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。     

激光熔化沉积铝合金显微组织及力学性能

目的 提高激光熔化沉积铝合金的成形质量。方法 以颗粒度45~105 μm的AlSi10Mg粉末为材料,4045铝合金为基板,利用激光熔化沉积设备在充氩舱内进行铝合金成形试验。测试试样的硬度和拉伸性能,并通过扫描电子显微镜和光学显微镜进行显微组织形貌分析。结果 在沉积方向上,试样显微组织呈现周期性条带状纹路,搭接区域呈现出比较明显的弧形特征;含有大量的细密树枝晶。该合金相成分主要包括:Al相、共晶Si相及少量的Mg2Si强化相。沿扫描方向,试样平均硬度值约为130HV;沿沉积方向,试样平均硬度值约为100HV;沉积态试样的屈服强度约为185.75 MPa,伸长率约为15.21%;沉积态试样拉伸性能明显优于压铸试样;该铝合金的失效形式为韧性断裂。结论 AlSi10Mg在激光熔化沉积时具有良好的成形能力,沉积态的组织强度高于铸态组织强度。     

激光选区熔化AlSi7Mg合金的微观组织和力学性能

利用激光选区熔化(Selective laser melting, SLM)成形技术对AlSi7Mg合金成形工艺进行研究,并对最佳工艺参数成形沉积态和热处理试样微观组织和力学性能进行分析。结果发现:沉积态试样抗拉强度、屈服强度和延伸率均明显高于铸态性能,横向试样分别达到435.78 MPa、299.23 MPa和14.36%。热处理对SLM试样的微观组织和力学性能影响很大,350℃、3 h退火工艺下,试样延伸率增加到30.83%,抗拉强度和屈服强度分别下降到210.35 MPa和152.01 MPa。本工作表明,可以通过改变工艺参数和热处理控制晶粒尺寸和形状,以获得所需微观组织和力学性能的合金。     

粉体性能及选区激光熔化打印工艺对AlSi10Mg合金致密化行为的影响

本研究重点探索了AlSi10Mg合金的粉体性能以及选区激光熔化(SLM)打印工艺对AlSi10Mg合金粉体致密化行为的影响。通过对两种粒度组成不同的球形AlSi10Mg合金粉体在选区激光熔化(SLM)工艺过程中致密化行为的研究,发现AlSi10Mg粉体粒度组成对SLM打印过程中的致密化程度有关键性影响:粗粉含量较高,更有利于较高致密度的SLM打印件的制备。通过选取上述两种粉体中SLM打印性能较高的AlSi10Mg粉体,采用Box-Behnken响应曲面实验设计系统探索了SLM工艺参数对打印件致密度的影响规律,获得了SLM打印工艺参数与打印件相对密度的定量关系模型。研究发现,SLM打印参数中对AlSi10Mg合金相对密度的影响程度从大到小依次为:激光功率、扫描速度、扫描间距;当激光功率为375 W、扫描速度为2 000 mm/s、扫描间距为50μm时,AlSi10Mg打印件的相对密度值可达到98.26%,抗拉强度可达487 MPa。     

激光选区熔化成形原位自生TiB2/Al-Si复合材料的微观组织和力学性能

利用激光选区熔化（SLM）技术制备了原位自生TiB₂纳米陶瓷颗粒增强Al-Si基复合材料,并对成形后的TiB₂/Al-Si复合材料进行不同的热处理。通过XRD物相分析、SEM微观组织观察、电子背散射衍射（EBSD）、EDS元素扫描分析和力学拉伸试验等对TiB₂/Al-Si复合材料的微观组织进行观察和力学性能测试。研究表明,在原位自生TiB₂纳米陶瓷颗粒和SLM快速凝固特性的共同作用下,SLM成形的原位自生TiB₂/Al-Si复合材料具有超细晶结构,平均晶粒尺寸为1.1 μm;TiB₂/Al-Si复合材料的力学性能优异,屈服强度为262 MPa,抗拉强度为435 MPa,延伸率为11.88%。对比经不同热处理的TiB₂/Al-Si复合材料,直接时效处理（150℃/12 h）的TiB₂/Al-Si复合材料性能最优,抗拉强度达到488 MPa,提高了53 MPa,延伸率降低至7.2%。     

