等离子喷涂成形钨喉衬的烧蚀性能

采用等离子喷涂成形结合热等静压技术制备内径8mm、长30mm、壁厚16.5mm的钨喉衬,测试喉衬在小型固体火箭发动机地面试车条件下的抗热震烧蚀性能.结果表明等离子喷涂成形钨喉衬为典型的柱状晶层片结构,致密度仅为85.6%;经二步热等静压处理后,喉衬样件仍为层片结构,层片间微观缝隙及大部分孔隙消失,致密度提高至96.7%;地面试车实验后,钨喉衬整体结构完好,未出现炸裂和破碎现象,具有良好的抗冲刷和耐烧蚀性能,其线烧蚀率仅为4μm/s.经SEM和XRD等检测发现,喉部以机械剥蚀为主,以熔化烧蚀及热化学烧蚀为辅,其烧蚀程度最为严重;收敛段为机械剥蚀和热化学烧蚀,其烧蚀程度次之;而扩散段则发生热化学烧蚀,其烧蚀程度最低.     

热锻对喷射成形7055铝合金组织性能的影响

利用喷射成形技术制备了7055高强铝合金。借助拉伸性能测试,电化学工作站、金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM) 等手段研究了热锻对挤压合金显微组织和性能的影响。结果表明：挤压合金的纵向抗拉强度达到642 MPa,屈服强度达到598 MPa,而锻造合金的抗拉强度和屈服强度却下降了,但延伸率、电导率和硬度有所上升,断口形貌均体现为韧性断裂;合金的主要元素在晶界和晶内的分布没有明显差别,但有所波动,且锻造后合金元素波动更明显;合金经过时效后晶内都均匀分布着GP区和η＇析出相,晶界η析出相则是断续的点状分布,但锻造后晶内析出相粗化,晶界析出相变多;锻造合金的耐蚀性比挤压合金有所提升。     

喷射成形CuCr25合金触头材料的致密化与性能

研究了喷射成形CuCr25合金沉积坯件的致密化处理工艺及其在860～1 070℃保温1 h后的组织演变,确定了热变形加工温度,研究了热锻压和热等静压后材料的组织、致密化以及电导率、密度、硬度等触头材料常规性能.结果表明:在1070℃保温1 h,触头材料未发生熔化,组织略微长大,但在正常范围内,经热锻压和热等静压处理后可实现致密化.这种先进工艺制备的新型触头材料具有良好的性能.     

Flattening behavior of copper droplets in plasma spray forming

A two-dimensional axisymmetric model, with 8700 and 7500 quadrilateral elements for the fluid and substrate zone separately, was developed to simulate the impacting and flattening process. The volume of fluid technique was employed to track the interface between the air and droplet. The relationships between the droplet pre-impact parameters and the flattening time as well as the flattening ratio were investigated by altering one of the parameters while remaining the others unchanged. The results show that the droplet height reaches its minimum value at approximately half of the spreading time, which also indicates the finish of vertical fluid flow at that time. The flattening ratio increases with the increase of the three pre-impact parameters-droplet diameter, temperature and velocity, even though the flattening time decreases when the droplet velocity increase.     

Thermal spray shape deposition

This paper describes a new spray-forming process based on thermal spray shape deposition. Shape deposition processes build three-dimensional shapes by incremental material buildup of thin, planar crosssectional layers. These processes do not require preformed mandrels and can directly build three-dimensional structures of arbitrary geometric complexity. The basis for the thermal spray approach is to spray each layer using a disposable mask that has the shape of the current cross section. Masks can be produced from paper rolls, for example, with a CO₂ laser. In addition to applications for rapid prototyping, this approach makes possible the fabrication of composite structures and integrated electronic/mechanical assemblies that are not feasible with conventional manufacturing technologies.     

Numerical simulation of splat formation dynamics in plasma spray forming

Plasma spray forming shows overwhelming advantages in rapid fabricating parts and moulds. The coating microstructure is strongly dependent on the splat morphology and inter-splat contact nature. Therefore, it is necessary to investigate the splat formation mechanism in order to analyze the coating properties. A dynamical process of a single fully molten droplet impacting onto a smooth surface was investigated. At the same time, the interaction between the two molten droplets in the horizontal and vertical directions was also simulated. Finally, the simulations of impact of a molten droplet on an inclined plane and a sharp edge were presented. It is concluded that the relative distance of the two droplets strongly influences the dynamics of the two droplets interaction. The various surface conditions have direct effects on the dynamics of splat formation. When a droplet impacts onto an inclined surface and a sharp edge, the splat morphology changes obviously and the phenomenon of break up is observed.     

