高功率及快速扫描对选择性激光熔覆制备Ti-6Al-4V-TiB_w显微结构和力学性能的影响
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摘要
在Ti-6Al-4V(TC4)中添加质量分数为3%的Ti B_2,通过选择性激光熔覆技术(SLM)制备TC4/TiB_w复合材料。采用X射线衍射仪(XRD)分析样品的相成分,利用扫描电镜(SEM)配合能谱仪(EDS)观察样品的表面形貌以及特定区域的元素组成,采用维氏硬度仪对材料测试显微硬度,纳米压痕测试特定组织的弹性模量。实验结果表明:在激光功率高、扫描速度快的条件下,晶粒得到细化出现亚晶胞,试样中的相主要以α-Ti形式存在,并且有新的B化物生成,观察到有未完全熔化的Ti-6Al-4V颗粒存在。力学性能测试表明,与传统的铸造工艺相比,本实验中材料的弹性模量(147 GPa)和显微硬度(500～600 HV)都有显著提高。
TC4 titanium matrix composites composed with 3wt%Ti B_2powders were produced by SLM technology to produce Ti-6Al-4V/TiB_w.X-ray diffraction was used to investigate the phase composition.The microstructure and elements of a particular region were examined by using scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)respectively Meanwhile,nanoindentation and micro-hardness techniques were applied to test the mechanical properties of the Ti-6Al-4V/Ti B_wbulk.The results show that the main phase exists in the form ofα-Ti based on high laser power and fast scanning speed.Rapid cooling rate inhibites grain growth leading to generate a large number of fine grain structures.While a small quantity of unmelted Ti-6Al-4V powders lie on the matrix.The mechanical performance shows that the elastic modulus at 147 GPa and microhardness at 500-600 HV of the samples in this experiment have improved significantly compared with conventional cast TC4.
TC4 titanium matrix composites composed with 3wt%Ti B_2powders were produced by SLM technology to produce Ti-6Al-4V/TiB_w.X-ray diffraction was used to investigate the phase composition.The microstructure and elements of a particular region were examined by using scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)respectively Meanwhile,nanoindentation and micro-hardness techniques were applied to test the mechanical properties of the Ti-6Al-4V/Ti B_wbulk.The results show that the main phase exists in the form ofα-Ti based on high laser power and fast scanning speed.Rapid cooling rate inhibites grain growth leading to generate a large number of fine grain structures.While a small quantity of unmelted Ti-6Al-4V powders lie on the matrix.The mechanical performance shows that the elastic modulus at 147 GPa and microhardness at 500-600 HV of the samples in this experiment have improved significantly compared with conventional cast TC4.
引文
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[2]戚运莲,曾立英,侯智敏,等.硼对TC4/B钛合金铸造组织与性能的影响[J].钛合金工业进展,2012,29(6):15-18.
[3]Li, Wei.Effect of substrate preheating on the texture, phase and nanohardness of a Ti-45Al-2Cr-5Nb alloy processed by selective laser melting[J].Scripta Materialia,2016,118:13-18.
[4]Rastegari H, Abbasi S M.Producing Ti-6Al-4V/TiC composite with superior properties by adding boron and thermo-mechanical processing[J].Materials Science&Engineering A,2013,564(3):473-477.
[5]Hung Y C, Bennett J A, Garcia-Pastor F A, et al.Fatigue crack growth and load redistribution in Ti/SiC composites observed in situ[J].Acta Materialia,2009,57(2):590-599.
[6]Hung Y C, Withers P J.Fibre bridging during high temperature fatigue crack growth in Ti/SiC composites[J].Acta Materialia,2012,60(3):958-971.
[7]代文豪,杨立军,党新安.钛合金粉末的选择性激光熔化表面质量研究[J].热加工工艺,2016,45(18):80-83.
[8]李佳桂,史玉升,鲁中良,等.选择性激光熔化成形瞬态温度场数值模拟[J].中国机械工程,2008,19(20):2492-2495.
[9]Almangour B, Grzesiak D, Yang J M.Selective laser melting of TiB2/316L stainless steel composites:the roles of powder preparation and hot isostatic pressing post-treatment[J].Powder Technology,2017(309):37-48.
[10]Soboyejo W O, Shen W, Srivatsan T S.An investigation of fatigue crack nucleation and growth in a Ti-6Al-4V/TiB in situ composite[J].Mechanics of Materials,36(1):141-159.