纳米WC增强选区激光熔化AlSi10Mg显微组织与力学性能EI北大核心CSCD

为了进一步增强选区激光熔化(SLM)成型AlSi10Mg合金的性能,采用物理混合方法混合纳米WC与AlSi10Mg得到WC质量分数为0.1%的WC/AlSi10Mg复合材料,利用选区激光熔化成型机制备试样块。通过对比同种工艺制备的AlSi10Mg试样,探究纳米WC对其微观组织形成、演变规律及其组织对力学性能的影响。结果显示,WC/AlSi10Mg粉末球形度好,粒度分布集中在20~60μm。WC/AlSi10Mg试样致密度达到99%以上,硬度约为158.89HV,相比AlSi10Mg试样增加了14.58%。WC/AlSi10Mg试样组织生长均匀、致密,有明显的熔池线。晶粒内部为α-Al基体,边界为夹杂着WC的共晶Si相。WC/AlSi10Mg试样屈服强度达到337.75 MPa,抗拉强度高达514.00 MPa,伸长率为3.78%,相比同种工艺AlSi10Mg试样分别增加了4.73%,6.25%和35.97%。因此,SLM成型WC/AlSi10Mg纳米复合材料零件相比AlSi10Mg零件具有更好的应用前景。     

激光选区熔化纳米SiC/AlSi7Mg复合材料微观组织及力学性能EI北大核心CSCD

采用机械混合法制备纳米SiC/AlSi7Mg混合粉末,利用激光选区熔化技术(selective laser melting,SLM)成形纳米SiC颗粒增强AlSi7Mg复合材料,观察和分析试样的相对密度、物相和微观组织,并测试材料的硬度和拉伸性能。结果表明:SLM成形纳米SiC/AlSi7Mg复合材料试样的相对密度随着扫描速度和扫描间距的增大均呈现先增加后减少的趋势,相对密度最高可达99.75%;试样微观组织与SLM成形铝合金相似,Si相呈网状结构均匀嵌入α-Al基体中,且在Al基体中存在与Si分布相似的纳米SiC团聚物及Mg_(2)Si相;与AlSi7Mg相比,复合材料微观组织由柱状晶转化为等轴晶,且晶粒明显细化(平均晶粒尺寸为1.36μm);由于SiC的加入,产生细晶强化和固溶强化,试样的硬度和强度均明显提高,硬度最高达到137.3HV,抗拉强度达到448.3 MPa,屈服强度达到334.7 MPa,但伸长率下降至3.9%,断裂模式主要为脆性断裂。     

激光选区熔化成形含钛6061铝合金的显微组织与力学性能EI北大核心

激光选区熔化(selective laser melting,SLM)成形6061铝合金易形成粗大的柱状晶和热裂纹。采用低能球磨组装修饰法制备TiH_(2)/AA6061铝基复合粉末,采用激光选区熔化技术制备含钛6061铝合金试样,分析不同TiH_(2)添加量对试样显微组织和力学性能的影响。结果表明:添加1%TiH_(2)(质量分数,下同)即可使合金熔池边界形成连续的等轴晶区,平均晶粒尺寸从59.8μm减小到2.53μm,粗大的柱状晶粒和裂纹被抑制,添加1.5%TiH_(2)时,SLM试样的粗大柱状晶组织绝大部分消失。显微组织转变归因于Ti元素增强成分过冷以及原位反应形成L12-Al_(3)Ti形核质点,该质点与铝基体形成共格界面,具有较强的异质形核作用,显著促进Al基体柱状晶向等轴晶转变及晶粒细化。经激光选区熔化成形后,添加1%TiH_(2)的试样抗拉强度为274 MPa,屈服强度为238 MPa,断后伸长率为18%。     

