Realizing strength-ductility combination of coarse-grained Al0.2Co1.5CrFeNi1.5Ti0.3 alloy via nano-sized, coherent precipitates
Realizing strength-ductility combination of coarse-grained Al0.2Co1.5CrFeNi1.5Ti0.3 alloy via nano-sized, coherent precipitates
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DOI：
10.1016/j.ijplas.2017.10.005
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发表时间：
2018-01-01
影响因子：
9.8
通讯作者：
Wang, Jian
中科院分区：
文献类型：
--
作者：
Ming, Kaisheng;Bi, Xiaofang;Wang, Jian
通过电弧熔炼和1150 ℃固溶退火3 h制备的具有单相面心立方结构（FCC）的粗晶非等原子Al0.2Co1.5CrFeNi1.5Ti0.3固溶体（晶粒尺寸> 1 mm）表现出540 MPa的低屈服强度、917 MPa的极限抗拉强度和50%的断裂伸长率。通过调整时效温度和时间，可以在不明显牺牲塑性的情况下得到强化。利用透射电子显微镜（TEM）的结构表征表明，在700-1000 ℃的温度下时效期间形成纳米尺寸的、球形的、共格的、有序的L1（2）Ni-3（Ti，Al）型沉淀物。固溶退火试样在800 ℃时效1 h ~ 100 h时，L1（2）相的平均直径从约6 nm增加到约50 nm。这些时效合金表现出相似的屈服强度为750 MPa和极限抗拉强度为1160 MPa，但随着时效时间从1 h增加到100 h，断裂伸长率从42%下降到12%。屈服强度和极限抗拉强度的增加，而不明显牺牲延展性后，老化1-5小时归因于均匀分布的，纳米尺寸的，连贯的沉淀物中的粗晶固溶体，其中滑移位错通过纳米尺寸的连贯沉淀物切割。时效时间长导致合金塑性差的原因是大尺寸析出相对位错运动的阻碍作用，导致位错在析出相-基体界面处堆积，滑移位错绕过析出相形成环状，这为开发具有上级强韧性的FCC结构粗晶非等原子合金提供了指导。
Coarse-grained non-equiatomic Al0.2Co1.5CrFeNi1.5Ti0.3 solid solutions (grain size > 1 mm) with single-phase face centered cubic structure (FCC), produced by arc-melting and solution annealing at 1150 degrees C for 3 h, exhibit a low yield strength of 540 MPa, ultimate tensile strength of 917 MPa and elongation to fracture of 50%. By adjusting aging temperature and time, it can be strengthened without apparently sacrificing ductility. Structure characterizations using transmission electron microscopy (TEM) reveal that nano-sized, spherical, coherent, ordered L1(2) Ni-3(Ti,Al)-type precipitates are formed during aging at temperatures of 700-1000 degrees C. The average diameter of L1(2) precipitates increases from similar to 6 inn to similar to 50 nm when the solution annealed specimens are aged at 800 degrees C for 1 h-100 h. These aged alloys exhibit a similar yield strength of 750 MPa and ultimate tensile strength of 1160 MPa but a decreasing elongation to fracture from 42% to 12% in association with the increasing aging time from 1 h to 100 h. The increase in both yield and ultimate tensile strength without apparently sacrificing ductility after aging for 1-5 h is ascribed to uniformly distributed, nano-sized, coherent precipitates in the coarse-grained solid solution, where gliding dislocations cut through nano-sized coherent precipitates. The poor ductility associated with the long aging time is ascribed to the strong barrier of large precipitates to dislocation motion, resulting in dislocations pileups at precipitate-matrix interfaces, where gliding dislocations bypass a precipitate by looping it. These findings provide guidance for developing FCC-structured coarse-grained non-equiatomic alloys with superior strength-ductility combination.