等离子体喷涂纳米结构热障涂层微观组织及性能

以纳米结构氧化钇部分稳定的氧化锆热喷涂粉末为原料,采用大气热等离子体喷涂法制备了纳米结构热障涂层。利用扫描电子显微镜和X射线衍射仪对粉末原料及涂层的微观组织和结构进行分析,并对涂层的结合强度及热导率进行测定。结果表明,纳米结构热障涂层具有优异的性能,热导率为1.1 W/(m.K),界面结合强度为47 MPa。并分析了涂层纳米结构组织对涂层性能的影响,明确了优化涂层微观组织结构和提高涂层性能的具体方法。     

喷射成形6061铝合金的热处理工艺

对喷射成形6061铝合金的热处理工艺进行研究,采用硬度测试、拉伸试验和透射电镜等研究固溶温度、时效温度和时效保温时间对合金显微组织和力学性能的影响规律。结果表明:随固溶温度的升高,合金硬度也随之升高,而其抗拉强度、屈服强度和断后伸长率则先增大后减小;合金硬度、抗拉强度和屈服强度随时效温度的升高先增大后减小,断后伸长率却一直减小;合金硬度、抗拉强度和屈服强度曲线随时效温保温时间的延长呈驼峰状变化,断后伸长率则变化不大,只在17 h时有所增大;喷射成形6061铝合金的最佳热处理工艺为530℃固溶1 h+175℃时效8 h。     

Spray forming technology for military applications

Over the past five years, the Annapolis Detachment, Carderock Division, Naval Surface Warfare Center (formerly David Taylor Research Center) has established a state- of- the- art spray forming facility for the study and exploitation of this near net shape manufacturing process. Spray forming is a single step gas atomization/deposition process which yields ferrous and nonferrous, near final shape, near fully dense preforms that has proven to be a viable and cost effective alternative to conventional metalworking technology for the production of material preforms with properties surpassing those of their cast and wrought counterparts. Current programs at Carderock Divison Naval Surface Warfare Center are aimed at optimization of the process, certification of the spray formed products and industrialization of the technology.     

Porosity and surface roughness simulation of nickel-aluminum coating in plasma spray forming

As the important evaluation parameters concerning the spray qualities, the porosity and surface roughness of the coatings obtained by thermal spray forming have great influence on their forming accuracy, mechanical properties and service lifetime. But it is difficult to predict or control the two parameters for such a highly nonlinear process. A two-dimensional simulation of coating porosity and surface roughness of nickel-aluminum alloy （Ni-5%Al） in plasma spray forming was presented, which was based on the multi-dimensional statistical behaviors of the droplets as well as the simplification and digitization of the typical splat cross sections. Further analysis involving the influence of the droplet diameters and the scanning velocities of the spray gun on the two parameters was conducted. The simulation and analysis results indicate that the porosity and surface roughness are more influenced by the droplet diameters, but less influenced by the spray gun velocities. The results will provide basis for the prediction or control of coating mechanical properties by depositing parameters.     

喷射成形Al-Zn-Mg-Cu合金挤压态的组织和力学性能

研究了利用喷射成形辅以挤压制备Al-5.72Zn-2.36Mg-1.66Cu合金后优化的组织结构特征和力学性能。结果表明,合金基体组织均匀细化,晶粒形貌趋于圆整,平均晶粒大小达到10 μm左右。当合金的冷却条件通过快速凝固技术改变时,会产生不同程度的固溶强化效果和第二相弥散强化效果,从而改善了合金的整体性能。合金的屈服强度和抗拉强度分别平均提高了20%左右,且伸长率也略有提高。     

喷射成形Al—Zn—Mg—Cu系高强铝合金的组织与性能

利用喷射成形工艺制备了Al-Zn-Mg-Cu系高强铝合金材料,研究了热挤压工艺与热处理工艺对材料微观组织与力学性能的影响,在峰时效的情况下材料表现出了高的力学性能指标,抗拉强度达到754MPa,屈服强度达到722ＭＰa,断裂延伸率达到8%,与采用传统铸造变形工艺制备的同类合金相比（σb≥610MPa,σ0.2≥580MPa,δ≥4%),性能有了明显的提高。合金性能的提高与其基体中呈弥散分布的Mg7Zn3相有很大的关系,合金的主要强化机制是沉淀强化。     

Formation of unidirectional nanoporous structures in thickly anodized aluminum oxide layer

A series of anodic aluminum oxide(AAO) was grown on the commercially pure 1050 aluminum sheet by controlling electrolyte temperature (2–15 °C) and an odizing time (0.5–6 h), using a fixed applied current density of 3 A/dm² in diluted sulfuric acid electrolyte. A crack-free thick AAO with the thickness of 105–120 μm and containing unidirectional nano sized pores (average pore diameter of 5–7 nm) is successfully achieved in the specimens anodized for 2 h, irrespective of electrolyte temperature. When anodizing time reaches 6 h, very thick AAO with the thickness of 230–284 μm is grown, and average diameter of unidirectional pores is in the range of 6–24 nm. The higher values in both the AAO thickness and pore diameter are attained for the specimens anodized at higher temperatures of 10–15 °C. A crack is observed to exist in the AAO after anodizing up to 4 h and more. A higher fraction (more than 9%) of the crack is shown in the specimens anodized at higher temperatures of 10–15 °C for 6 h and a considerable amount of giant cracks are contained.     

