激光成形修复K418高温合金的显微组织与开裂行为

研究了激光成形修复航空发动机涡轮叶片用K418高温合金的组织特征与开裂行为。研究发现:K418合金激光修复区组织主要由γ-FeCr0.29Ni0.16C0.06固溶体基体、方形γ′相、枝晶间杆状或骨架状初生MC碳化物和骨架状(γ+MC)共晶组成。激光成形修复所用铸件基体中MC碳化物为TiC,呈块状分布在晶内和晶界;而激光修复区中MC碳化物为(NbTi)C,呈骨架状或杆状分布于枝晶间。从基体、热影响区到修复区,γ′相形貌、尺寸和数量呈现不同特征。修复区裂纹为与液膜有关的结晶裂纹,裂纹沿枝晶晶界扩展。通过试验优化,确定了较佳的激光成形修复K418合金的工艺参数,大大降低了其开裂倾向。     

Selective Laser Melting of Carbon-Free Mar-M509 Co-Based Superalloy: Microstructure,Micro-Cracks,and Mechanical Anisotropy

In this work,the microstructural evolution,micro-crack formation,and mechanical anisotropy of the selective laser melted(SLM) carbon-free Mar-M509 Co-based superalloy were systematically studied under different linear energy densities(LED).Observation shows that the SLM Mar-M509 superalloy possesses a fully dense structure,whereas some microcracks exist along the building direction.The electron backscatter diffraction results reveal that dominant columnar grains tend to elongate along the buildi...     

Influence of Selective Laser Melting Process Parameters on Microstructure and Properties of a Typical Ni-Based Superalloy

The influence of selective laser melting(SLM) process parameters on the microstructure and mechanical properties of a typical Ni-based superalloy was researched. The optimum parameters of P = 170 W, V = 0.8 m/s were determined, under which the SLMed samples exhibited both the largest relative density of 99.57% and the best mechanical properties, including the microhardness(329.3 ± 3.8 HV), yield strength(726 ± 8.1 MPa), ultimate tensile strength(900 ± 5.9 MPa) and elongation((31.9 ± 0.24)%). The...     

激光熔化沉积定向快速凝固高温合金组织及性能

采用激光熔化沉积定向快速凝固工艺,制备出了具有快速定向生长微细柱晶组织的Rene95高温合金板状试样,其一次枝晶间距约为7 μm、枝晶间完全无γ/γ'共晶组织析出.结果表明,激光熔化沉积定向快速凝固微细柱晶Rene95高温合金具有优异的力学性能.     

选区激光熔化Al-Mg-Sc-Zr合金成形性及力学性能研究

通过选区激光熔化(SLM)技术制备Al-Mg-Sc-Zr铝合金,系统研究了不同工艺参数对铝合金粉末成形性以及不同时效处理条件对SLM成形样品组织和力学性能的影响。结果表明,在高激光功率和低激光扫描速度下,SLM成形样品的致密度较高。沿样品沉积方向可观察到熔池层层堆叠的显微组织,熔池边界和熔池内部均存在细小纳米颗粒。经不同温度时效处理后,样品的硬度和压缩屈服强度先增加后降低。SLM成形样品经400℃时效处理3 h后屈服强度达到最大值469±4 MPa。     

激光选区熔化Cr3C2/CoCrMo合金的组织结构及力学性能研究

通过激光选区熔化(SLM)技术制备了高致密度的CoCrMo和Cr3C2/CoCrMo合金,对比研究CoCrMo和Cr3C2/CoCrMo合金的组织结构、拉伸性能及磨损性能,探讨添加Cr3C2颗粒对CoCrMo合金组织及性能的影响机制。研究发现,合金的主要组成相为γ-Co和ε-Co,添加Cr3C2使合金的物相发生改变,产生M23C6相。CoCrMo与Cr3C2/CoCrMo合金的组织均由外延生长的柱状晶和等轴晶组成,添加Cr3C2使柱状晶数量减少。Cr3C2/CoCrMo合金的硬度为514±18 HV,抗拉强度为1520 MPa,相比于CoCrMo合金分别提升了27%、39%。在相同载荷下,Cr3C2/CoCrMo合金的磨损量明显小于CoCrMo合金,耐磨性能提升30%。在SLM过程中,添加的Cr3C2颗粒快速熔解,Cr固溶在基体中,产生固溶强化;在晶界处转变生成M23C6型碳化物,具有沉淀强化作用,有效提高了合金的强度和耐磨性。     

高Mg含量Al-Mg-Sc-Zr合金选区激光熔化成形性及力学性能

基于宽粒径分布粉末(2～46 μm),应用选区激光熔化(SLM)技术制备了高Mg含量Al-14.4Mg-0.33Sc-0.19Zr铝合金.系统研究了不同工艺参数和时效处理条件对合金SLM 成形性、组织和力学性能的影响.结果表明,高激光功率可有效降低细粉飞溅对样品成形性的干扰,SLM 成形样品的最大相对密度为98.6％....     

