激光粉床熔融Ti-6Al-4V热处理的研究现状:微观组织演变和耐腐蚀性能

针对激光粉床熔融Ti-6Al-4V热处理问题,对现有文献进行总结,讨论热处理对激光粉床熔融Ti-6Al-4V的组织和腐蚀行为的影响.围绕组织决定材料性能这一观点,通过扫描电子显微镜观察热处理前后激光粉床熔融Ti-6Al-4V微观组织变化,恒电位极化实验分析耐腐蚀性能的差异,将热处理前后激光粉床熔融Ti-6Al-4V的组织和耐腐蚀性能变化相联系,两者相互比较印证.结果发现,细针状α′马氏体相和残余应力是造成激光粉床熔融Ti-6Al-4V耐腐蚀性能变差的主要原因,适当的热处理可以促进细针状α′马氏体分解,增加体心立方β相,消除残余应力,改善激光粉床熔融Ti-6Al-4V的耐蚀性能.同时,过分的热处理会造成激光粉床熔融Ti-6Al-4V晶粒度的增加,影响钝化膜的稳定性.最后,总结现有结论,对激光粉床熔融Ti-6Al-4V热处理未来发展做出展望.

扫描间隙对激光粉床熔融GH4169合金微观组织及硬度的影响

目的研究相同激光功率、扫描速度及粉层厚度条件下,激光粉床熔融GH4169合金微观组织、硬度及密度在不同扫描间隙条件下的演变规律。方法采用激光粉床熔融设备制备了GH4169合金试样,通过扫描电子显微镜对微观组织进行了观察,采用硬度仪测量了试样硬度,基于阿基米德原理测量了试样密度。结果随着扫描间隙的增加,激光粉床熔融GH4169合金的熔合不良缺陷增多,密度逐渐降低。结论扫描间隙对激光粉床熔融GH4169合金的微观组织、硬度及密度具有显著影响,合理选取扫描间隙参数,可有效减少熔合不良缺陷,提高致密度和硬度。

构建方向对激光粉床熔化NiTi记忆合金微观组织和功能特性的影响

在激光粉床熔化(LPBF)技术制造三维金属构件过程中,构建方向导致的热历史差异可能会引起晶粒形态、缺陷数量和相组成的变化,从而影响构件的力学性能和功能特性。探讨了0°、45°和90°3种构建方向对NiTi形状记忆合金微观组织和力学性能的影响。采用扫描电子显微镜(SEM)、光学显微镜、X射线衍射(XRD)和差示扫描量热法(DSC)分析了LPBF制备NiTi合金的微观组织和相变行为,并通过变温拉伸测试评估了NiTi合金在马氏体和奥氏体状态下的力学性能和功能特性。结果表明,0°、45°和90°样品的熔池类型分别为传导模式、混合模式和匙孔模式。在室温和100℃下,0°、45°和90°样品的拉伸应变分别为10.5%/8.5%、17%/11%和9.5%/5.5%。在室温下拉伸6%后,3组样品的可恢复应变分别为3.3%、3.4%和3.8%。

激光粉床增材制造不锈钢中氧化物夹杂调控的研究进展

激光粉床增材制造技术是一个涉及熔池移动、快速非平衡凝固、固态相变的复杂冶金过程,该过程的非均匀快速热-力耦合易导致金属制件出现翘曲变形、裂纹及孔洞、夹杂物、晶粒异常形核与长大等缺陷,这些缺陷会对金属制件的尺寸精度、致密度及力学性能等产生不利影响。激光粉床增材制造金属制件中非金属氧化物夹杂大多为内生夹杂物,产生于金属液脱氧以及极速熔化和凝固过程中的二次氧化,其种类、尺寸、形貌以及分布等物化特性直接影响或决定了金属产品的质量与性能,也是导致金属中产生各类缺陷的重要原因之一。分析了不锈钢材料激光粉床增材制造及后续热处理过程金属中氧化物夹杂的形成和演化及其对金属零件性能的影响性,并对不锈钢金属制件中氧化物夹杂特性的调控研究进展进行了总结,为激光粉床增材制造企业生产工艺优化提供了科学指导和理论依据。

