初始晶粒形貌对热等静压LPBF-Inconel 738合金微观组织和力学性能各向异性的影响

Effects of Initial Grain Morphology on Anisotropy of Microstructure and Mechanical Property in LPBF-Inconel 738 Alloy by Hot Isostatic Pressing

摘要:

通过对不同扫描策略下激光粉末床熔融（laser powder bed fusion，LPBF）成形Inconel 738合金进行热等静压（HIP）处理，研究初始晶粒形貌对HIP处理后Inconel 738合金微观组织及性能各向异性的影响。结果表明，初始晶粒形貌具有很强的遗传性，扫描策略90°成形Inconel 738（as-built 90）合金试样初始晶粒形貌为长柱状晶和不规则细晶，经过HIP处理后（HIP 90）试样的再结晶晶粒形貌为长柱状晶晶粒和少部分等轴晶，而扫描策略67°成形Inconel 738合金试样（as-built 67）初始晶粒形貌为短柱状晶和等轴晶，经过HIP处理后（HIP 67）试样的再结晶晶粒形貌为类等轴晶和等轴晶晶粒。主要原因是初始晶粒形貌决定了应变分布情况，As-built 90合金试样的应变分布呈“条”状，而As-built 67合金试样的应变分布呈“网”状，应变分布较均匀。HIP处理过程中，应变集中区域为再结晶晶粒优先提供了形核位置，从而决定了HIP试样中的再结晶晶粒形貌。HIP 90合金试样的力学各向异性较HIP 67合金试样的力学各向异性更大，主要与HIP 90合金试样长柱状晶晶粒形貌有关。HIP处理后LPBF-Inconel 738合金获得等轴晶晶粒形貌需要配合合适的LPBF工艺参数。

Abstract:

Effects of initial grain morphology on anisotropy of microstructure and mechanical property in Inconel 738 alloy prepared by laser powder bed fusion (LPBF) under different scanning strategies after hot isostatic pressing (HIP) treatment were studied. The results show that the initial grain morphology is highly heritable. The initial grain morphology of Inconel 738 alloy formed by scanning strategy 90° (As-built 90 alloy) presents elongated columnar grains and irregular fine grains. After HIP treatment, the recrystallized grain morphology of HIP 90 alloy presents elongated columnar grains and a few equiaxed grains. The As-built Inconel 738 alloy formed by scanning strategy 67° (As-built 67 alloy) initially has short columnar and equiaxed grains, and the recrystallized grain morphology of HIP 67 samples shows similarly equiaxed and equiaxed grain morphology. The main reason is that the initial grain morphology determines the strain distribution. The strain distribution of As-built 90 samples is in the shape of “bar”, while that of As-built 67 samples is in the shape of “net”, and the strain distribution is more uniform. During HIP treatment, the strain concentration region preferentially provides nucleation location for recrystallized grains, which determines the morphology of recrystallized grains in HIP samples. The mechanical anisotropy of HIP 90 alloy is larger than that of HIP 67 alloy, which is mainly related to the grain morphology of HIP 90 alloy. The equiaxed grain morphology of LPBF-Inconel 738 alloy after HIP treatment requires appropriate LPBF process parameters.