热处理对激光选区熔化成型316L合金综合性能的影响

为获得力学性能优良的316L合金,研究了激光选区熔化(SLM)成型316L合金试样在400℃/2 h、900℃/2 h、1050℃/2 h热处理后的微观组织与力学性能.使用拉伸试验机和冲击试验机分别对试样进行拉伸和冲击实验;用数显硬度计测试316L合金在不同热处理工艺下的硬度差别,通过光学显微镜和SEM观察试样的断裂表面组织形貌,分析断裂机理.采用电子背散射衍射仪观察热处理前后晶面的相位变化.结果表明:SLM成型试样在900℃/2 h水冷条件下,抗拉强度最高达到680 MPa;在1050℃/2 h水冷条件下,试样具有最大(18％)的延伸率;试样的硬度随着热处理温度的升高呈现出先升高后降低的趋势.未处理的SLM成型试样沿沉积方向形成柱状晶粒,但经处理的试样随着热处理温度的升高,合金元素固溶重组,晶面位向差减小,得到较均匀的各向同性配置.     

热处理工艺对激光选区熔化AM247LC合金组织与性能的影响规律

目的 研究不同热处理制度对激光选区熔化（SLM）AM247LC合金微观组织和力学性能的影响规律。方法 对激光选区熔化制备的AM247LC合金分别进行900℃/16h的直接时效热处理和1 210℃/30 min+1 050℃/30min+950℃/16h的固溶时效热处理,通过OM、SEM、EBSD、XRD等表征手段研究合金热处理前后的晶粒组织、碳化物及析出相等微观组织的变化,并对打印态及不同热处理态样品的室温拉伸性能进行测试,以表征热处理对其力学性能的影响行为。结果 打印态AM247LC合金中存在大量粗大柱状晶和细小晶粒组织;直接时效热处理（900℃/16 h）后的AM247LC合金晶粒组织与打印态类似,但析出了大量γ’强化相;固溶时效热处理（1 210℃/30 min+1 050℃/30 min+950℃/16 h）后,AM247LC合金发生了再结晶,形成大量退火孪晶,并且析出沿晶界分布非连续的微米级碳化物及大量γ’强化相。合金打印态的屈服强度为846.5 MPa,断裂伸长率可达19.6%;直接时效热处理后,合金屈服强度为1 042.8 MPa,断裂伸长率明显降低,仅为11.2%;固溶...     

镁合金激光选区熔化研究进展

镁合金作为最轻的金属结构材料,在汽车制造、生物医疗等领域具有极大的应用潜力。激光选区熔化成形镁合金具有高效的制备性能、良好的成分均匀性、优异的力学性能和耐腐蚀性能,因此激光选区熔化成为一种重要的镁合金制备和改性方法。对近几年激光选区熔化镁合金的研究进展进行了综述,从激光工艺参数(激光类型、体能量密度、激光功率、扫描速度、扫描模式、层厚、扫描间距、气氛控制与进粉速度)和粉体状态(粉末形状、粒径分布、粉末对激光束能量吸收率、粉末化学成分)2个方面讨论了该工艺的关键技术;按照纯镁、非稀土镁合金体系、稀土镁合金体系的分类,对激光选区熔化成形镁及镁合金的致密度与微观结构、力学性能与耐腐蚀性能进行了总结;分析了工艺参数与合金成分两方面对该工艺成形镁合金缺陷的影响。为减少激光选区熔化成形镁合金缺陷、均匀化晶粒、溶解硬脆二次相或析出强化相进而改善合金的结构与性能,许多研究对激光选区熔化成形镁合金进行了热等静压、固溶热处理和时效热处理,总结了上述处理方式对AZ体系、WE体系与Mg-Gd体系镁合金的改善效果。最后展望了激光选区熔化成形镁及镁合金在各领域的应用前景与未来可以进行研究的方向。     

选区激光熔化成形铜合金研究进展

铜合金具有良好的导电导热性,是众多行业的基础材料,随着高新技术的迅速发展,许多行业对高性能、高精度、复杂结构铜合金零部件需求日益增大。传统工艺可制备常规铜合金零件,但对于一些复杂结构铜合金零部件的制备存在困难。首先,本文综述了选区激光熔化成形铜及铜合金的研究进展,系统介绍了目前选区激光熔化成形纯铜所遇到的难点及解决方法;然后,综述了目前选区激光熔化成形不同系列铜合金的研究现状,重点介绍了不同系列铜合金成形件微观组织和力学性能及热处理后成形件微观组织和力学性能变化;最后总结了选区激光熔化成形铜及铜合金存在的问题及未来的研究方向。     

