18Ni300模具钢激光选区熔化工艺优化及力学性能研究

优化激光选区熔化工艺, 制备18Ni300模具钢试样, 研究扫描速度和激光功率对模具钢力学性能的影响。结果表明, 当激光功率保持不变时, 随着扫描速度的增加, 18Ni300模具钢试样的相对密度和综合力学性能先增大后减小; 当扫描速度保持不变时, 随着激光功率的增加, 试样相对密度和综合力学性能逐渐增大; 能量密度在150 J·mm-3左右时, 试样的相对密度达到最高。激光选区熔化最优工艺参数是激光功率175W, 扫描速度400mm·s-1, 在此工艺参数下成形件的相对密度为99.58%, 抗拉强度、显微硬度和断后伸长率分别为1101 MPa、HV 348.4和6.44%。     

激光选区熔化纯钨防散射栅格的工艺及性能研究

为探究激光选区熔化(SLM)成形纯钨防散射栅格的最佳工艺参数，研究了不同工艺参数对于栅格试样的表面粗糙度、熔道厚度、压缩力学性能以及钨实体试样致密度、微观组织的影响规律。研究发现，栅格试样的表面粗糙度会随着激光功率和扫描速度的增加而增加，过高的激光功率容易产生球化现象。此外，激光功率的增加以及扫描速度的减小都会使得熔道的厚度尺寸增加，在200 W激光功率以及500 mm·s^-1扫描速度工艺条件下熔道厚度最为接近100μm的预设值。压缩测试结果表明，纯钨薄壁栅格件的抗压强度会随着激光功率的增加以及扫描速度的减小而增加，且试样最大抗压强度达到了172 MPa。实体试样的致密度会随着激光扫描速度增加而减小，并且随着激光功率的增加先增大再减小，最终在375 W激光功率以及500 mm·s^-1扫描速度工艺条件下获得98.36%的最大致密度。其构建方向组织多为柱状晶粒，并且晶粒会随着激光功率的减小以及扫描速度的增加而细化。最后根据探究的工艺参数对栅格熔道形貌及厚度尺寸的影响规律，通过工艺优化，在210 W-600 mm·s^-1以及3...     

选区激光熔化工艺参数对气雾化316L不锈钢粉末成形制品性能的影响

本研究系统考察了激光功率和扫描速度对316L不锈钢粉末选区激光熔化工艺成形熔道、制品微观组织及力学性能的影响,并分析了各类缺陷的形成原因。研究结果表明:在低激光功率和高扫描速度条件下,熔道中出现了大量球状颗粒,这些颗粒之间的空隙恶化了下一层粉末的熔化条件,这正是成形制品中熔道分布混乱以及孔洞、裂纹产生的根本原因,进而导致成形制品力学性能降低;在高激光功率和低扫描速度条件下,熔池快速升温/冷却的热应力作用增强,使得成形制品的熔道交界处也存在孔洞和裂纹等缺陷。在本研究实验条件下,激光功率为350 W,扫描速度为1750 mm/s时,SLM成形制品的力学性能最为优异,其中抗拉强度为731 MPa、屈服强度为638 MPa、断后伸长率为40.0%,致密度为96.27%。     

选区激光熔化成形GH4169合金研究现状

介绍了选区激光熔化成形GH4169合金存在的球化、孔洞等常见缺陷的形成机理及工艺控制现状，重点分析了激光功率、扫描速率、铺粉厚度等工艺参数对选区激光熔化成形GH4169合金成形件组织性能的影响规律，以及热处理、颗粒增强等组织性能调控手段对选区激光熔化成形GH4169合金组织性能影响。从工艺控制、材料强化设计等方面对选区激光熔化成形GH4169合金进行展望，认为利用选区激光熔化成形技术开展颗粒增强GH4169复合材料的设计与成形是进一步提升选区激光熔化成形GH4169合金性能的有效途径。     

选择性激光熔化镍基高温合金的工艺优化

采用实验设计田口法及响应面法,对镍基高温合金选择性激光熔化过程中的三个工艺参数（激光功率、扫描速度和扫描间距）进行优化,以成形样品的相对密度作为评价标准,研究工艺参数对最终试样相对密度的影响。基于方差分析、信噪比、主效应图、响应曲线图等,分析各因素及其之间的相互作用对样品相对密度的影响。研究结果表明,不同工艺参数对试样相对密度的影响效果差别很大,其中扫描间距的影响效果最大,其次是激光功率和扫描速度,此外扫描速度与扫描间距的交互作用对于试样相对密度的影响也比较显著。两种不同优化方法获得的最佳工艺参数组合相同,均为激光功率280 W、扫描速度1000 mm·s?1以及扫描间距0.12 mm。     

