激光功率与扫描速度对选区激光熔化钴铬合金组织性能的影响

目的 明确选区激光熔化钴铬合金中激光线能量密度、激光功率和激光扫描速度对成形件组织、性能的影响,探究优化工艺参数的方法。方法 基于ANSYS有限元软件模拟选区激光熔化过程中熔池尺寸的基础上,通过金相显微镜分析了熔池尺寸和显微组织,电子背散射衍射分析了晶粒尺寸,使用力学试验机和洛氏硬度计研究了试样的力学性能。结果 随着线能量密度降低,成形件的熔池尺寸、晶粒大小、冷却速度和力学性能降低。但在激光线线能量密度为0.242 J/mm的条件下,扫描速度为1 200 mm/s时成形试样的致密度为98.7%,抗拉强度为867 MPa,延伸率为6.5%,其力学性能均高于扫描速度为950 mm/s时成形的试样,与线能量密度更高的0.263 J/mm成形条件下250 W+950 mm/s的成形试样力学性能相近。结论 激光线能量密度是影响选区激光熔化钴铬合金熔池尺寸和组织性能的关键因素,但熔池尺寸与激光线能量密度没有线性关系。相同的线能量密度下,增加激光扫描速度,有利于获得大的熔池尺寸和冷却速度,提高成形件的致密度和降低晶粒尺寸,最终使成形件力学性能提高。     

激光选区熔化WC 12Co复合材料温度场模拟研究北大核心CSCD

为提高激光选区熔化WC 12Co硬质复合材料的成形质量,采用有限元仿真软件Ansys 2021R1对SLM成形WC 12Co硬质复合材料过程的温度场进行数值模拟仿真研究,研究成形温度场的温度分布和成形工艺参数(激光功率、扫描速度、扫描间距和基板预热温度)对温度场的影响,为优化WC 12Co硬质复合材料成形提供试验依据。结果表明:激光功率增大,成形区域温度增大,位置点3的峰值温度从3507.47℃增大至3837.52℃;激光扫描速度增大,成形区域温度降低,位置点5的峰值温度从3592℃下降至2897℃,峰值温度下降695℃;扫描间距的增加使各扫描区域的温度有所降低,位置点3的峰值温度从3330℃逐渐降低至3123℃。在同一成形工艺参数下,激光扫描前一路径对后一路径有预热作用,随着扫描路径的增加,成形区域的温度呈现逐渐上升趋势。基板预热至120℃能够提高熔池的内部温度,减小成形件之间的温度差异,缩小温度梯度差。当激光功率增大时,熔池的宽度和深度随之增大;当激光扫描速度增大时,熔池的宽度先增大后减小,熔池的深度线性反向减小;当扫描间距增大时,熔池的宽度和深度均减小。模拟获得的温度场仿真结论能够大致反映成形试样的表面质量和合金粉末的熔化状态随成形工艺参数变化的趋势。     

工艺参数对激光选区熔化成形18Ni300钢冲击韧性的影响北大核心CSCD

为了解工艺参数对激光选区熔化成形材料抗冲击能力的影响规律及机制,利用金属摆锤试验机,对不同激光功率及扫描速度下,激光选区熔化成形18Ni300马氏体时效钢进行冲击韧性试验,采用金相显微镜及扫描电镜进行微观组织及断口形貌观察。试验结果显示:随着激光体能量密度的增加,激光选区熔化成形18Ni300钢内部孔洞形缺陷减少,融道内胞状晶数量减少,柱状晶数量增加,韧性冲击断口形貌逐渐由舌状滑移区和大而浅的韧窝转变为均匀小韧窝,最终导致18Ni300钢的冲击韧性增加。通过非线性拟合建立了激光选区熔化成形工艺参数及激光体能量密度与冲击韧性之间的关系。研究表明:激光功率、扫描速度对激光选区熔化成形18Ni300钢的冲击韧性均有显著影响,随着激光体能量密度的增加,18Ni300钢的冲击韧性不断增加,在激光体能量密度达到120 J·mm^(-3)后,冲击韧性趋于平稳。     

激光选区熔化镍基高温合金GH4169的成形工艺与显微组织研究

开展了基于激光选区熔化技术对镍基高温合金GH4169成形工艺的研究。研究了激光扫描速度和激光功率对成形试样组织的影响,及激光加工工艺参数对试样显微组织、致密化行为的影响。结果表明:当激光扫描速度一定,激光功率较低时,熔池的球化效应明显,材料内部形成较多孔洞,致密度较低;随着激光功率的提高,熔池内金属溶液表面张力减小,球化效应明显减弱,致密度随之提高。当激光功率一定,扫描速度较低时,金属溶液补缩能力强,材料组织致密,仅存在少量气孔;随着扫描速度的提高,熔池变窄变浅,相邻熔道及层间材料缺陷明显增多。当激光束能量密度较高时,粉末吸收能量较多,熔池温度高,凝固速率低,易形成粗大的柱状晶。在优化工艺参数下(激光功率335 W、激光扫描速率680 mm/s),成形体的致密度最高(98.7%)。     

