of Sc.Both alloys were annealed at 300℃ for 30 min,450℃ for 30 min,and 530℃ for 30 min and quenched into room temperature water.The first two annealing steps provide a fine dispersion of Al3Zr/Al3(Sc,Zr)particles.The final annealing step serves as homogenization/solution treatment.A fine crystallization structure of the twin-roll cast materials enables the dissolution of primary particles containing the main alloying elements during a relatively short annealing time.Shorter soaking duration limits the depletion of surface layers from Li and significant coarsening of Al3Zr/Al3(Sc,Zr)dispersoids.The Sc-containing material has significantly finer grains already in the as-cast state.The Al3(Sc,Zr)dispersoids formed during the homogenization/solution treatment step prevent grain coarsening at high temperatures.Strengtheningθ′(Al_(2)Cu),T1(Al_(2)CuLi),and rare S'(Al_(2)CuMg)phases are formed during subsequent artificial aging at 180℃.The increase in yield strength was 200 MPa in the peak-aged conditions.This value is comparable to the ones reported in similar direct-chill cast materials,thus validating the proposed processing scheme.