激光工艺参数对选区激光熔化钽微观组织和力学性能的影响

研究了单、双层扫描策略和能量密度（246~640 J/mm³）对选区激光熔化钽显微组织及力学性能的影响。采用扫描电子显微镜和电子背散射衍射对选区激光熔化钽的显微组织进行表征,并对其显微硬度和拉伸性能进行检测。结果表明,选区激光熔化钽显微组织由明显向上生长的柱状晶构成,双层扫描后的钽具有更细的晶粒尺寸。随着输入能量密度的提高,选区激光熔化钽的强度、显微硬度和塑性均具有明显的上升趋势。此外,双层扫描工艺可进一步提高材料密度,且在保留强度的基础上,增强材料塑性。在能量密度为640 J/mm³（双层扫描）时,金属钽性能最优,显微硬度、极限抗拉伸强度及延伸率分别为2307 MPa,527 MPa和11.4%。     

造粒烧结WC颗粒对选区激光熔化18Ni300基复合材料微观组织及力学性能影响

为明确低成本WC颗粒增强钢基复合材料的组织演变过程和使用安全性,以造粒烧结球形WC颗粒为增强相,通过选区激光熔化制备了颗粒增强18Ni300钢基复合材料,研究了增强体体积分数对材料组织和冲击性能的影响。结果表明,WC颗粒加入量是影响材料致密度、成形质量和冲击韧性的主要因素,WC颗粒部分溶解导致基体中W、C含量增加,α-Fe相转变被抑制,晶粒尺寸发生改变。随着WC含量的增加,基体组织逐渐转变为γ-Fe相,晶粒尺寸增大。WC质量分数从0%增加到20%时,试样平均冲击值从为49.25 J下降为8.50 J,断口逐渐转变为脆性断裂形貌。     

Selective Laser Melting of 30CrMnSiA Steel: Laser Energy Density Dependence of Microstructural and Mechanical Properties

Three-dimensional parts of the 30 CrMnSiA steel were successfully fabricated using selective laser melting(SLM). The microstructures and mechanical properties of the SLM-processed 30 CrMnSiA samples were investigated by scanning electron microscope and transmission electron microscopy. The results indicate that the microstructures of the 30 CrMnSiA samples consist mainly of lath martensite and acicular martensite. The value of the surface roughness decreases with increasing laser energy density(LED) before it reaches a minimum and then increases with further increasing LED. The relative density, microhardness and ultimate tensile strength of the SLM-processed samples initially increase and then decrease with increasing LED. By taking the relative density, surface roughness, microhardness and ultimate tensile strength into account, the optimized LED should be in the range of 46.15–51.28 J mm~(-3) for the SLM-processed30 CrMnSiA alloys. In addition, the differences in the microstructures and mechanical properties between the conventionally wrought 30 CrMnSiA sample and SLM-processed 30 CrMnSiA samples were also studied.     

间接选择性激光烧结与选择性激光熔化对比研究

采用选择性激光烧结（Selective laser sintering，SLS）和选择性激光熔化（Selective laser melting，SLM）工艺，分别进行了铁基合金粉末的快速成形试验，对比分析了SLS与SLM成形机理、相应的工艺参数以及它们对测试件成形过程、金相组织与力学性能的影响。结果表明：由于成形机理不同，相对于SLS技术，采用SLM能够制造高致密度、组织均匀、力学性能良好的金属零件，但容易出现翘曲变形、裂纹与球化现象。通过制定合适的材料与工艺参数能够避免上述缺陷。     