选择性激光熔化成形CoCrWMo合金工艺优化及摩擦磨损性能

对选择性激光熔化成形CoCrWMo合金的工艺参数进行优化,并对最佳工艺下合金试样的摩擦磨损性能进行分析。结果表明:选择性激光熔化最佳工艺参数为激光功率280 W,扫描速度800 mm?s?1,铺粉层厚0.03 mm,扫描间距0.10 mm,扫描策略为旋转扫描法（层与层之间旋转15°）。该工艺下激光体能量密度为117 J?mm?3,试样相对密度为99.4%,上表面粗糙度（Ra）为4.98 μm,显微硬度为HV 386,抗拉强度为984 MPa,屈服强度为663 MPa,断后伸长率为12.9%。在干摩擦下,CoCrWMo合金的平均摩擦系数随施加载荷的增加呈下降趋势;受磨损过程中应变诱导马氏体转变的影响,合金平均磨损率呈现先增高后降低的变化规律,主要磨损机制为磨粒磨损和粘着磨损。     

激光能量密度对选区激光熔化(SLM)制品性能的影响及其机理研究

选区激光熔化(SLM)影响制品性能的工艺参数包括激光功率、扫描速度等,上述因素可统一为激光能量密度(Laser Energy Density,LED)表示,激光能量密度的大小直接决定粉末的熔化状态,并最终影响SLM制品的性能。本文采用真空气雾化制备的GH4169粉末作为原料,设计了激光能量密度不同的对比实验,探讨了激光能量密度对于SLM制品的影响;建立了激光能量输入熔化粉末的计算关系,通过理论计算进一步研究了激光能量密度变化对制品产生影响的机理。研究结果表明:激光能量密度对于SLM成形制品存在影响,对于同种粉末,在一定参数范围内,激光能量密度越大的制品,其密度及硬度相对更高,而对于参数不同,激光能量密度相近的制品,粉末的熔化效果接近,密度及硬度水平相当;SLM工艺的主要影响因素为激光功率,扫描速度及粉末粒度,且激光功率对粉末熔化的影响相对较大,故对于相同成分及粒度粉末的SLM工艺参数优化而言,应当优先确定合适的激光功率,再调整扫描速度。     

选区激光熔化成形工艺参数对Fe20Cr5Al合金致密度和力学性能的影响

采用选区激光熔化(selective laser melting, SLM)成形技术进行3D打印,制备用于汽车尾气净化器载体的Fe20Cr5Al合金材料,采用响应曲面实验设计,系统研究打印参数(激光功率、扫描速度和扫描间距)与打印件致密度的关系,获得SLM成形参数与致密度的关系模型以及成形参数与力学性能的关系模型,并获得最佳的SLM成形工艺参数。结果表明,SLM工艺参数对打印件致密度的影响程度按从大到小依次为激光功率、扫描速度、扫描间距;最佳的SLM成形工艺参数为:激光功率314.8 W、扫描速度1 700 mm/s、扫描间距0.06 mm,在此工艺参数下相对密度的预测值为99.74%,这与SLM成形实验结果的平均误差仅为0.16%,模型具有较高的可靠性,在优化工艺参数下的平均实际相对密度达到99.58%,抗拉强度为616.44 MPa,伸长率为1.513%。     