激光增材制造24CrNiMo合金钢显微组织特征EI北大核心CSCD

采用激光选区熔化技术和激光熔化沉积技术制备24CrNiMo合金钢单道和块体样品,研究两种激光辐照条件下24CrNiMo低合金钢的相组成、微观组织、织构特征和显微硬度。结果表明:两种方法制备的24CrNiMo合金试样的相组成均为α-Fe相以及少量的Fe 3C;SLM成形单道沉积样品的晶粒取向随机、无序,无明显的择优取向,而LMD成形单道沉积样品的择优取向为(110)〈101〉面织构;SLM成形块体样品的晶粒在平行于沉积方向上存在较弱的〈111〉织构,LMD成形块体样品的晶粒存在外延生长取向为〈111〉的强织构;SLM成形试样的显微组织主要为下贝氏体,而LMD成形试样的显微组织以板条贝氏体为主;具有细小晶粒和下贝氏体组织的SLM成形试样的平均显微硬度高于LMD试样。     

Si_3N_4颗粒和纳米SiC晶须强韧化MoSi_2基复合材料

用真空热压法制备了Si3N4颗粒和纳米SiC晶须强韧化MoSi2基复合材料。采用X射线衍射仪、金相显微镜、扫描电镜分析了该材料的物相、微观组织结构和断口形貌,测算了其致密度、晶粒尺寸、抗弯强度和断裂韧性。结果表明:复合材料致密性好;添加的Si3N4和SiC与基体有着很好的化学相容性;与纯MoSi2相比,复合材料晶粒明显细化,抗弯强度和断裂韧性明显增加。其中MoSi2+20%Si3N4+10%SiC抗弯强度达400MPa,比纯MoSi2提高了58.7%;断裂韧性达6.1MPa.m1/2,比纯MoSi2提高了108.9%。复合材料的强化机制为细晶强化和弥散强化;韧化机制为细晶韧化、裂纹偏转和裂纹微桥接。     

TiB2/AlSi10Mg激光选区熔化成形工艺研究

目的 针对TiB2/AlSi10Mg开展激光选区熔化成形研究,获得工艺参数影响规律并优化工艺参数.方法 采用正交试验法设计三因素四水平正交试验,进行TiB2/AlSi10Mg激光选区熔化成形,分别研究激光功率、扫描速度、扫描间距等3种工艺参数对TiB2/AlSi10Mg致密度和硬度的影响规律,分析激光能量密度对铝合金内部缺陷的影响,并且研究时效时间对材料硬度的影响.结果 TiB2/AlSi10Mg激光选区熔化成形的最佳工艺参数:激光功率为280 W,扫描速度为1400 mm/s,扫描间距为90μm,层厚为30μm时,得到的材料致密度为99.7％,时效处理后的硬度为151HV.结论 工艺参数对于SLM成形TiB2/AlSi10Mg致密度的影响顺序为扫描间距>激光功率>扫描速度,对于硬度的影响顺序为扫描间距>扫描速度>激光功率;扫描间距对于致密度和硬度的影响程度均最大.     

纳米晶Mg2Si块体的制备及力学性能

采用机械激活固相反应及真空热压方法制备纳米晶Mg2Si金属间化合物块体材料.研究表明,过量Mg配量对获得纯相Mg2Si至关重要.在1.5GPa压力于450℃热压得到的纯相Mg2Si纳米块体(相对密度D～98%,晶粒度d～54nm)断裂韧性达1.67MPa·m1/2,较常规粗晶Mg2Si有明显提高.     