选区激光熔化316L扫描特征参数对表面形貌影响

为研究不同扫描特征参数组合对选区激光熔化(selective laser melting,SLM)表面形貌的影响,以316L不锈钢粉末为例,进行介观尺度的单层双道数值模拟研究.基于离散元法建立单层的粉床数值模型.使用流体体积法对粉床受热部分粉末的熔化过程中的熔化、流动和凝固过程进行计算.考虑激光功率、扫描速度和扫描间距3个扫描特征参数,设计并进行正交试验,从熔道形貌特征和熔道宽度2个方面研究所选扫描特征参数对成形件表面的熔道形貌影响.依据数值模拟中的参数进行实际打印及形貌观察试验,验证数值模拟的有效性.结果表明,在313～500 J/m的线能量密度和50～90μm的扫描间距范围内,可以得到平整连续局部缺陷少的熔道形貌,且该区间内的参数组合依次线性对应;对熔道形貌的完整性影响由大到小依次为扫描速度、扫描间距和激光功率.     

AlSi10Mg粉末激光选区熔化温度场的数值模拟

使用有限元软件Ansys模拟Al Si10Mg激光选区熔化过程的温度场。考虑材料的热物性参数及激光能量吸收率随温度变化的特性,将激光热源视为三维高斯体热源,实现在粉床上的移动加载,实时进行材料由粉末态转化为实体态的单元属性转变,研究激光功率、扫描速度及扫描间距对粉床热行为的影响。结果表明:熔池最高温度、熔池尺寸及冷却速度随激光功率的增大逐渐增大;熔池最高温度与熔池尺寸随扫描速度的增大逐渐减小,熔池冷却速度随扫描速度的增大逐渐增大;扫描间距对熔池的最高温度、冷却速度及熔池尺寸影响不大,但扫描间距过大容易形成孔洞缺陷。     

AlSi10Mg铝合金选区激光熔化热行为的数值研究

利用ANSYS有限元分析软件建立了选区激光熔化(SLM)的单层多道的三维温度场有限元模型,针对AlSi10Mg铝合金材料进行模拟,研究了扫描速度对AlSi10Mg铝合金选区激光熔化热行为的影响。结果表明:随扫描时间的增加,由于前一扫描道对后一扫描道的热积累效应,后一扫描道上监测点的熔池温度越来越高,尺寸越来越大。随扫描速度的增加,同一监测点的熔池最高温度、尺寸和液相存在时间都逐渐减小,熔池沿扫描方向和垂直扫描方向的温度梯度略微增大。试验结果与数值模拟结果吻合良好。     

能量输入对SLM成形金属零件致密度的影响

研究了选区激光熔化(SLM)成形单熔道的形态及其形成原因:随着扫描速度的增加,单熔道形态逐渐从连续态过渡到断续态、球化态.在单熔道成形基础上进行正交试验,并讨论了SLM成形高致密度金属零件的能量输入条件及其对成形零件致密度的影响:当能量输入低时,致密度随着能量输入的增加迅速增大;随着能量输入的增加,致密度增加缓慢,进入...     

ZL114A合金的SLM成形性研究

为了探究选区激光熔化(SLM)成形ZL114A合金的可行性,研究SLM成形工艺参数对ZL114A铝合金的熔池形貌、表面品质和润湿角的影响。结果表明,扫描速率一定时,熔池熔宽随激光功率增大而增大;线能量密度相等,熔宽也相等。扫描速度为2 500 mm/s,375～475 W下熔道轨迹的连续性和延展性最好,球化等缺陷也较少。确定激光功率为450 W,扫描速度为2 500 mm/s,扫描间距为0.09 mm,层厚为50μm时,润湿角小,熔池高度较小,润湿性好,成形件致密度达到99.94%。     

