Mendoza Michael Y, Samimi Peyman, Brice David A, Ghamarian Iman, Rolchigo Matt, LeSar Richard, Collins Peter C
1Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 USA.
Center for Advanced Non-Ferrous Structural Alloys (CANFSA), Ames, USA.
BMC Chem. 2019 Jan 29;13(1):5. doi: 10.1186/s13065-019-0529-3. eCollection 2019 Dec.
Laser Engineered Net Shaping (LENS™) was used to produce a compositionally graded Ti-xMo (0 ≤ x ≤ 12 wt %) specimen and nine Ti-15Mo (fixed composition) specimens at different energy densities to understand the composition-processing-microstructure relationships operating using additive manufacturing. The gradient was used to evaluate the effect of composition on the prior-beta grain size. The specimens deposited using different energy densities were used to assess the processing parameters influence the microstructure evolutions. The gradient specimen did not show beta grain size reduction with the Mo content. The analysis from the perspective of the two grain refinement mechanisms based on a model known as the Easton & St. John, which was originally developed for aluminum and magnesium alloys shows the lower bound in prior-beta grain refinement with the Ti-Mo system. The low growth restriction factor for the Ti-Mo system of = 6,5C explains the unsuccessful refinement from the solute-based mechanism. The energy density and the grain size are proportional according to the results of the nine fixed composition specimens at different energy densities. More energy absorption from the material represents bigger molten pools, which in turn relates to lower cooling rates.
采用激光工程净成形技术（LENS™）制备了成分梯度Ti-xMo（0≤x≤12 wt%）试样以及九个不同能量密度下的Ti-15Mo（固定成分）试样，以了解增材制造过程中的成分-工艺-微观结构关系。利用该成分梯度来评估成分对原始β晶粒尺寸的影响。使用不同能量密度沉积的试样用于评估工艺参数对微观结构演变的影响。梯度试样并未表现出随着Mo含量增加β晶粒尺寸减小的情况。基于最初为铝和镁合金开发的伊斯特顿和圣约翰模型，从两种晶粒细化机制的角度进行分析，结果表明Ti-Mo体系在原始β晶粒细化方面存在下限。Ti-Mo体系的低生长限制因子（= 6.5C）解释了基于溶质机制的细化未成功的原因。根据九个不同能量密度下固定成分试样的结果，能量密度与晶粒尺寸成正比。材料吸收更多能量意味着熔池更大，进而与更低的冷却速率相关。
