On the effect of scan strategies on the transformation behavior and mechanical properties of additively manufactured NiTi shape memory alloys
On the effect of scan strategies on the transformation behavior and mechanical properties of additively manufactured NiTi shape memory alloys
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DOI：
10.1016/j.jmapro.2022.09.051
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发表时间：
2022-10-14
影响因子：
6.2
通讯作者：
Elwany, Alaa
中科院分区：
文献类型：
--
作者：
Zhang, Chen;Ozcan, Hande;Elwany, Alaa
激光-粉末床熔融（L-PBF）增材制造（AM）呈现出从镍钛形状记忆合金（NiTi SMA）制造具有定制微观结构和成分的几何复杂结构的优异潜力。常见的L-PBF工艺参数，如激光功率，扫描速度和舱口间距的影响，已在许多文献研究中报道。然而，尚未研究的一个重要因素是激光扫描策略，或激光在每层内遵循的路径。这是一个特别重要的因素，调查的情况下，NiTi SMA往往是更敏感的热历史比其他商业AM材料。例如，由于镍的不同蒸发导致的成分变化，热历史中即使微小的变化也可能对转变行为表现出显著的影响。目前的工作提出了第一次调查的12激光扫描策略的增材制造的富镍NiTi SMA的制造结果的影响。不同扫描策略下的制件翘曲变形程度和表面形貌存在显著差异。不同的扫描策略之间的一些相变变化也被确定在制造和固溶热处理的条件下，虽然这些变化是不明显的翘曲变形，由于残余应力和表面形态的变化。本研究指导扫描策略的选择，以尽量减少由于过度翘曲和不良表面形态导致的构建失败。它还在控制这种相对难以加工的材料类别的机械性能和相变行为方面提供了额外的灵活性。
Laser-powder bed fusion (L-PBF) additive manufacturing (AM) presents excellent potential to fabricate geometrically complex structures with tailored microstructures and compositions from nickel titanium shape memory alloys (NiTi SMAs). The effect of common L-PBF process parameters, such as laser power, scanning speed, and hatch spacing, have been reported in many literature studies. However, one important factor that has not been investigated is the laser scan strategy, or the path that the laser follows within each layer. This is a particularly important factor to investigate in the case of NiTi SMAs that tend to be more sensitive to thermal histories than other commercial AM materials. For example, even slight variations in thermal history might exhibit notable influence on transformation behavior due to composition changes resulting from differential evaporation of nickel. The current work presents a first investigation on such effects of 12 laser scan strategy on the fabrication outcome of additively manufactured Ni-rich NiTi SMAs. The extent of warping deformation and surface morphology of fabricated parts with different scan strategies were found to show notable differences. Some phase transformation variations among different scan strategies were also identified in as-fabricated and solution heat treated conditions, although these variations were not as pronounced as variations in warping due to residual stresses and surface morphology. This study guides the selection of scan strategies such that build failures due to excessive warping and poor surface morphology are minimized. It also provides additional flexibility in controlling mechanical properties and phase transformation behavior of this relatively difficult-to -process class of materials.