激光选区熔化GH3536镍基高温合金组织与性能研究

研究了激光选区熔化（SLM）GH3536合金扫描面与建造面的组织与性能。采用光学显微镜（OM）、 X射线衍射仪（XRD）、扫描电镜（SEM）和电子背散射衍射（EBSD）对激光选区熔化GH3536合金金相、物相、微观组织和晶粒特征进行研究。结果表明，通过优化成形参数可以减少合金中孔隙与微裂纹，但是无法消除。半椭圆形熔池广泛分布于建造面，其宽深比约为1.5。激光选区熔化GH3536合金由单一的面心立方γ奥氏体组成。扫描面与建造面都分布着大量胞状与柱状亚晶，建造面熔池交界处存在沿建造方向的微裂纹。建造面的平均晶粒尺寸（145.1μm）约为扫描面晶粒尺寸的4.5倍，织构强度约为扫描面的2倍。横向与纵向试样的拉伸性能存在明显差异，横向试样的屈服强度和极限抗拉强度分别为645 MPa和781 MPa，分别比纵向试样高4.1%和7.0%。激光选区熔化GH3536合金断口呈明显韧性断裂，存在大量韧窝。本研究有望为激光选区熔化GH3536合金扫描面与建造面组织与性能差异提供有效的参考。     

激光参数和扫描策略对选择性激光熔化TC11合金成形性能的影响

采用选择性激光熔化技术制备了TC11合金试样,研究了激光参数和扫描策略对TC11合金成形性能的影响。结果表明:随着激光扫描速度的增加,合金表面黏附的金属球形颗粒增加,单道熔池宽度减小,试样表面变得粗糙。当激光扫描速度为0.6 m/s时,合金内部存在的孔隙为球形气孔;激光扫描速度大于1.2 m/s时,合金内部存在未熔不规则孔隙。随着激光功率的增加,单道熔池宽度增大,合金表面变得光滑;当激光功率不大于280 W时,样品内部存在极少量不规则未熔孔隙;激光功率为320 W时,样品内部存在极少量球形气孔。打印时采用每一层相对上一层旋转67°的扫描策略可以弥补上一层扫描时所造成的中心和边缘的高度差,避免高度差加大产生内部孔隙。为选择性激光熔化制备TC11合金选择合适的激光工艺参数和扫描策略提供了一定的参考依据。     

Mechanical properties of alloy Ti–6Al–4V and of stainless steel 316L processed by selective laser melting: influence of out-of-equilibrium microstructures

Abstract

Ti–6Al–4V and stainless steel 316L have been processed by selective laser melting under similar conditions, and their microstructures and mechanical behaviours have been compared in details. Under the investigated conditions, Ti–6Al–4V exhibits a more complex behaviour than stainless steel 316L with respect to the occurrence of microstructural and mechanical anisotropy. Moreover, Ti–6Al–4V appears more sensitive to the build-up of internal stresses when compared with stainless steel 316L, whereas stainless steel 316L appears more prone to the formation of ‘lack of melting’ defects. This correlates nicely with the difference in thermal conductivity between the two materials. Thermal conductivity was shown to increase strongly with increasing temperature and the thermophysical properties appeared to be influenced by variations in the initial metallurgical state.     

Metallurgical and mechanical characterisation of titanium based materials for endosseous applications obtained by selective laser melting

Abstract

The aim of the present work was to estimate the feasibility of selective laser melting (SLM) to produce Ti-hydroxyapatite bioactive composite materials for personalised endosseous implants. Mixtures of Ti6Al7Nb surface conditioned powder with hydroxyapatite up to 5 vol.-% were processed by SLM with the same scanning strategy and laser power in the range of 50–200 W. Specimens with porous structures were characterised from a structural and mechanical point of view. Irrespective to the initial hydroxyapatite content, density increased by increasing the laser power. The microstructure of manufactured parts mainly consisted of α′ martensite. In materials with 5 vol.-% hydroxyapatite, a phosphorous containing phase formed as a consequence of hydroxyapatite decomposition and interaction with the base Ti alloy. By increasing the laser power, the tensile strength increased mainly due to the density improvement of all the investigated materials.     

电镀Cr涂层对TC4钛合金燃烧性能的影响

通过对镀有不同厚度（0、15、30、60 μm）Cr涂层的TC4钛合金在不同氧压下进行的富氧点燃试验,研究了镀Cr层厚度对TC4钛合金燃烧性能的影响规律,并通过扫描电子显微镜（Scanning electron microscope, SEM）、能谱分析（Energy dispersive spectrometer,EDS）和X射线衍射（X-ray diffraction, XRD）等手段进行显微组织分析。结果表明:当Cr层厚度为15 μm和30 μm时,对TC4的燃烧临界氧压无明显影响,而Cr层厚度增加到60 μm时,可将TC4的燃烧临界氧压由0.07 MPa提高至0.15 MPa。同时,燃烧速率随Cr层厚度的增加而降低,说明Cr层厚度的增加能有效抑制火焰传播速度。其作用机理可能是在燃烧的过程中,表层Cr元素通过固相扩散、熔化等方式进入熔池,与合金中的Al、V元素共同析出,形成了弥散分布的富Cr、Al、V相,并减少了Al与O的结合,对O元素的扩散有阻碍作用,从而降低了燃烧速率。      