多激光粉床熔融成形GH3536合金搭接区域组织与性能特征研究

利用多激光粉床熔融(ML-PBF)设备成形了GH3536高温合金,系统研究了单激光区、双激光区以及四激光区成形试样的缺陷、显微组织和拉伸性能的变化规律。结果表明:随着激光束的增多,试样表面质量得到改善,但致密度由99.82%(单激光区)降低到92.35%(双激光区)和98.97%(四激光区)。同时,多激光搭接区的重熔导致部分晶粒再结晶,沿(001)的择优生长取向更加显著,织构指数也由单激光成形试样的3.040分别提升到了3.403和3.465。但是,单激光区、双激光区和四激光区的大角度晶界比例逐渐降低,由65.9%分别降低到50.1%和46.3%。此外,搭接区的残余应力呈现降低趋势,单激光区、双激光区和四激光区分别为192.3 MPa,106.5 MPa和44.1 MPa。三者的室温拉伸强度相差较小,均达到了800 MPa以上,断裂延伸率由30.3%(单激光区)降低到25.9%(双激光区)和25.4%(四激光区),这主要是搭接区内的孔洞和裂纹缺陷造成的。研究结果有望为多激光粉床熔融制备大尺寸镍基高温合金零部件提供有效的参考。

激光粉床熔融铝合金熔池热动力学数值模拟

基于有限体积方法建立了激光粉床熔融(LPBF)介观尺度熔化凝固物理模型,考虑了温度函数的热物性参数和材料气化反冲压力模型,研究了激光扫描速度对LPBF成形AlSi10Mg合金非平衡熔池温度场、速度场、残余孔隙与表面品质的影响,揭示了粉末熔化温度场、熔体润湿铺展行为、熔体热毛细流动对表面自由面波动和致密化行为的作用机制,形成的熔池热动力学行为可为调控LPBF成形高致密和高品质表面形貌提供参考。

激光增材制造钛铝系金属间化合物的研究现状

随着我国工业技术的不断发展,发动机材料已经成为制约我国航空技术发展的壁垒。降低能源损耗,提高使用温度成为诸多发动机材料的发展方向。TiAl合金具有密度低、抗氧化性能好、比强度高等优点,是极具潜力的低压涡轮发动机备选材料。为探究激光增材制造技术所制备的TiAl合金在航空发动机上的应用前景,详细介绍了激光增材制造所需TiAl粉末和相关的激光增材制造技术,以及利用激光增材制造技术制造TiAl合金的研究现状。分析了使用激光增材制造技术制造TiAl合金的优势以及存在的缺点,提出了目前激光增材制造TiAl合金还需要深入研究的问题。

Effect of process parameters on microstructure and mechanical properties of a nickel-aluminum-bronze alloy fabricated by laser powder bed fusion

This work investigated the effect of process parameters on densification,microstructure,and mechanical properties of a nickel-aluminum-bronze(NAB)alloy fabricated by laser powder bed fusion(LPBF)additive manufacturing.The LPBF-printed NAB alloy samples with relative densities of over 98.5%were obtained under the volumetric energy density range of 200−250 J/mm^(3).The microstructure of the NAB alloy printed in both horizontal and vertical planes primarily consisted ofβ'martensitic phase and bandedαphase.In particular,a coarser-columnar grain structure and stronger crystallographic texture were achieved in the vertical plane,where the maximum texture intensity was 30.56 times greater than that of random textures at the(100)plane.Increasing the volumetric energy density resulted in a decrease in the columnar grain size,while increasing the amount ofαphase.Notably,β_(1)'martensitic structures with nanotwins and nanoscaleκ-phase precipitates were identified in the microstructure of LPBF-printed NAB samples with a volumetric energy density of 250 J/mm^(3).Furthermore,under optimal process parameters with a laser power of 350 W and scanning speed of 800 mm/s,significant improvements were observed in the microhardness(HV 386)and ultimate tensile strength(671 MPa),which was attributed to an increase in refined acicular martensite.

