采用激光立体成形技术制备了从Ti到Ti2AlNb成分连续渐变、外形规则、高度为17 mm的梯度材料. 分析了梯度材料的组织及相结构演变规律和硬度变化规律. 随着Al和Nb成分的提高,Ti-Ti2AlNb功能梯度材料的相呈现α' → α+β → α+α' → α' → α+β → α+β/B2+α2 → β/B2+α2 → β/B2 →B2+ α2+O→ B2的演变过程, 实现了由$α$型钛合金经过α+β型及β型钛合金向Ti2AlNb基合金的转变. 硬度值HV从底部纯Ti的170连续 渐变到顶端Ti2AlNb的470. 基于钛合金富Ti区非平衡相图, 并结合Al和Nb元素在钛合金中对α, β和α2稳定性的影响分析, 对梯度材料在激光立体成形过程中的相演化过 程进行了解释.
A functionally graded Ti-Ti2AlNb alloy, which had continuous compositional gradient and regular outline with a length of ~17 mm, was fabricated by laser solid forming. Phase morphological evolution and microstructure evolution, and microhardness along the compositional gradient direction were analyzed. With the increase of aluminum and niobium contents, a series of phase evolutions along the compositional gradient occurred: α'→α+β→α+α'→α'→α+β→ α+β/B2+α2→ β/B2+α2→ β/B2→ B2+α2+O→ B2, and the compositionally graded material accomplished a transition of α titanium alloy, α+β titanium alloy, β titanium alloy, finally ended with Ti2AlNb-based alloy. In the transition layers, The microhardness increased from 170HV with CP titanium at the bottom to 470HV with Ti2AlNb at the top. Based on the non-equilibrium phase diagram of the Ti-rich corner, the phase morphological evolution during laser solid forming of the graded materials were explained on combining with the analysis of the influence of the Al, Nb on the stability of α，β and α2 phases in titanium alloys.
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