Suppression and reactivation of transformation and twinning induced plasticity in laser powder bed fusion additively manufactured Ti-10V-2Fe-3Al
Suppression and reactivation of transformation and twinning induced plasticity in laser powder bed fusion additively manufactured Ti-10V-2Fe-3Al
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DOI：
10.1016/j.addma.2021.102406
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发表时间：
2021-12-01
影响因子：
11
通讯作者：
Banerjee, R.
中科院分区：
文献类型：
--
作者：
Mantri, S. A.;Nartu, M. S. K. K. Y.;Banerjee, R.
采用激光粉床熔化技术(LBPF)制备了可应变变形的钛合金Ti-10V-2Fe-3Al(wt%)。虽然该合金具有相变诱导塑性(TRIP)，但在拉伸载荷下，即使它表现出相同的β+omega组织，也没有表现出同样的TRIP效应。在LBPF过程中经历了反复的加热-冷却循环，导致了溶质元素(Fe、V和Al)的早期排斥，形成了等温的omega(Omega)析出物，这些析出物是通过结合透射电子显微镜(TEM)和三维原子探针层析(APT)的详细研究而捕捉到的。虽然这些均匀分布的等温欧米伽析出物导致更高的屈服强度，但贝塔基体中的TRIP/TWIP效应受到抑制，导致塑性非常低，几乎没有应变淬透性。有趣的是，在经过简单的贝塔固溶热处理和淬火后，在相同的LPBF Ti-10V-2Fe-3Al合金中，TRIP/TWIP效应被重新激活。该合金表现出显著的拉伸塑性恢复和非常大的应变硬化(拉伸强度减去屈服强度-500兆帕)，具有高的平均应变硬化率-15000。在LBPF处理的Ti-10V-2Fe-3Al的情况下，如此高的应变硬化率似乎是由于在塑性变形的早期阶段由应变诱导的从β到α的快速转变，导致了高体积分数的马氏体相，并伴随着马氏体片内的层状孪晶。
Laser powder bed fusion (LBPF) was employed to fabricate a strain-transformable beta-Ti alloy, Ti-10V-2Fe-3Al (wt %). While the alloy is known to exhibit transformation induced plasticity (TRIP), the as-fabricated alloy, under tensile loading, did not show the same TRIP effects, even though it exhibits the same beta + omega microstructure. The repeated heating-cooling cycles experienced during the LBPF process leads to the early stages of rejection of solute elements (Fe, V, and Al), forming isothermal omega (omega) precipitates, which were captured via detailed investigations coupling transmission electron microscopy (TEM) and three-dimensional atom probe tomography (APT). While these homogeneously distributed isothermal omega precipitates lead to a higher yield strength, the TRIP/TWIP effects within the beta matrix were suppressed, leading to very low ductility and virtually no strainhardenability. Interestingly, after a simple beta-solution heat treatment followed by quenching, leading to a beta + omega (athermal) microstructure, the TRIP/TWIP effects were reactivated in the same LPBF Ti-10 V-2Fe-3Al alloy. The alloy exhibited substantial recovery of tensile ductility and a very large strain hardening (tensile strength minus yield strength -500 MPa), with a high average strain hardening rate -15000. Such a very high strain hardening rate in case of LBPF processed Ti-10 V-2Fe-3Al, appears to arise from a rapid strain-induced transformation from beta to alpha" at the early stages of plastic deformation, leading to a high-volume fraction of the martensitic phase, coupled with hierarchical twinning within the martensite plates.