Effect of Ni on microstructure and mechanical properties of Al−Mg−Si alloy for laser powder bed fusion

The microstructures and mechanical properties were systematically studied for the high-strength Al−5Mg_(2)Si−1.5Ni alloy fabricated by laser powder bed fusion(L-PBF).It is found that the introduction of Ni(1.5 wt.%)into an Al−5Mg_(2)Si alloy can significantly improve the L-PBF processibility and provide remarkable improvement in mechanical properties.The solidification range of just 85.5 K and the typical Al−Al3Ni eutectics could be obtained in the Ni-modified Al−5Mg_(2)Si samples with a high relative density of 99.8%at the volumetric energy density of 107.4 J/mm^(3).Additionally,the refined hierarchical microstructure was mainly characterized by heterogeneousα-Al matrix grains(14.6μm)that contain the interaction between dislocations and Al−Al3Ni eutectics as well as Mg_(2)Si particles.Through synergetic effects of grain refinement,dislocation strengthening and precipitation strengthening induced by Ni addition,the L-PBFed Al−5Mg_(2)Si−1.5Ni alloy achieved superior mechanical properties,which included the yield strength of(425±15)MPa,the ultimate tensile strength of(541±11)MPa and the elongation of(6.2±0.2)%.

Effects of tantalum addition on microstructure and properties of titanium alloy fabricated by laser powder bed fusion

The expanding of material library of laser powder bed fusion(L-PBF)is of great significance to the development of material science.In this study,the biomedical Ti-13Nb-13Zr powder was mixed with the tantalum particles(2 wt%−8 wt%)and fabricated by L-PBF.The microstructure consists of aβmatrix with partially unmelted pure tantalum distributed along the boundaries of molten pool owing to the Marangoni convention.Because the melting process of Ta absorbs lots of energy,the size of molten pool becomes smaller with the increase of Ta content.The fine microstructure exists in the center of melt pool while coarse microstructure is on the boundaries of melt pool because of the existence of heat-affected zone.The columnar-to-equiaxed transitions(CETs)happen in the zones near the unmelted Ta,and the low lattice mismatch induced by solid Ta phase is responsible for this phenomenon.The recrystallization texture is strengthened while the fiber texture is weakened when the tantalum content is increased.Due to the formation of refined martensiteα′grains during L-PBF,the compressive strengths of L-PBF-processed samples are higher than those fabricated by traditional processing technologies.The present research will provide an important reference for biomedical alloy design via L-PBF process in the future.

LPBF成型加Ti铝基合金的组织特性及其对纳米硬度的影响

论述了在激光粉末床熔融(LPBF)成型Al基合金中添加Ti的影响。采用扫描电镜、电子背散射衍射、X射线衍射、透射电镜和纳米压痕测试等方法,研究了Ti含量为3%(质量分数,下同)和不含Ti的LPBF制备样品的显微组织特征、相分布和纳米硬度。结果表明,该方法可获得较细的晶粒组织和较小的平均晶粒尺寸。由于Al_(3)Ti析出相的非均相形核,晶粒尺寸范围减小到2.5μm以内。随着小角度晶界的增大,晶格畸变能增大,平均纳米硬度和杨氏模量分别提高到2.36和92.72 GPa。添加3%Ti后,LPBF处理的Al基合金<100>织构略有增强,但仍有一个随机的晶体取向。获得了α-Al向Al_(3)Ti的相变。

Influence of Post-Treatment Process on Microstructure and Properties of Laser Additively Manufactured Nickel-Based Superalloy

Defects such as cracks and micropores exist in nickel-based superalloy during laser powder bed fusion(LPBF),hindering their application in various fields.Hot isostatic pressing(HIP)was combined with conventional heat treatment(HT)to obtain LPBF nickel-based superalloy parts with ideal properties and fewer defects.The results show that HIP process can improve the densification,while the conventional HT can eliminate the micro-defects to improve the mechanical properties.After HIP treatment,the defect volume fraction of LPBF specimens decreases.After HT,the defect content of HIP+HT specimens increases slightly.After post-treatment,the hardness shows a decreasing trend,and the tensile strength and post-break elongation of HIP+HT specimens increase to 1326 MPa and 21.3%,respectively,at room temperature.