激光选区熔化颗粒增强钛基复合材料的抗压性能EI北大核心CSCD

采用激光选区熔化(selective laser melting,SLM)制备LaB_(6)颗粒增强钛基复合材料,研究不同激光能量密度下试样的致密化行为、显微组织、物相及其在准静态和动态冲击条件下的力学性能。结果表明:LaB_(6)颗粒的加入在一定程度上改变了材料的致密化行为,过高或者过低的激光能量密度均会降低试样的致密度。而增强颗粒的加入细化了基体材料的晶粒,钛合金的初始β晶粒及针状α晶粒的晶界有一定程度的弱化,从而导致复合材料的屈服强度和极限强度增加,但延展性降低,同时复合材料表现出明显的应变率强化效应。与SLM成型Ti-6Al-4V合金相比,复合材料在塑性段的应变硬化效应和失稳阶段的脆性断裂特征更显著,为激光增材制造高性能颗粒增强钛基复合材料的动态抗压性能优化提供理论基础。     

选区激光熔化铝合金缺陷的形成机制和对力学性能的影响:综述

选区激光熔化(Selective laser melting,SLM)作为增材制造(Additive manufacturing,AM)技术的一种,其成形精度高,有利于实现更复杂的结构设计,适合铝合金复杂零部件的快速成形,被广泛应用于航空航天领域中.铝合金由于具有密度小、比强度高及优良的综合力学性能被广泛应用于航空航天、汽车等轻量化设计领域中.但是打印缺陷的形成严重限制了SLM工艺铝合金的推广应用.因此,了解缺陷的形成机制从而控制缺陷的产生对SLM工艺铝合金的应用有着重要的意义.SLM工艺打印缺陷主要分为裂纹,孔隙,残余应力和各向异性,球化.打印缺陷主要由不恰当的工艺参数导致.本文以Al-Si系铸造铝合金为研究对象,综述了SLM制备铝合金打印缺陷形成机制的研究进展,总结了缺陷形成的影响因素,并归纳了缺陷与铝合金力学性能之间的影响关系,孔隙率过多容易导致铝合金的拉伸和疲劳性能降低,通过选择适当的后处理可以有效改善其疲劳性能.     

热处理对选区激光熔化17-4PH不锈钢力学性能的影响

对选区激光熔化成形的17-4PH不锈钢分别进行真空热处理、热等静压高压淬火处理和组合热处理(热等静压固溶后快淬和马弗炉时效后水冷),在1040℃固溶处理2 h和在480℃时效4 h,观察其显微组织并研究了热处理对其力学性能的影响。结果表明,17-4PH不锈钢由回火马氏体和淬火马氏体组成,热处理后沉淀相弥散分布于晶粒内部,其颗粒尺寸为100~150 nm。真空热处理使合金内部孔隙的尺寸减小到3~7 μm,而热等静压使内部孔隙几乎完全闭合,使钢的密度基本上达到理论值。真空热处理+水淬使沉积态17-4PH不锈钢的抗拉强度和硬度都显著提高(分别提高到1300 MPa和448.5HV);热等静压在提高沉积态17-4PH不锈钢抗拉强度的同时使其延伸率显著提高到22.4%。断口分析结果表明,沉积态和热等静压样品的断口形貌为典型的韧性断裂,热等静压样品的韧窝更深、尺寸更大。真空热处理和组合热处理样品的断口形貌具有部分脆性断裂的特征且出现裂纹,与沉积态相比塑性略有降低。     

Effect of different heat treatments on the microstructure and mechanical properties in selective laser melted INCONEL 718 alloy

The microstructure and tensile properties of selective laser melted (SLM) Inconel 718 alloy were studied in the as-printed and different heat treat conditions. The SLM as-print microstructures exhibited columnar grain structures with very fine dendritic structure with segregation of elements. Apart from the standard heat treatment, three other heat treat cycle variants were carried out in an attempt to remove the extensive segregation of elements and modify the textured grain structure of the SLM as-print microstructure. Increasing the homogenization temperature reduced the segregation and coarsened the grain structure. However, the grains still remained columnar, and the material became softer with reduction in strength. After the ageing treatment, the tensile strength improved significantly for all the heat treated samples, which is typical for precipitation hardening of IN718 alloy. The microstructures of the heat treated samples exhibited the needle shaped δ, carbides, and finely dispersed γ″, γ′ phases.     

