变质处理对新型 Al-10Sn-4Si 合金结晶组织的影响

采用钠盐变质剂对新型Ａｌ－１０Ｓｎ－４Ｓｉ轴承合金熔体进行变质处理,结果发现：变质处理不仅可以细化共晶Ｓｉ相,而且可以明显地改善共晶β（Ｓｎ）相的结晶行为,使得β（Ｓｎ）相环绕Ｓｉ粒子凝固并且以近似网状分布于晶界,为均匀化后形成均匀的β（Ｓｎ）包Ｓｉ的“包晶”式相组织创造了有利的条件。     

不同凝固条件对镍铬合金组织性能的影响

在自制的多功能高梯度定向凝固及电弧熔炼设备上,控制6J20镍铬合金的凝固速度,制备出铸态力学性能试棒和金相试样,观察6J20镍铬合金材料的光学显微组织并测试其力学性能.结果表明,镍铬合金凝固速度越大,其断裂强度越高,延伸率则有较大的降低;凝固速度很大时,镍铬合金显微组织为细小的树枝晶的单相固溶体;凝固速度较小时,镍铬合金的显微组织为均匀分布的十字花瓣形或近似于圆形的单相固溶体.断口分析表明,快速凝固镍铬合金试样的断口具有沿晶断裂和穿晶断裂的特征;定向凝固镍铬合金试样的断口特征具有穿晶断裂的特征.     

凝固速度对高铬铸铁共晶组织的影响

采用液态金属冷却的定向凝固技术,获得了在不同凝固速度下的高铬铸铁(Fe-3.35C-27.5Cr),并研究了凝固速度对高铬铸铁共晶组织的影响规律.结果表明,当温度梯度为150K/cm,凝固速度为1~10μm/s时,固液界面均可维持平直状,可获得M7C3型碳化物呈定向排列的高铬铸铁,碳化物与基体结合牢固,具有原位生长复合材料的效果.     

冷却速度对SiCp/2024Al热残余应力影响的数值模拟

针对冷却速度对SiCp／2024Al复合材料热残余应力的影响，通过复合材料显微组织观察，根据复合材料的形貌特征，建立了平面应力状态的复合材料组织模型，利用有限元方法对SiCp／2024Al复合材料淬火和退火过程的热应力进行了数值模拟．结果表明，由于SiC增强颗粒与铝基体之间的热膨胀系数差异较大，热处理后颗粒和基体的界面附近产生很大的热残余应力场，同时基体发生塑性应变；冷却速度对复合材料热残余应力没有明显影响．     

原始组织形态和冷却速度对T91钢组织的影响

采用箱式电阻炉对T91钢进行冷却实验,研究T91钢连铸坯和轧制坯冷却过程中原始组织形态和冷却速度对其相变组织和临界冷却速度的影响。结果显示:T91钢坯冷却过程中只有铁素体和马氏体转变,并且原始组织状态对临界冷却速度的影响不同,细小均匀的组织将增大临界冷却速度;T91钢连铸坯连续冷却过程中,当冷却速度在8℃/min以上时全部为马氏体组织,冷却速度为3~7℃/min时为铁素体和马氏体混合组织,冷却速度在2℃/min以下时几乎是铁素体组织;T91钢轧制坯连续冷却过程中,冷却速度在10℃/min以上时组织全部为马氏体,冷却速度为4~9℃/min时为铁素体和马氏体混合组织,冷却速度在3℃/min以下时组织几乎为铁素体。     

Effect of Mg on Microstructure and Growth Kinetics of Zn-22.3Al-1.1Si Coating

The effects of Mg on the microstructure and growth kinetics of the hot-dip Zn-22.3 Al-1.1 Si-x Mg(x = 0, 0.2, 0.4, and 0.6) coatings were investigated in detail. Scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction studies revealed the presence of η-Zn, α-Al, Zn/Al eutectoid,(Si), Al/Si eutectic, and Zn/Al/Mg_2 Zn11 ternary eutectic on the top surface of these Mg-containing coatings. Especially, a small amount of MgZn2 phase appears in top surface of Zn-22.3 Al-1.1 Si-0.6 Mg coating. Five phases are found in the alloy layers, i e, Fe_2 Al_5, FeAl_3, τ_(5C), τ_(5H), and τ_1. The addition of 0.2% Mg can delay the emergence of FeAl_3 phase. When the Mg content is more than 0.2%, the outer layers of coating change from τ_(5C) to τ_(5H) phase. The growth of the inhibition layer is diffusion controlled for various Mg content baths. Mg improves the corrosion resistance of the Mg-containing coatings, and the Zn-22.3 Al-1.1 Si-0.6 Mg coating possesses the highest protective properties.     

