Distribution and evolution of aging precipitates in Al-Cu-Li alloy with high Li concentration

The evolution and distribution of the aging precipitates in 1460 Al-Li alloy with high Li concentration (2.14%, mass fraction) during T6 aging and two-step T8 (4% predeformation) aging were investigated through TEM. The aging precipitates include δ'(Al3Li) and T1 (Al2CuLi) phases, of which the δ' phases are formed first in grain interiors. A lot of δ'/GPI/δ' composite precipitates in which GPI zones are flanked with a pair of δ' phases, are formed at 145℃ of T6 aging, which are thermally stable. At 160℃ and 175℃ of T6 aging, many T1 phases nucleate first at subgrain boundaries and grain boundaries, and then form and grow within grains. As to the T8 aging, the δ'/GPI/δ' composite precipitates are formed during the first-step aging at 130℃ for 20 h, which are thermally stable during the second-step aging at 160℃. The plastic predeformation accelerates T1 nucleation within grains during the second-step aging at 160℃.

新型超高强铝锂合金厚板厚度方向组织及性能的不均匀性

以一种40 mm厚度新型超高强铝锂合金(Al-3.76Cu-1.3Li-0.11Zr-0.42Mg-0.44Ag-0.38Zn-0.28Mn-0.05Ti)板材为对象,研究了其T8时效态(压缩预变形6%,温度150℃)厚度方向上室温纵向拉伸力学性能和组织的不均匀性。结果表明:时效初期(5 h),厚板表层强度(抗拉强度为499 MPa)略高于T/2层(抗拉强度为461 MPa)。而时效16~96 h后,厚板T/2层的屈服强度和抗拉强度均高于表层,并且强度差保持在55MPa左右。峰时效时T/2层抗拉强度为668 MPa,表层抗拉强度为611 MPa。厚板表层和T/2层纵截面固溶态的晶粒组织呈长条状,沿轧制方向被拉长。表层织构总体积分数为48.9%,主要由变形织构(Brass{011}<211>织构、S{123}<634>织构和Cu{112}<111>织构,总体积分数达45.6%)组成;而T/2层织构总体积分数较表层高(73.1%),主要由变形织构(39.6%)和较多的再结晶织构(Goss{011}<100>织构和Cube{001}<100>织构,总体积分数为33.5%)组成。合金厚板T8时效析出相包括T1相(Al2CuLi),θ′相(Al2Cu)和δ′相(Al3Li)。与表层相比,时效24 h时厚板T/2层析出的T1相数量较多,而θ′相数量较少。