选择性激光熔化快速成型工艺研究

利用IPG200W光纤激光器和自主研发的SLM(Selective Laser Melting)快速成型设备,采用不同工艺参数组合,在25mm厚Q235钢板上进行不锈钢粉末单道熔覆实验。研究了激光功率、扫描速度对单道熔覆形貌和宽度、高度的影响规律;分析了选择性激光熔化球化现象产生机理及避免产生球化的途径;论述了最佳工艺参数的获取方法。结果表明:能量密度越高,熔覆形貌越好,球化现象越不明显;激光功率增大,单道熔覆宽度和高度也增加;扫描速度增大,单道熔覆高度和宽度减小。最后给出了几组最佳加工工艺参数和加工实例。     

选择性激光烧结技术在医学上的应用

简述了选择性激光烧结技术(SLS)和熔化技术(SLM)的成型原理及其在生物医学领域的应用,重点介绍了SLS在医学模型、植入体和赝复体、组织工程支架及药物传送装置等方面的应用,并对SLS和SLM技术的研究与发展方向进行展望。     

塑料粉末选择性激光烧结成型精度实验研究

采用正交方差分析法,对塑料粉末进行了烧结成型实验,实验发现,激光功率对烧结件密度的影响最大;而在对尺寸精度的影响上:对于X、Y平面方向,铺粉层厚的影响最大,在Z方向上,预热温度影响最大.通过对工艺参数影响规律的综合考虑,得到了激光烧结最佳工艺参数组合为,铺粉厚度0.15 mm,扫描速度1 600 mm/s,预热温度75 ℃,激光功率12 W.     

选择性激光烧结快速成形制件翘曲变形的研究

翘曲变形对选择性激光烧结(SLS)成形精度的影响很大.通过在HRPS-ⅢA型成型机上进行快速成型试验,找出产生翘曲变形的根本原因;得到了激光扫描速度和激光功率、粉末预热温度等工艺参数对翘曲变形的影响规律;并提出了减小翘曲变形的有效措施.     

选择性激光熔化制备纯钨的性能研究

以粒度集中的纯钨粉末为原料,通过选择性激光熔化技术(selective laser melting, SLM)制备样品,分别经过1000, 1400及1960℃的热处理2 h。研究不同相对密度和不同热处理后样品的力学性能和显微组织,并采用X射线衍射(XRD)表征其微观结构。结果表明:纯钨样品的相对密度处于75%～95%之间,其抗弯强度和显微硬度随相对密度的增加而增大,显微组织大体相似。经不同高温处理后,在1400℃处理后样品达到了最佳的力学性能,1960℃处理后样品的晶粒发生了明显的长大现象,材料力学性能降低。XRD图谱结果表明,SLM制得样品及经过1960℃烧结后,其晶体结构并未发生改变。     

选择性激光烧结铸造覆膜砂的实验研究

通过对铸造用覆膜砂烧结实验,激光功率、扫描速度、预热温度、光斑直径工艺参数对烧结试样成型精度和烧结质量的影响,总结出了制件尺寸随各工艺参数变化的趋势。并提出烧结制件后处理的合理温度范围。     

选择性激光烧结硅砂的实验研究

对间接选择性激光烧结硅砂进行了实验研究，通过对烧结后硅砂显微组织的观察，得出了硅砂烧结的机理。分析了激光功率、扫描速度、搭接量、光斑直径、粉末成分配比等工艺参数对烧结试样尺寸精度和烧结质量的影响，并得出了优化的工艺参数。烧结成形了一些砂模，经后处理后可用于铸造生产。     

不锈钢粉末的选择性激光熔化快速成形工艺研究

为了揭示选择性激光熔化快速成形过程中工艺对成形金属零件的影响规律,以不锈钢粉末为对象展开研究。首先,进行了单道扫描实验,结果表明水雾化制备的不锈钢粉末的单道扫描线不连续,球化现象严重,分析了其原因;然后,采用不同的成形工艺,成形出了金属块体,结果表明成形件的致密度与激光能量密度满足指数关系ρ=ρm-Aexp(-Ψ/K);最后,对选择性激光熔化成形件内部的显微组织进行了扫描电镜与光学显微分析,结果表明该组织极细小且不均匀,具有柱状和蜂窝状结构,熔化界面处的温度梯度最大,其组织变化最为剧烈。     

铸造硅砂选择性激光烧结工艺参数研究

对铸造硅砂的选择性激光烧结进行了试验研究。采用三维数字显微镜观察了烧结试样的微观形貌。系统研究了激光功率、扫描速度、搭接量、光斑直径、粉末配比等工艺参数对烧结试样尺寸精度和烧结质量的影响,分析了烧结质量的影响因素及提高质量的对策。获得了选择性激光烧结砂型试样。     

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.     

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...     

热处理对选区激光熔化GH3536合金晶界与拉伸行为的影响

采用选区激光熔化制备了GH3536合金,并分别进行固溶处理和热等静压处理,研究不同热处理手段对GH3536合金的组织形貌、晶界形态及室温拉伸行为的影响。结果表明:沉积态试样的组织由超细柱状亚晶粒与熔池界组成,存在气孔与微裂纹等缺陷;选区激光熔化试样分别经固溶处理和热等静压处理后,二者致密度均上升,组织转变为由交替分布的大小不等等轴晶粒组成,但热等静压的沿晶界析出M_(23)C_6相,形成锯齿状的弯曲晶界;沉积态试样的拉伸性能表现出各向异性的特点,固溶处理可消除拉伸性能的各向异性,但抗拉强度和屈服强度均有下降,延伸率明显上升。热等静压态试样与固溶态试样相类似,但其抗拉强度、屈服强度和延伸率均有进一步的提高;3种形态合金的断裂机制均为微孔聚集型的韧性断裂。     

Role of Co Content on Densification and Microstructure of WC–Co Cemented Carbides Prepared by Selective Laser Melting

WC–Co cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting(SLM) yet. The microstructure evolution as well as WC grain growth behavior has rarely been investigated in detail during SLM process. In this study, the WC–Co cemented carbides with different Co contents(12–32 wt%) were prepared by optimized SLM processes for comparative investigation of densification behavior, microstructure characterization and mechanical property. The increase in Co content in feedstock carbide granules can improve the densification behavior during SLM process. The SLM processed WC-12 Co shows larger average WC grain size and higher percentage of coarser WC grains as compared with both WC-20 Co and WC-32 Co. The microstructure characterization, combined with finite element simulation, shows the WC grain growth mechanisms include agglomeration and dissolution-deposition of WC during SLM process and agglomeration of WC is an important mechanism especially for WC–Co cemented carbides with Co content as low as 12 wt%. The comparison between horizontal(perpendicular to the SLM laser beam) and vertical(parallel to the SLM laser beam) cross sections of carbides shows that SLM process introduces a certain degree of microstructure and mechanical behavior anisotropy for WC-12 Co, WC-20 Co, and WC-32 Co.     

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。     

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。     

高效选择性激光烧结系统的研究

选择性激光烧结(Selective Laser Sintering,SLS)是快速成形技术的一种,其成形效率是需要考虑的重要指标之一。为了提高成形效率,我们从机械和工艺两方面着手研究和改进,并在华中科技大学研制的HRPS-III型SLS快速成形系统中应用,取得了良好的效果。     

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.