Influence of heat treatment conditions on the mechanical properties of Ti–6Al–4V alloy

In the current work, several heat treatments were carried out below and above the beta-transition temperature of the Ti–6Al–4V alloy followed by aging at 550 °C for 6 hours. The resultant microstructures and their effects on the mechanical properties of Ti–6Al–4V alloy were investigated. The results showed that solution treatment of Ti–6Al–4V samples followed by water quenching from β and α/β fields raised the alloy hardness from 380 to 575 and 656?HV, respectively, while no remarkable changes were observed after aging. The hot tensile strength of the as-forged sample increased from 671 to 756?MPa after water quenching from the ß- or α/ß- field, while the air cooling from β-phase field decreased the tensile strength to 644 MPa. The fracture mode of the tensile samples was more ductile in case of the solution-treated samples compared to the as-forged samples. A subsurface layer was formed due to the diffusion of oxygen into the surface at high temperatures. This layer which is known as ‘oxygen diffusion layer’ masked the differences of wear behaviour of the specimens.     

倾斜角度对激光选区熔化成形Ti6Al4V合金的影响

利用自主研发的Di Metal-100型激光选区熔化设备制备与基板平面成不同倾斜角的Ti6Al4V非标准拉伸试样,研究熔化成形后合金的显微组织、物理和力学性能。结果表明,Ti6Al4V合金粉末熔化成形后的组织为针状α′马氏体和(α+β)相,随倾斜角度变化,试样中α/α′相与β相的相对含量也发生变化,倾斜角为45°试样中β相含量最高;α′马氏体呈柱状分布于(α+β)相中,并且方向始终平行于成形方向(Z轴方向)。随SLM成形试样的倾斜角从0°增加到90°,其相对密度先减小后增大,并在90°时达到最大值96.1%;试样的硬度和抗拉强度均先升高后降低,在45°时达到最大值,硬度为393 HV,抗拉强度为1 288 MPa;试样表面粗糙度Ra也呈先增大后减小的趋势,在0°时达到最小值8.77μm,在30°时达到最大值19.55μm。     

Electron Beam Melting of High Niobium Containing TiAl Alloy: Feasibility Investigation

Third generation γ‐TiAl alloys with a high niobium content, Ti–(47–48)Al–2Cr–8Nb, were processed by electron beam melting (EBM). This near‐net‐shape additive manufacturing process produces complex parts according to a CAD design. The starting powder is deposited layer by layer on the building table and selectively melted to progressively form the massive part. The EBM parameters such as layer thickness, melting temperature, scanning speed, or building strategy were set up to minimize porosity. The chemical composition of the built material is similar to the composition of the base powder despite a slight evaporation of aluminum and reveals a neglectable oxygen pick‐up. The very fine equiaxed microstructure resulting after EBM can be then set up by heat treatment (HT). According to the HT temperature in particular, an equiaxed microstructure, a duplex microstructure with different lamellar ratio and a fully lamellar microstructure is obtained. Not only test bars have been produced but also complex parts such as demo low pressure turbine blades.     

Effect of microstructure on the tensile strength of Ti6Al4V specimens manufactured using additive manufacturing electron beam process

Electron beam melting additive manufacturing (AM) process has been developed for the manufacture of Ti6Al4V parts for the aerospace industry. In the AM research team from Airbus Group, this technology is being evaluated with a view to production of flight hardware. During the evaluation of the process, the microstructure variation as a function of geometry was studied. A distinctive microstructure was observed up to 0.5?mm from of part surface (the skin layer) and the thickness of the α-plate spacing varied depending on the thickness of the parts being produced. With the purpose of quantifying the influence of the grain thickness and the mechanical performance of the material, cylinders with nine different diameters (6 up to 40?mm diameter) were manufactured with 80?mm height. The microstructure characterisation showed how the α-plate spacing changed from thin to thick structures and the influence of grain size on tensile strength was quantified.