成形压力对SiC/TiB2复合材料组织与性能的影响

基于熔融Si浸渗法制备出较致密的SiC/TiB₂复合材料, 并研究了坯体成形压力对SiC/TiB₂复合材料致密度、相组成、显微组织和力学性能的影响。实验结果表明, 复合材料由TiB₂、SiC和Si相组成。SiC/TiB₂复合材料的显微组织特征为: TiB₂相和SiC相均匀分布, 游离Si填充在TiB₂相和SiC相的空隙处, 且形成了连续相。随成形压力的增大, 复合材料中游离Si含量降低, TiB₂颗粒尺寸减小, 复合材料的力学性能先增加后降低。坯体最佳成形压力为200 MPa, 对应SiC/TiB₂复合材料的体积密度、开口气孔率、抗弯强度、断裂韧性和维氏硬度分别为3.63 g/cm³、0.90%、(354±16) MPa、(6.8±0.2) MPa·m^1/2和(21.0±1.1) GPa。     

CNT-reinforced AlSi10Mg composite by selective laser melting: microstructural and mechanical properties

Carbon nanotube (CNT)-AlSi10Mg composites were fabricated by selective laser melting (SLM). The influence of CNTs on the density, microstructure, and strength of SLM CNT-AlSi10Mg composites was investigated. The addition of CNTs over 0.1?wt-% significantly damaged the density due to the high surface energy of the CNTs. The network Si eutectic had no significant difference in either the SLM AlSi10Mg alloy or the CNT-AlSi10Mg composite. Reserved CNTs with a short scale were observed in the SLM CNT(0.5?wt-%)-AlSi10Mg composite. The ultimate tensile strength of the 0.05?wt-% CNT-AlSi10Mg composite was 441.2?±?0.9?MPa, which was higher than that of AlSi10Mg alloy. The grain boundary strengthening played an important role in the reinforcement of CNT-AlSi10Mg composite because of the refined grain.     

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%。     

Microstructure evolution and mechanical properties at high temperature of selective laser melted AlSi10Mg

In this study,the microstructure and tensile properties of selective laser melted AlSilOMg at elevated temperature were investigated with focus on the interfacial region.In-situ SEM and in-situ EBSD analysis were proposed to characterize the microstructural evolution with temperature.The as-fabricated AlSilOMg sample presents high tensile strength with the ultimate tensile strength(UTS)of~450 MPa and yield strength(YS)of~300 MPa,which results from the mixed strengthening mechanism among grain boundary,solid solution,dislocation and Orowan looping mechanism.When holding at the temperature below 200℃for 30 min,the micro structure presents little change,and only a slight decrement of yield strength appears due to the relief of the residual stress.However,when the holding temperature further increases to 300℃and 400℃,the coarsening and precipitation of Si particles inα-Al matrix occur obviously,which leads to an obvious decrease of solid solution strength.At the same time,matrix softening and the weakness of dislocation strengthening also play important roles.When the holding temperature reaches to 400℃,the yield strength decreases significantly to about 25 MPa which is very similar to the as-cast Al alloy.This might be concluded that the YS is dominated by the matrix materials.Because the softening mechanism counteracts work hardening,the extremely high elongation occurs.     

Preparation for Semi-Solid Aluminum Alloy Slurry under Weak Electromagnetic Stirring Conditions

The effects of pouring temperature, short electromagnetic stirring with low strength and then soaking treatment on the microstructure of AISi7Mg alloy were investigated. The results show that if AlSi7Mg alloy is poured at 630 or 650℃ and meanwhile stirred by an electromagnetic field at a low power for a short time, the pouring process can be easily controlled and most solidified primary α-Al grains become spherical and only a few of them are rosette-like. Weak electromagnetic stirring makes the temperature field more homogeneous and makes the primary α-Al grains disperse in a larger region, which leads to the spherical microstructures of primary α-Al grains. When the AISi7Mg alloy is soaked or reheated at the semisolid state, the primary α-Al grains ripen further and they become more spherical, which is favorable to the semi-solid forming of AlSi7Mg alloy.     