Thixoforming of 6066 aluminum alloy by multi-layer spray deposition

1　ＩＮＴＲＯＤＵＣＴＩＯＮ1.1　ＴｈｉｘｏｆｏｒｍｉｎｇＩｎｔｈｅｅａｒｌｙ 1970ｓ ,ａｓｐｅｃｉａｌｔｈｉｘｏｔｒｏｐｉｃｍｉ ｃｒｏｓｔｒｕｃｔｕｒｅｉｎｓｅｍｉｓｏｌｉｄｓｔａｔｅｗａｓｄｉｓｃｏｖｅｒｅｄｗｈｅｎＦｌｅｍｉｎｇｓａｎｄｈｉｓｃｏ ｗｏｒｋｅｒｓｓｔｕｄｉｅｄｔｈｅ“ｈｏｔｔｅａｒｓ”ｏｆｔｈｅｃａｓｔｉｎｇａｌｌｏｙｓ[1] .Ｔｈｅａｐｐａｒｅｎｔｖｉｓｃｏｓｉｔｙｏｆｔｈｅｓｅｍｉｓｏｌｉｄｍａｔｅｒｉａｌｓｄｅｃｌｉｎｅｓｓｈａｒｐｌｙｗｉｔｈｔｈｅｉｎｃｒｅａｓｅｏｆｔｈ…     

Near-net-shape forming of metallic bipolar plates for planar solid oxide fuel cells by induction plasma spraying

In one of the present designs of solid oxide fuel cells (SOFC), metallic bipolar plates with gas channels on the surface are used, which consist of a chromium alloy and are manufactured by a time consuming and costly multistep process. To reduce the production time and costs, attempts were made to develop an alternative near-net-shape production method based on RF-induction plasma spray technology. With this process raw powders, as applied for the “conventional” sintering route as well as recycled powders from used bipolar plates, have been applied. The process parameters were adapted to both powders, and the obtained products were qualified. The near-net-shape production requires the formation of a gas channel structure already with the spray process using structured substrates. Therefore, different spray angles occur during the deposition process. The influence of the spray angle on the microstructure of the free-standing parts was investigated. The required gas tightness for grooved profiles with relatively large channel depths and widths can only be achieved using spray angles between 90° and approximately 60°. Then a tilting of the substrate and an adapted design of the gas channel profiles are needed to fulfill the structural requirements for the bipolar plates.     

Production of high strength Al-Zn-Mg-Cu alloys by spray forming process

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｌ Ｚｎ ( 7×××ｓｅｒｉｅｓ)ａｌｌｏｙｓｈａｖｅｂｅｅｎｗｉｄｅｌｙｕｓｅｄｂｅｃａｕｓｅｏｆｈｉｇｈｓｔｒｅｎｇｔｈ ,ｃｏｒｒｏｓｉｏｎ ｒｅｓｉｓｔａｎｃｅａｎｄｏｔｈｅｒｇｏｏｄｐｒｏｐｅｒｔｉｅｓ[1 ,2 ] .Ｂｕｔａｐｒａｃｔｉｃａｌｃｏｎｔｅｎｔｌｉｍｉｔｏｆ7%Ｚｎ (ａｌｌｏｙｓ 70 75,71 75ａｎｄ 7475ｅｔｃ)ｉｓｉｍｐｏｓｅｄｆｏｒｃｏｎｖｅｎｔｉｏｎａｌｃａｓｔｍａｔｅｒｉａｌｓｂｅｃａｕｓｅｏｆｓｏ ｌｕｔｅｍａｃｒｏ ｓｅｇｒｅｇａｔｉｏｎａｎｄｃｏａｒ…     

喷射成形7055铝合金的显微组织和力学性能

采用全自动控制往复喷射成形工艺制备了7055铝合金的大规格喷射成形锭坯.通过显微组织分析和力学性能测试,研究工业规格喷射成形7055铝合金的初始组织、挤压工艺及热处理制度对显微组织和力学性能的影响.结果表明,喷射成形7055铝合金锭坯规格可达d 260 mm×1600 mm,晶粒为等轴状,粒度宏观均匀,主要在20～30 μm,组织无明显宏观偏析,锭坯致密度达到98.2 %.喷射成形态材料的T6态σb为500～543 MPa,显示控制往复喷射成形铝合金锭坯冶金质量优越.喷射成形锭坯经过小挤压比变形后达到全致密,大规格产品的T6态纵向σb提高到745 MPa,δ为12.8 %.     

新型60Si40Al合金封装材料的喷射成形制备

利用喷射成形技术制备了60Si40Al合金新型电子封装材料.研究了各工艺参数对沉积坯件的影响,确定了较佳工艺参数.研究了材料的显微组织以及沉积态合金在加热保温过程中的组织转变规律,确定了热等静压温度,进行了热等静压致密化处理.研究结果表明:材料显微组织细小,一次硅相尺寸约为10μm,且均匀弥散分布,该材料的热膨胀系数为9×10-6～10×10-6/K,热导率约为110W/(m*K),是一种理想的电子封装材料.     

Effect of additional elements on aging behavior of Al-Zn-Mg-Cu alloys by spray forming

1 Introduction Spray atomization and deposition technology, also termed spray forming, has attracted considerable attention because of its excellent potential advantages in the production of structure materials: cost-effectiveness in combination with pro…