选区激光熔化成形Inconel 718合金孔隙缺陷的研究

目的 研究选区激光熔化成形Inconel 718合金的孔隙缺陷,对缺陷进行科学分类并探究其形成机制,建立熔池溅射特征与缺陷形貌的对应关系,优化工艺参数,抑制缺陷产生。方法 采用扫描电子显微镜（SEM）、能量色散X射线光谱仪（EDX）分别对Inconel 718粉末的显微组织和化学成分进行观测,使用数字视频显微镜分析成形件内部缺陷,利用高速摄像机拍摄金属液滴的动态飞溅过程,并定量分析溅射特征参数。结果 随着激光功率的增大,能量密度升高,总的溅射数量增大,孔隙数量增多;当扫描速度增大时,能量密度降低,总的溅射面积减小,孔隙尺寸变小。当缺陷的圆度Circ≥0.731或纵横比AR≤1.368时,缺陷形貌由不规则向规则演变。当能量密度E=95.24 J/mm3时,相对致密度达到99.94%。经测量,所有样品的孔隙率和孔隙尺寸的平均值分别为2.249%和2.774 μm2。结论 孔隙缺陷可分为不规则的匙孔缺陷和规则的气孔缺陷两类,存在发生演变的圆度/纵横比门槛值。熔池震荡引起溅射特征变化,对应产生不同形貌特征的缺陷。减小激光功率和增大扫描速度可降低能量密度,使熔池震荡程度减弱,从而抑制缺陷产生,提高成形件的相对致密度。     

激光烧结工艺参数对Fe-16%Ni合金致密度的影响

采用激光烧结成形技术研究了不同工艺参数对Fe-16%Ni金属粉末选区激光烧结成型件微观结构和致密性的影响。结果表明,随着脉冲宽度、扫描速度和铺粉厚度的增加,烧结后试样的密度先增加然后减少,随着扫描间距的增加,烧结后试样的密度减小。当脉冲宽度0.7 ms,扫描速度1000 mm/min,铺粉厚度0.15 mm,扫描间距0.15 mm时,烧结成型件成型质量较好。     

Finite element analysis of temperature and stress fields during selective laser melting process of Al–Mg–Sc–Zr alloy

A 3D finite element model was established to investigate the temperature and stress fields during the selective laser melting process of Al–Mg–Sc–Zr alloy. By considering the powder–solid transformation, temperature- dependent thermal properties, latent heat of phase transformations and molten pool convection, the effects of laser power, point distance and hatch spacing on the temperature distribution, molten pool dimensions and residual stress distribution were investigated. Then, the effects of laser power, point distance and hatch spacing on the microstructure, density and hardness of the alloy were studied by the experimental method. The results show that the molten pool size gradually increases as the laser power increases and the point distance and hatch spacing decrease. The residual stress mainly concentrates in the middle of the first scanning track and the beginning and end of each scanning track. Experimental results demonstrate the accuracy of the model. The density of the samples tends to increase and then decrease with increasing laser power and decreasing point distance and hatch spacing. The optimum process parameters are laser power of 325–375 W, point distance of 80–100 μm and hatch spacing of 80 μm.     

Formation of scanning tracks during Selective Laser Melting (SLM) of pure tungsten powder: Morphology,geometric features and forming mechanisms

Due to the high melting point and high heat conductivity, selective laser melting (SLM) of tungsten is still challenging. To have a better understanding of SLM tungsten parts, the effects of processing parameters such as laser power and scanning speed on scanning tracks formation of pure tungsten powder were investigated. As linear energy increased with increasing laser power and decreasing scanning speed, the height and contact angle of scanning tracks gradually reduced, while the width and penetration depth increased. Owing to the good wetting and spreading, the flow front of scanning tracks gradually became smooth and stable with the increased linear energy. However, the transverse cracks induced by large temperature gradient and high cooling rate appeared on the surface of the scanning tracks at linear energy of more than 1.75 J/mm. A maximum temperature of 4630.27 °C and high cooling rate of 8.6 × 10⁶ °C/s were obtained during SLM process of tungsten powder when the linear energy was 1.75 J/mm. This work provides scientific guidance for SLM-processed tungsten parts.     

Influence of laser parameters on segregation of Nb during selective laser melting of Inconel 718

A transient three-dimensional powder-scale model was established for understanding the flow field and mass transfer within the molten pool during the selective laser melting (SLM) of Inconel 718 alloy by considering some important physical phenomena, such as, a transition from powder to solid, nonlinearities produced by temperature-dependent materials' properties, and fluid flow in the calculation. The influence of laser power or scanning speed on the flow field and cooling rate was discussed in detail. The simulation results reveal that the motion of molten pool and higher cooling rate promote the mass transfer and benefit the solute distribution by increasing laser power. However, with increasing the scanning speed, the melt flow speed and cooling rate are elevated, resulting in an agglomeration of the solute elements, which is ascribed to the shorter dwelling time of liquid. Therefore, the segregation of Nb can be effectively suppressed by increasing laser power or decreasing scanning speed, which can decrease the dwelling time of liquid.     