Cu对Al-15Si合金的高温摩擦磨损行为的影响

研究了Al-15Si-xCu合金高温(400℃)摩擦磨损行为.采用Pandat软件计算了Al-15Si-xCu系合金平衡相图.利用光学显微镜和扫描电镜研究了Al-15Si-xCu系活塞合金不同铜含量下400℃摩擦磨损行为.研究结果表明:活塞合金经T6热处理后,随着Cu含量的增加,摩擦因数逐渐减小,磨损失重量减少,其高温耐磨性能得到明显提高;w(Cu)含量为4.5和5.5时,活塞合金的摩擦磨损性能差异较小,这与合金中高温稳定相(Q相、ε相、θ相)密切相关;w(Cu)含量为2.5和3.5的活塞合金,其磨损机制主要是粘着磨损,而对于w(Cu)含量为4.5和5.5的合金,其磨损机制主要是磨粒磨损.     

电子束表面超快速熔凝冷却速率对形成非晶层的影响

为探索制备大面积表面非晶层的新途径，采用电子束表面超快速熔凝处理的方法，通过显微硬度、金相组枳和Ｘ射线衍射及透射电镜分析，研究了电子束表面超快速熔凝冷却速率对形成非晶层的影响。结果表明，电子束与基体的交互作用时间愈短，加热和冷却速率愈大。随冷却速率增大凝固组织细化，熔凝层显微硬度增大。当冷却速率为３．３４×１０７℃／ｓ时，即可获得可检测的非晶层。为一般结构材料的表面直接转变为非晶层开辟了新途径。     

凝固偏析对氧化铝/铝-铜合金复合材料性能的影响

利用挤压铸造技术制备氧化铝／铝-铜合金复合材料，研究了凝固偏析对复合材料机械性能的影响．结果表明：复合材料在凝固过程中由于选择结晶，基体中的溶质元素偏聚在纤维／基体界面或晶界上；纤维加速了复合材料的时效强化过程，随着纤维体积分数的增加，复合材料的硬度、强度、弹性模量增大，而塑性下降；随着预制件预热温度的升高，冷却速度减慢，凝固偏析加剧，复合材料的机械性能下降．     

Al-0.6Mg-0.6Si铝合金MIG焊接接头显微组织与微区成分研究

对轨道车辆用新型Al-0.6Mg-0.6Si铝合金进行了熔化极隋性气体保护(MIG)焊接,利用光学金相(OM)、能谱(EDAX)分析等测试手段,对焊接接头的显微组织与微区成分(质量分数)进行 了分析.结果表明:采用MIG焊接方法能够获得成形良好的接头,焊缝中心结晶形成典型铸态组织,但易于偏聚形成显微夹杂,靠近熔合线的焊缝逐渐由焊缝边缘的柱状晶过渡到枝状晶.熔合线附近的焊缝边缘易于形成Si偏析带,A1-0.6Mg -0.6Si基体组织的质量比m(Mg):m(Si)≈1.04:1,焊缝中心Mg元素受电孤高温烧损,Mg含量(质量分数)为3.08％.     

Ni_（78.6）Si_（21.4）合金的深过冷与凝固组织演化

深过冷技术研究是凝固科学中重要的研究领域之一.文中采用玻璃熔融净化与循环过热法使Ni78.6Si21.4合金获得了318K的过冷度,研究了其凝固组织随初始过冷度（ΔT）的演化规律,并对凝固组织中的亚稳相进行了分析.研究发现：当ΔT〈193K时,凝固组织为Ni3Si＋（Ni3Si＋α-Ni）非规则共晶;193K〈ΔT〈250K,凝固组织为α？Ni＋（Ni3Si＋α-Ni）非规则共晶;ΔT〉250K时,凝固组织为完全的非规则共晶;随过冷度的增加,过冷合金熔体中依次出现了亚稳相Ni31Si12相和Ni3Si2相.     

Effect of Silver Element on Microstructure and Properties of W-30Cu/TiC Composites

W-30 wt%Cu and TiC-50 wt%Ag were successfully synthesized by a novel simplified pretreatment followed by electroless plating. The 0 wt% TiC, 0.5 wt% TiC, and 0.5 wt%TiC-0.5 wt%Ag composite powders were added to W-30 wt%Cu composite powders by blending, and then reduced. The reduced W-30 Cu, W-30 Cu/0.5 TiC, and W-30 Cu-0.5 Ag/0.5 TiC composite powders were then compacted and sintered at 1 300 ℃ in protective hydrogen for 60 min. The phase and morphology of the composite powders and materials were analyzed using X-ray diffraction and field emission scanning electron microscopy. The relative density, electrical conductivity, and hardness of the sintered samples were examined. Results showed that W-30 Cu and TiC-Ag composite powders with uniform structure were obtained using simplified pretreatment followed by electroless plating. The addition of TiC particles can significantly increase the compressive strength and hardness of the W-30 Cu composite material but decrease the electrical conductivity. Next, 0.5 wt% Ag was added to prepare W-30 Cu-0.5 Ag/TiC composites with excellent electrical conductivity. The electrical conductivity of these composites(61.2%) is higher than that in the national standard(the imaginary line denotes electrical conductivity of GB IACS 42%) of 45.7%.     