A new modification effect of eutectic Si in selective laser melted AlSi10Mg

A distinct modification of eutectic Si was observed in the selective laser melted AlSi10Mg. The eutectic Si particles were modified substantially and demonstrated a nanoscale size, a fibrous morphology with obvious ‘necking effect’. The modification mechanism and the influence of heat treatment on eutectic Si growth were explored. It was suspected that Si experienced the necking effect under a tensile environment due to the large temperature gradient and α-Al erosion during the SLM process. Upon heat treatment, the Si particles were spheroidised and distributed homogeneously. Under the synergistic action of Si crystal fragmentation and the continuous precipitation of saturated Si from the Al matrix, the coarsened and spheroidised eutectic Si were distributed homogeneously in the Al matrix.     

Zr含量对铸造AlSi7Mg0.4合金力学性能的影响

研究了添加Zr元素的重力铸造AlSi7Mg0.4合金的微观组织和力学性能。结果表明,在含Zr的铸态合金中生成了(Al,Si)₃(Zr,Ti)和π-Fe相,Zr的添加使合金的晶粒尺寸减小;经过T6热处理后富Fe相中的Mg和少量粗大的(Al,Si)₃(Zr,Ti)相重溶到基体中,减小了金属间化合物的尺寸,生成了与基体有共格关系的含Zr析出相。含Zr合金的抗拉强度和伸长率达到332 MPa和8.7%,比不含Zr的合金分别提高了10%和90%。     

Phase analysis and microstructure characterisation of AlSi10Mg parts produced by Selective Laser Melting

ABSTRACT

Microstructural features of AlSi10Mg samples produced by Selective Laser Melting (SLM) technique were systematically characterised. The results showed that certain amount of Si dissolved in the Al matrix (face centre cubic) to form cellular-dendritic α-Al phase. These cells were approximated to be 500?nm. The lattice constant value was found to decrease, resulting from the solid solution of Si in α-Al. Along the boundary of these cells, Mg element clusters were also detected where X-Ray diffraction and energy dispersive X-ray spectroscopy results indicated that Mg₂Si dispersoid hardening phase was formed during the SLM process. In addition, the network features along the boundary of Al phase were identified to be eutectic Al/Si phase according to the transmission electron microscopy (TEM)–EDS result. Very fine grainy features of nanometric scale were observed within this phase with dimensions less than 5?nm.     

铸态Mg-4Al-4Si-0.75Sb合金的显微组织与力学性能

采用重力铸造法制备Mg-4Al-4Si-0.75Sb(AS44-0.75Sb)(质量分数/%,下同)镁合金,研究铸态合金的显微组织和室温力学性能。结果表明:铸态AS44-0.75Sb合金主要由α-Mg基体、β-Mg17Al12相、Mg2Si相和Mg3Sb2相组成;加入0.75Sb后形成高熔点的Mg3Sb2相,显著改善了Mg2Si相的形貌,使粗大的骨骼状Mg2Si转变为相对细小的汉字状Mg2Si。铸态合金的硬度HV为65.9,屈服强度为136.4MPa,抗拉强度为172.3MPa,伸长率为3.3%;拉伸断裂形式为准解理脆性断裂。     

Friction welding of Al–12Si parts produced by selective laser melting

Al–12Si samples produced by selective laser melting (SLM) are welded using solid-state friction welding. The weld metal shows the presence of texture with excess Si diffusing out from the Al matrix. Microstructural investigations reveal a pronounced change in the shape and size of the Si phase in the weld metal compared to the base material, with the formation of extremely fine particles uniformly distributed in the Al matrix. This variation in the microstructure is expected to have significant changes in the mechanical properties of the welded material. The hardness measurements reveal a drop of hardness in the weld zone with respect to the base metal. Similarly, the room temperature tensile tests show a significant improvement of ductility in the welded SLM samples. However, the yield and the ultimate strength show only a marginal drop in the welded samples compared to the as-prepared SLM specimens. The present work demonstrates that solid-state friction welding not only permits to successfully join materials produced by SLM, but also helps to significantly improve their ductility.