激光选区熔化成形Kanthal涂层及其微波衰减特性研究

采用两种球形Kanthal合金粉末（颗粒直径45-60um和50-70um）,通过激光选区熔化(Selective laser melting, SLM)技术制备Kanthal涂层。利用光学显微镜、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和谐振腔特性测量系统对Kanthal粉末及涂层的表面形貌、显微组织、相结构和谐振腔品质因子进行检测分析。研究结果表明：SLM成形Kanthal涂层具有表面粗糙、多孔结构、扁平化的特点,与无氧铜基金属结合牢固,形成了冶金结合界面。其中45-60um球形合金粉末SLM成形涂层加载谐振腔品质因子(Quality factor)Q值整体比50-70um粉末成形涂层的Q值低,在频率2985MHz下微波衰减特性更强。涂层成形过程中形成的Al2O3膜和微孔洞使得合金涂层能够散射微波,减少了对微波的反射。涂层厚度对微波有干涉损耗,厚度0.55mm的Kanthal涂层加载谐振腔Q值最小,达到2280。Kanthal涂层是以磁衰减为主的复合衰减材料。     

Si-Assisted Solidification Path and Microstructure Control of 7075 Aluminum Alloy with Improved Mechanical Properties by Selective Laser Melting

The construction and application of traditional high-strength 7075 aluminum alloy (Al7075) through selective laser melting (SLM) are currently restricted by the serious hot cracking phenomenon. To address this critical issue, in this study, Si is employed to assist the SLM printing of high-strength Al7075. The laser energy density during SLM is optimized, and the effects of Si element on solidification path, relative density, microstructure and mechanical properties of Al7075 alloy are studied systematically. With the modified solidification path, laser energy density, and the dense microstructure with refined grain size and semi-continuous precipitates network at grain boundaries, which consists of fine Si, β-Mg₂Si, Q-phase and θ-Al₂Cu, the hot cracking phenomenon and mechanical properties are effectively improved. As a result, the tensile strength of the SLM-processed Si-modified Al7075 can reach 486 ± 3 MPa, with a high relative density of ~ 99.4%, a yield strength of 291 ± 8 MPa, fracture elongation of (6.4 ± 0.4)% and hardness of 162 ± 2 (HV_0.2) at the laser energy density of 112.5 J/mm³. The main strengthening mechanism with Si modification is demonstrated to be the synergetic enhancement of grain refinement, solution strengthening, load transfer, and dislocation strengthening. This work will inspire more new design of high-strength alloys through SLM.     

激光立体成形K465高温合金的组织研究

采用激光立体成形技术制备了K465镍基高温合金试样,研究了晶粒、γ′强化相及碳化物等组织的特征及演化规律。结果表明:试样中心区域内晶粒粗大,顶部边缘区域晶粒细小;试样内枝晶呈现明显的沿沉积方向外延生长特点,在接近试样底部的部分,熔覆层顶部由于重熔不完全而出现转向枝晶区;熔覆层交界处的γ′相尺寸略大于层内的γ′相,枝晶间的γ′相尺寸略大于枝晶干上的γ′相;MC碳化物呈现多种形貌,底部存在分叉发达的花瓣状MC碳化物,中部有较多短棒状MC碳化物,顶部存在棒状和八面体状的MC碳化物。     

Selective Laser Melting of Al-7Si-0.5 Mg-0.5Cu: Effect of Heat Treatment on Microstructure Evolution,Mechanical Properties and Wear Resistance

Al-7Si-0.5 Mg-0.5Cu alloy specimens have been fabricated by selective laser melting (SLM). In this study, the effects of solution treatment, quenching, and artificial aging on the microstructural evolution, as well as mechanical and wear properties, have been investigated. The as-prepared samples show a heterogeneous cellular microstructure with two different cell sizes composed of α-Al and Si phases. After solution-treated and quenched (SQ) heat treatment, the cellular microstructure disappears, and coarse and lumpy Si phase precipitates and a rectangular Cu-rich phase were observed. Subsequent aging after solution-treated and quenched (SQA) heat treatment causes the formation of nanosized Cu-rich precipitates. The as-prepared SLMs sample has good mechanical properties and wear resistance (compressive yield strength: 215 ± 6 MPa and wear rate 2 × 10^-13 m³/m). The SQ samples with lumpy Si particles have the lowest strength of 167 ± 13 MPa and the highest wear rate of 6.18 × 10^-13 m³/m. The formation of nanosized Cu-rich precipitates in the SQA samples leads to the highest compressive yield strength of 233 ± 6 MPa and a good wear rate of 5.06 × 10^-13 m³/m.     

