Tanrikulu Ahmet Alptug, Farhang Behzad, Ganesh-Ram Aditya, Hekmatjou Hamidreza, Durlov Sadman Hafiz, Amerinatanzi Amirhesam
Materials Science and Engineering, The University of Texas at Arlington, Arlington, TX 76019, USA.
Turkish Aerospace Industries, Ankara 06980, Türkiye.
Materials (Basel). 2024 Apr 22;17(8):1929. doi: 10.3390/ma17081929.
An innovative in situ thermal approach in the domain of LPBF for Ti-6Al-4V fabrication has been carried out with results directing towards an improved fatigue life without the need for post-processing. The thermal process involves an additional laser scan with different process parameters to preheat the selected regions of each layer of the powder bed prior to their full melting. This preheating step influences the cooling rate, which in turn affects surface characteristics and subsurface microstructure, both of which are directly correlated with fatigue properties. A thorough analysis has been conducted by comparing the preheated samples with reference samples with no preheating. Without any additional thermal processing, the preheated samples showed a significant improvement over their reference counterparts. The optimized preheated sample showed an improved prior β-grain distribution with a circular morphology and thicker α laths within the even finer prior β-grain boundaries. Also, an overall increment of the c/a ratio of the HCP α has been observed, which yielded lattice strain relaxation in the localized grain structure. Furthermore, a less-profound surface roughness was observed in the preheated sample. The obtained microstructure with all these factors delivered a 10% improvement in its fatigue life with better mechanical strength overall.
在用于制造Ti-6Al-4V的激光粉末床熔融（LPBF）领域，已经开展了一种创新的原位热方法，其结果表明无需后处理即可提高疲劳寿命。该热过程包括使用不同的工艺参数进行额外的激光扫描，以便在每层粉末床完全熔化之前预热选定区域。这个预热步骤会影响冷却速率，进而影响表面特性和亚表面微观结构，而这两者都与疲劳性能直接相关。通过将预热样品与未预热的参考样品进行比较，进行了全面分析。在没有任何额外热处理的情况下，预热样品相对于其参考样品表现出显著改善。优化后的预热样品显示出先前β晶粒分布得到改善，呈圆形形态，并且在更细的先前β晶粒边界内α板条更厚。此外，还观察到密排六方（HCP）α的c/a比总体增加，这在局部晶粒结构中产生了晶格应变弛豫。此外，在预热样品中观察到表面粗糙度较低。考虑到所有这些因素所获得的微观结构，其疲劳寿命提高了10%，整体机械强度也更好。