Weldability,microstructure and mechanical properties of laser-welded selective laser melted 304 stainless steel joints

Laser welding is a promising process for joining small components produced by selective laser melting (SLM) to fabricate the large-scale and complex-shaped parts. In the work, the morphology, microstructure, microhardness, tensile properties and corrosion resistance of the laser welded stress-relieved SLMed 304 stainless steel joints are investigated, as the different sections of stress-relieved SLMed 304 stainless steel are joined. Results show that the SLMed 304 stainless steel plates have a good laser weldability. The microstructure of laser-welded joints consists of the cellular dendrites in austenite matrix within columnar grains, exhibiting a coarser dendrite structure, lower microhardness (∼220 HV) and tensile properties (tensile strength of ∼750 MPa, and area reduction of ∼27.6%), but superior corrosion resistance to those of SLMed plates. The dendrite arm spacing of the joints varies from ∼3.7 μm in center zone, to ∼5.0 μm in fusion zone, to ∼2.5 μm in epitaxial zone. The SLMed anisotropy shows a negligible effect on the microstructure and performance of the laser-welded joints. The laser welding along the building directions of the SLMed base plates can induce a slightly finer dendritic structure and higher tensile properties.     

Mechanical properties and corrosion behavior of selective laser melted 316L stainless steel after different heat treatment processes

Irregular grains, high interfacial stresses and anisotropic properties widely exist in 3D-printed metallic materials, and this paper investigated the effects of heat treatment on the microstructural, mechanical and corrosion properties of 316 L stainless steel fabricated by selective laser melting. Sub-grains and low-angle boundaries exist in the as-received selective laser melted (SLMed) 316 L stainless steel. After heat treatment at 1050 °C, the sub-grains and low-angle boundaries changed slightly, and the stress state and strength decreased to some extent due to the decrease of dislocation density. After heat treatment at 1200 °C, the grains became uniform, and the dislocation cells vanished, which led to a sharp decline in the hardness and strength. However, the ductility was improved after recrystallization heat treatment. The passive film thickness and corrosion potential of the SLMed 316 L stainless steel decreased after heat treatment, and the pitting potential also decreased due to the accelerated transition from metastable to steady-state pitting; this accelerated transition was caused by the presence of weak passive films at the enlarged pores after heat treatment, especially for an adequate solid solution treatment.     

热处理对6005A铝合金激光焊接头组织和性能的影响

高速列车车体轻量化制造的迫切需求,使得铝合金结构在车体制造中得到广泛应用,而铝合金焊接也成为高铁车体制造的关键工艺.本文采用激光填丝焊方法焊接6005A-T6铝合金,并对焊接接头进行了固溶/时效热处理.利用扫描电镜、XRD能谱分析及拉伸实验,对焊后热处理的焊接接头组织及性能进行研究.研究发现,与母材相比,由于焊接接头中...     

Effects of processing parameters on tensile properties of selective laser melted 304 stainless steel

Selective laser melting (SLM) technology based on powder bed has been used to manufacture 304 stainless steel samples. The effects of slice thickness, overlap rate, building direction and hatch angle on tensile properties of SLMed 304 stainless steel samples are investigated. It is found that tensile properties of SLMed 304 stainless steel are independent of slice thickness and overlap rate, but increase slowly with increasing interval number of deposited layers. The hatch angle of 105° with the maximum interval number of deposited layers and vertical building direction are preferred to get excellent tensile properties. Importantly, all the SLMed samples feature much higher σ_0.2/UTS values of nearly 0.8. The tensile strengths and ductility of SLMed samples at proper parameters are higher than those of the wrought 304 stainless steel.     