Effect of Hot-Plate Rolling on the Microstructure Evolution and Mechanical Properties of In-Situ Nano-TiCP/Al-Mg-Si Composites

The hot-plate rolling (HPR) process is adopted to achieve the optimal strength-ductility for the in-situ nano-TiC_P/Al-Mg-Si composites.There was no crack in the sheet by single pass of hot-plate rolling with a thickness reduction of 80%,while there were numerous cracks in the sheet by two passes of conventional hot rolling to achieve a total reduction of 50%.The microstructure and mechanical properties of the composites subjected to 80% thickness reduction of hot rolling at 540 ℃ were...     

变燃速发射药微观结构及对燃烧的影响

对双层结陶变燃速发射药微观结构进行了研究,讨论了银纹的存在及其特征性,提出了银纹的作用机理．通过扫描电镜,可以观察到银纹厚度随温度的变化;通过密闭爆发器试验,对经高低温处理后的发射药燃烧性能和原样的燃烧性能进行比较;在某口径火炮上进行内弹道试验,分析其高温、低温、常温内弹道性能．通过银纹厚度随温度的变化,调整发射药的燃烧面积,使变燃速发射药具有所希望的能量释放规律．实验结果表明了银纹原理的正确性、银纹的稳定性及银纹的存在使双层结构变燃速发射药具有明显的低温度系数．     

熔体过热处理影响合金凝固特性的机制

对熔体过热处理影响合金液形核温度、结晶潜热和结晶相生长特性的机制进行了理论研究.从理论上得到了铝熔体中最大尺寸原子团的原子数与熔体温度、合金结晶潜热和合金中结晶相生长特性因子与合金液性质之间的理论关系式,根据得到的理论关系式可预测熔体过热温度对金属液的形核温度、合金液的结晶潜热及合金中结晶相生长特性因子影响趋势.由文中理论关系预测出Al-Si合金的形核过冷度随熔体过热温度的升高而增大、结晶潜热随熔体过热温度的升高而减小、结晶相生长特性因子随熔体过热温度的升高而减小.     

Microstructure and Thermal-protective Property of CPED Coating with ZrO_2 Nanoparticles Addition on Al-12Si Alloy

A novel thermal-protective coating has been successfully prepared by CPED process on a cast Al-12%Si alloy with the addition of ZrO_2 nano-particles in the electrolyte. The microstructures and phase composition of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. With ZrO_2 nanoparticles addition, the cathode plasma discharge on the coating surface is more obvious than that without ZrO_2 nanoparticles addition, the coating is more uniform and compact, and the thickness of the coating increases. Furthermore, the content of Zr and Y elements increases and the degree of crystallization of the coating is more complete. The formation of the solid solution of yttrium stabilized zirconia is promoted by cathode plasma discharge. In addition, the thermal insulation temperature increases as ZrO_2 nano-particles are added to the electrolyte. After 1 000 cycles of thermal shock, there was no cracking in the coating surface layer, which indicated that the CPED coating with ZrO_2 nanoparticles addition possessed a good thermal shock resistance.     

增强剂对碳／碳材料沉积速率影响的实验研究

从实验探索了增强剂对碳／碳复合材料沉积速率的影响，提出了提高沉积速率的方法。实验结果表明：采用经过石墨化处理和表面改性处理的碳布作为增强剂，所制得的坯体沉积速率快，样品最终密度高；碳纤维体积含量（为３０％～４５％时）对样品最终密度无明显影响。     

Mg-6Al-xNd(x=2,4)合金的组织结构与凝固行为

Nd添加到Mg-6Al合金后,析出针状的Al11Nd3和多边形状的Al2Nd,前者主要分布于枝晶界或晶界,后者主要分布于晶粒内.两相含量均随Nd含量增加而增加,其中前者含量明显高于后者.含Nd合金的凝固过程经历Al2Nd析出、α-Mg析出、Al11Nd3+α-Mg同时析出等过程.合金热裂倾向随着Nd含量的增加而升高,这是由于Al11Nd3和Al2Nd析出温度高,导致合金凝固区间收缩和共晶相对量减少,降低了剩余液相的流动性;枝晶界或晶界上的针状Al11Nd3相增加了合金凝固后期流动补缩的难度;Al11Nd3相和α-Mg凝固收缩率不同,易导致两者界面上产生较高的热应力.     

Effect of Cooling Rate on Morphology and Oxygen Permeability of Polypropylene

The influence of different cooling rates on the morphology and oxygen permeabilityr of polypropylene containing ferrocene has been investigated. The spherulitic crystalline size and structure, which can affect the oxygen permeability are dependent upon the heating temperature, annealing time and cooling rate. The modulus of the composite was measured b}' dynamic mechanical analysis.     

熔体过热处理对亚共晶Al—Si合金凝固特性和组织的影响

研究了熔体过热处理对Al-11%Si合金形核温度、结晶潜热和凝固组织的影响规律.实验结果发现合金的形核温度先随过热温度的升高而降低;过热温度超过860℃后,过热温度对形核温度没有明显影响.合金的结晶潜热随过热温度的升高具有先减小后增大的规律,过热温度为860℃时,结晶潜热达到其最小值.过热温度过低和过高时,共晶硅均为粗大的针片状,表现出小平面生长的特征;过热温度为860℃时,共晶硅为细小的点状,表现出非小平面生长的一些特征.