AlSi7Mg合金选区激光熔化工艺及性能研究

为了研究AlSi7Mg合金选区激光熔化成形工艺及性能,通过改变激光功率和扫描速度,得到不同工艺参数对成形试样性能的影响规律。结果表明:试样的相对密度随激光功率和扫描速度的增大均呈先上升后下降的趋势,试样的相对密度最高可达99.95%;随激光功率的增加,试样的拉伸性能先上升后下降;激光功率为350W、扫描速度1400 mm/s时,试样抗拉强度为423 MPa,屈服强度为293 MPa。     

SLM成形Cu6AlNiSnInCe仿金合金的工艺优化及其组织与性能

采用激光选区熔化(SLM)工艺成形Cu6AlNiSnInCe仿金合金,研究不同SLM工艺参数组合对试样成形质量及其组织和性能的影响。结果表明,根据SLM成形试样的形貌特征可将激光功率和扫描速度的影响直观地划分为六个区域,分别是过熔区、完全熔化区、球化区、部分熔化区、严重球化区和未成形区。在完全熔化区时,激光能量密度达到156 J/mm3,仿金粉末在该参数区域完全熔化且熔池保持稳定的状态,试样密度较高、表面质量较好,表面粗糙度为9.2μm;SLM试样由基体α-Cu(Al Ni)相和弥散分布在基体中的析出δ-Cu41Sn11相组成;SLM试样的抗变形能力、显微硬度和耐腐蚀性能均优于铸造试样。     

Investigation of laser consolidation process for metal powder by two-color pyrometer and high-speed video camera

This paper deals with the measurement of surface temperature on metal powder during the laser consolidation process with two-color pyrometer. Additionally, the aspect of selective laser sintering (SLS) and selective laser melting (SLM) of metal powder is visualized with high speed video camera. As a result, the surface temperature during the laser irradiation was ranged 1520–1810 °C and the consolidation phenomena was classified according to the melting point of metal powder. The metal powder at the heating process cohered intermittently to the melt pool although the laser beam was continuously irradiated to the powder surface.     

钛合金激光表面氮化层成形特征及分析

利用半导体激光器在氮气气氛中对钛合金表面进行氮化,为了研究线能量,激光功率和扫描速度对Ti-6Al-4V合金氮化层表面成形,熔池几何形貌,熔宽,熔深及成形系数的影响,采用光镜,扫描电镜拍摄氮化层表面成形及其横截面形貌,用显微硬度计测量氮化层硬度值。结果表明氮化层表面形貌由表面光滑和表面粗糙型两种区域组成。熔池表面温度较低时,增加激光束与基材的相互作用时间,对表面成形影响不大。相同线能量下随激光功率增大,氮化层熔深熔宽均呈增大趋势,成形系数减小;当激光功率相同时,随扫描速度减小,熔深熔宽均呈增大趋势,成形系数减小;成形系数很小时氮化层会产生沿纵向分布的裂纹。对流形式及强弱导致形成不同的界面形态,如：半球形界面,指状界面和W形界面等,而且熔合界面会发生多次弯曲。     

Achieving Superior Strength and Ductility of AlSi10Mg Alloy Fabricated by Selective Laser Melting with Large Laser Power and High Scanning Speed

AlSi10Mg alloy was prepared by selected laser melting(SLM) in a high laser power range 300–400 W. The effects of energy density on the relative density, microstructure and mechanical properties of the SLMed AlSi10Mg alloy were studied. The results showed that the SLMed AlSi10Mg alloy fabricated at a laser power of 400 W and a scanning speed of 1800 mm/s had a relative density of 99.4%, a hardness of 147.8 HV, a tensile strength of 471.3 MPa, a yield strength of 307.1 MPa, and an elongation of 9....     

旁轴送粉式激光扫描熔覆工艺研究

以Q235钢为基板,采用IPGYLS-4000型光纤激光器以及旁轴送粉器,搭建旁轴同步送粉式激光扫描熔覆工艺试验平台,在基板上进行熔覆试验。研究了激光功率、扫描速度和扫描宽度对熔覆层成形尺寸和对熔覆层组织的影响,结果表明:随着激光功率增大,铁基合金粉末熔化量提高,单层金属熔覆层的余高增加;扫描速度对熔覆层熔宽和余高的影响均较大,随着扫描速度的降低,金属熔覆层熔宽余高均增加,裂纹数量增多。约束应力是导致熔覆层出现裂纹的主要原因,通过优选工艺参数可以获得工艺良好无裂纹熔覆层,为下一步研究激光扫描多层熔覆无(小)变形焊接技术提供理论和技术依据。