稀土变质及热处理对高碳铬铸钢力学性能影响

研究了稀土变质与热处理对高碳铬铸钢力学性能的影响.采用金相显微镜、扫描电子显微镜观察了试样碳化物的形貌、冲击断口及磨面特征,用公式s=20.3 z/P2计算了碳化物的形状因子;采用冲击试验机、万能试验机等测试了试样的冲击韧性、抗弯强度、挠度;用动载磨损试验机对试样进行了磨损试验.结果表明:高碳铬铸钢经0.22％稀土变质后再经960℃×3 h正火,其冲击韧性提高180％,,抗磨性提高20％,强度提高76％,塑性也有所提高.其主要原因在于稀土变质及热处理使高碳铬铸钢组织中连续网状的共晶碳化物转变为孤立的块状、碳化物的形状因子增大以及粒状碳化物的析出所致.     

热处理工艺对AFA耐热钢组织和力学性能的影响

为考察热处理工艺对AFA耐热钢组织和力学性能的影响,本文利用光学显微镜、扫描电镜、X射线衍射等技术,研究了新型含铝奥氏体耐热钢(AFA)在不同保温温度和冷却方式下的组织演变规律及力学性能的变化.结果表明:加热温度和冷却方式对试样的显微组织均产生影响.随着保温温度的升高,晶粒的平均尺寸逐渐增大.在1 150和1 200℃...     

退火态激光选区熔化成形AlSi10Mg合金组织与力学性能

AlSi10Mg合金具有高比强度、高耐磨性等优良特点。由于其成分接近共晶点,成形性能良好,被广泛应用于激光选区熔化技术。然而其热处理制度仍然沿用传统铸态合金的热处理规范,影响了其性能的充分发挥。本工作采用激光选区熔化技术制备了AlSi10Mg合金,并研究了沉积态和后续热处理过程中组织演化规律及其对室温力学性能的影响机制。研究发现：沉积态组织由沿沉积方向生长的α-Al柱状枝晶及枝晶间网状Al-Si共晶组成,具有强烈的〈100〉方向织构,沉积层由三部分组成,分别是细晶区、粗晶区及热影响区,抗拉强度389.5 MPa,伸长率4%。退火过程中,共晶Si破碎、球化,基体中过饱和Si不断析出长大。当退火温度从200 ℃提高到500 ℃时,Si颗粒发生Ostwald熟化,平均尺寸增长了23倍。经过300 ℃和500 ℃退火处理后,试样抗拉强度分别为287.0 MPa和268.0 MPa,但伸长率分别提高到10.3%和17.2%。     

Effect of heat treatment on mechanical and ballistic properties of a high strength armour steel

In the present study an ultra high strength armour steel was austenatised at 910°C followed by tempering at 200, 300, 400, 500 and 600°C. After heat treatment the properties of tensile strength, ductility, charpy impact strength, hardness and microstructure were evaluated from the mechanical tests and metallographic analysis respectively. The ballistic behavior of the heat-treated plates was evaluated impacting against non-deformable hard steel core projectiles at 840 ± 15 m/s at normal angle of attack. The changes in the microstructure and mechanical properties with heat treatment have been correlated with ballistic performance of the steel. Experimental results showed that 200°C tempering gives the best ballistic performance.     

The effect of laser energy input on the microstructure,physical and mechanical properties of Ti-6Al-4V alloys by selective laser melting

Selective laser melting is an advanced manufacturing process which can control the microstructure evolution and mechanical properties of as-manufactured products via various processing parameters. In this study, the porosity/relative density, surface quality, microstructure and mechanical properties were investigated on the selective laser melted Ti-6Al-4V alloy specimens fabricated with a wide range of laser energy inputs. It was found that the microstructure of selected laser melted Ti-6Al-4V alloys is typical of acicular martensites α′. Quantitative analysis reveals that the relative density, martensitic lath size and microhardness increase with the laser energy input. The surface quality is also substantially affected by the energy input.