选区激光熔化成形工艺对2024铝合金组织性能的影响

采用选区激光熔化(Selective Laser Melting,SLM)技术成形了2024铝合金,研究了扫描间隔对显微组织及室温力学性能的影响。结果表明:扫描间隔0.12 mm时,2024铝合金显微组织细小,硬度达124 HB,抗拉强度为372 MPa,具有较高的室温力学性能。     

浇注温度对K417G合金组织及力学性能的影响

研究了不同浇注温度下的K417G合金试样。结果表明,1 450℃浇注,合金中碳化物以块状为主,γ′相边缘钝化,γ′尺寸为1μm左右;1 500℃浇注,合金中碳化物以长条形为主,γ′相边缘清晰,立方度较好,γ′尺寸为0.8μm左右。1 450℃浇注的合金屈服强度及断裂强度均高于1 500℃浇注的合金。合金拉伸裂纹主要产生于碳化物处,1 450℃浇注的合金,碳化物尺寸较小,产生裂纹需要的应力较大;1 500℃浇注的合金,碳化物细长,碳化物断裂所需应力较小。在760℃/645 MPa条件下,1 450℃浇注的合金,平均持久寿命可达到219 h,而1 500℃浇注的合金,平均持久寿命仅为25 h。前者的断裂方式为穿晶断裂,后者为沿枝晶断裂,断口上存在有部分疏松组织。     

选区激光熔化成形TiN/Inconel 718复合材料的组织和力学性能

采用选区激光熔化(selective laser melting,SLM)工艺制备了TiN/Inconel 718(IN718)复合材料,利用OM、SEM、EDS、EBSD以及XRD等手段研究了SLM成形态和不同热处理条件下TiN/IN718复合材料的微观组织和力学性能.结果表明:SLM成形态TiN/IN718复合材料中TiN颗粒与基体之间紧密结合,并形成了约为0.3μm厚的过渡层,与IN718合金相比,TiN/IN718复合材料的显微硬度和拉伸强度均有明显改善(分别提高39 HV0.2和74 MPa).双时效(DA)和固溶时效(SA)热处理的TiN/IN718复合材料中,强化相的析出和TiN颗粒的存在导致裂纹萌生源增多,从而造成强度没有得到明显提升.均匀化+固溶时效(HSA)热处理后材料发生了完全再结晶,晶粒内部析出了超细球状的γ'/γ'强化相,晶界处和晶粒内部TiN颗粒周围的针状δ相含量增加.因此,经过HSA处理后材料的抗拉强度有显著提升,达到1430 MPa(提高了410 MPa).     

热处理对激光选区熔化TC4钛合金显微组织和力学性能的影响

研究了激光选区熔化(SLM) TC4钛合金沉积态和退火态显微组织的特征及其对力学性能的影响规律。结果表明:合金组织沿激光选区熔化成形高度方向呈现外延生长,形成柱状晶,晶内存在大量的针状马氏体α''相。退火后,晶内的针状α''相转变为α+β板条组织。随着退火温度的升高,组织中α相含量逐渐降低,α片层逐渐粗化,β相含量逐渐升高;室温拉伸强度逐渐降低,塑性逐渐升高,显微硬度逐渐降低。经过800℃×2 h/FC退火热处理后,激光选区熔化成形TC4钛合金具有最佳的强度与塑性匹配。     

选区激光熔化成形AlSiMg3合金

基于选区激光熔化（SLM）技术熔体快速冷却的特点,通过提高Al-Si-Mg合金中Mg的含量,设计获得SLM技术专用AlSiMg3合金。系统研究了不同工艺参数和时效处理条件对SLM成形AlSiMg3合金组织和硬度的影响。结果表明,SLM成形样品均由α-Al、Si和Mg2Si相构成。高激光能量密度有利于增加粉末样品的成形性,当激光功率为160 W,扫描速度为200 mm/s时,样品具有最低孔隙率0.07%。随着激光扫描速度的增加,样品中富Si组织的比例逐渐升高,Mg元素在α-Al中固溶量逐渐增大,使得SLM成形样品的硬度逐渐升高,最大值为194±3 HV。样品经150 ℃时效处理后,由于α-Al内部纳米颗粒的析出,导致样品硬度增大,最大值为210±2 HV,远高于现有报道的SLM成形Al-Si和Al-Si-Mg铝合金。本研究报道了成形性和力学性能优异的SLM专用Al-Si-Mg合金。