激光立体成形技术逐点逐层的成形方式, 特别适合构件化学成份及显微组织在空间呈现特定分布的梯度材料的成形。本文利用激光立体成形技术, 以不同质量分数配比TA15-xTi2AlNb(x=0%, 20%, 40%, 60%, 80%, 100%)混合粉末为原材料, 制备了线性过渡型TA15-xTi2AlNb梯度材料, 研究了梯度材料随着Ti2AlNb含量的增加, 宏微观组织的演化规律及梯度区成份、显微硬度变化规律。研究发现Ti2AlNb的添加对梯度材料宏观晶粒形态影响显著: TA15钛合金部分为外延生长的粗大柱状晶; TA15-20%Ti2AlNb部分底部为外延生长的短柱状晶, 中部发生CET转变, 顶部为近等轴晶; 梯度材料其余部分均由等轴晶组织组成。显微组织方面, 在梯度区内, 随着Ti2AlNb含量的增加, 各成份段组织演化依次为: α+β网篮组织→α+β网篮+次生α′→短针状α+β→大块状α+β→细小α2+B2/β→O+α2+B2; 同时, 显微组织尺寸呈现出先增大后突然增大、又逐渐减小的趋势, 该规律与维氏硬度平均值变化规律相反。

The shaping principle of laser solid forming of point by point, layer by layer though melting and solidification of metal powders offers distinct advantage over conventional manufacturing methods to manufacture graded materials or dual alloy that chemistry and microstructure varying spatially within the component. TA15-Ti2AlNb graded material (GM) was fabricated by laser solid forming using TA15-xTi2AlNb(x=0%, 20%, 40%, 60%, 80%, 100%)mixed powders. The macrostructure and microstructure evolution of TA15-Ti2AlNb FGM with the increasing of Ti2AlNb content were investigated, compositional distribution and micro-hardness evolution also were studied. The results show that grain morphology within FGM was affected significantly by the addition of Ti2AlNb: the macrostructure of TA15 are consisted of coarsen columnar prior β grains that grew epitaxially through many cladding layers; the microstructure at bottom of TA15-20% Ti2AlNb region contains short columnar grains and near equiaxed grains at top, obvious CET (columnar to equiaxed transition) were happened at middle region; the other parts of GM are composed of equiaxed grains. In respect of microstructure within graded region, with the increasing of content Ti2AlNb such an evolution can be observed in sequence: α+β basket wave microstructure → α + β basket wave +fine secondary α′ phase →short rod-like α + β →large blocked α + β → fine α2 +B2/β → O + α2 + B2. Meanwhile, a trend of increasing firstly then decreasing abruptly and increasing gradually again was presented for microstructure size, which was contrary to variation of average Vickers hardness, in other words, the fine microstructure lead to a high hardness value.