液相烧结钨合金断裂与界面偏聚的研究

磷是W-Ni-Fe系液相烧结钨合金中脆化界面的主要元素,它在各界面上的偏聚浓度是很不均匀的,以钨颗粒-粘结相界面上靠近钨颗粒一侧浓度最高。快冷可以明显抑制磷的界面偏聚,从而提高界面结合强度。氧、钾、硫可以在合金中形成零散分布的极高浓度富集区,其脆化作用不可忽视。     

稀土含量对高密度钨合金性能的影响

通过粉末冶金法制备了添加稀土元素La，Ce的93W-4．9Ni-2．1Fe合金，研究不同稀土元素及不同稀土含量对高密度93钨合金静、动态力学性能的影响规律。结果表明：由于稀土元素La，Ce的加入，减少了杂质元素氧在钨-粘结相界面的偏析，减小了钨颗粒的连接度，从而改善了钨合金的力学性能，尤其是合金的动态力学性能得到显著提高，稀土元素的合理添加量为0．10％～0．15％。     

添加镧对W—Mo—Ni—Fe重合金的影响

为改善W－Mo-Ni-Fe重合金机械性能，本文研究了添加稀土元素La对重合金及其作用机理的影响。结果表明添加适量的La可明显改善这种合金的机械性能。扫描电子显微术、透射电子显微术、X光衍射图和俄歇电子光谱法试验结果机械性能的改善主要是由于形成稳定的LaMnO3和少量Mn3O4，改变了杂质元素氧存在形式和分布状态，减少了氧界面偏析，从而增强W－基体界面的粘结强度。因此，合金的机械性能得到改善。     

高温复压对93W-4.5Ni-2.5Fe合金磷偏析的影响SCIEI

用Auger谱仪、电子探针分析和透射电镜、扫描电镜观察等手段,考察了高温复压处理对93钨合金磷偏析的影响。发现在1200—1500℃保温后炉冷,在钨-钨晶界特别是钨-粘结相相界上存在磷偏析,而在该温度范围复压后炉冷,则未发现磷在晶界和相界上偏析;复压处理态材料粘结相中位错直接影响磷向界面偏析,为退火处理的材料因磷在界面偏析而引起机械性能下降。     

杂质对钨晶界脆性的影响

一、引言许多文献报导,杂质的存在,特别是磷、钾、碳和氧的存在,对钨的力学性能有很大的影响。这些杂质在晶界处偏析,造成晶间脆性。本研究的宗旨是探讨杂质对各种不同钨     

高钨高比重合金结构的局限性

高比重合金对于实用来说,有密度和机械性能兼优的特点。本文着重研究含钨量为90-99.5%(重量)高比重合金的密度、强度和韧性的变化。研究了性能、工艺和显微结构与钨含量之间的基本关系。当钨含量高时,由于接触性增加,强度和延性降低。断裂观察证明,性能的限度与高接触性有关。高钨高比重合金易受到杂质在钨-基体相界面偏析的影响。因此,高钨高比重合金的机械性能对工艺条件是很敏感的。含钨量一定时,接触性是由二面角确定的。而且,界面的数量随晶粒的尺寸而变化。因此,这两种显微结构的特点与控制机械性能的杂质偏析有关。在本文中指出,对钨含量高达98%(重量)的高钨高比重合金,其强度为850兆帕,延伸率为12%。通过添加微量的合金化元素改变二面角和钨-基体相界面性能而获得更高的性能是完全可能的。     

高温合金中钛铌钨和钼的某些晶界析出行为

采用晶粒表面的萃取碳复型技术，观察研究了钛在一种具有大晶粒尺寸的高温合金中的晶界析出行为－晶界（Ti,Mo）C脆性包膜的形成和效应；不同含量的铌对一种高温合金晶界析出相类型、形貌分布、成分和数量的影响；分析讨论了钨和钼等元素对某些高温合金晶界碳化物和硼化物的析出行为存在的直接作用和间接作用。     

7B04合金的断裂韧性

研究了Fe和Si杂质元素和Cu元素含量、合金中氢含量和钠离子含量、晶粒细化以及铸锭高温均匀化处理对7B04合金断裂韧性的影响。降低Fe和Si杂质元素及调整合金主要成分Cu含量，可以减少难溶粗大硬相质点和过剩相；降低合金氢含量和钠离子含量可以降低氢脆和钠脆；加强晶粒细化可以获得细小晶粒组织；进行高温均匀化处理促使粗大第二相质点溶入基体。这些措施使合金获得高纯化、高纯净化、高均匀化和非常细小的晶粒，从而使合金的断裂韧性得到较大提高。     

W-Ni-Fe合金微观组织与冲击性能研究

在不同混料时间相同烧结工艺下制备了两件钨合金。采用金相显微镜、扫描电子显微镜以及能谱技术对两件钨合金的微观组织以及成分进行了表征,并对其进行了冲击性能测试。微观组织观察表明两件钨合金晶粒形貌、尺寸差别不大,钨颗粒晶粒尺寸介于10⁵0μm。微区成分测试表明两件样品钨颗粒微区成分基本相同,而粘结相区差别较大。混料时间较长的钨合金粘结相区W元素含量较高,Ni、Fe、Co元素含量较低;而混料时间较短的钨合金微区成分正好相反。冲击韧性测试表明混料时间较长的钨合金冲击韧性明显降低。冲击断口显示混料时间较长的钨合金粘结相区撕裂棱较短,而混料时间较短的钨合金粘结相区撕裂棱较长。     

铸态稀土铝合金中元素分布与枝晶偏析

本文研究了稀土对铝合金中不同合金元素的分布和枝晶偏析的影响。研究表明，当合金中稀土加入量较少时，合金中的稀土没有富集现象；当加入量较多时，合金中的稀土主要与合金元素作用形成化合物。稀土的加入增加了与工业纯铝中杂质元素、Ａ１－Ｃｕ和Ａ１－Ｃｕ－Ｌｉ合金中Ｃｕ等元素形成化合物的趋势和能力，增大了这类元素的枝晶偏析；减少了Ａ１－Ｚｎ－Ｍｇ合金基体中Ｚｎ、Ｍｇ等合金元素形成化合物的趋势和能力，而对其枝晶偏     

Effect of carbon content and cooling mode on the microstructure and properties of Ti(C,N)-based cermets

Ti(C,N)-based cermets were prepared by vacuum liquid sintering. The effects of carbon content as well as cooling mode on the microstructure, magnetic and mechanical properties of the cermets were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). Hardness and transverse rupture strength (TRS) were also measured. The grains of Ti(C,N)-based cermets became finer and solid solubility of titanium, molybdenum, tungsten in binder phases decreased with increasing carbon content. The thickness of the rim phases increased when the cermet was annealed at 1360 °C for 30 min during cooling, which resulted in the decrease of the hardness and the transverse rupture strength (TRS). On the other hand, the magnetic saturation of Ti(C,N)-based cermets increased with increasing carbon content, which was due to the decrease of the solid solution of alloy elements in binder phases.     

Effect of bonding temperature and heat treatment on microstructure and mechanical property of Mg−6Gd−3Y alloy vacuum diffusion bonded joints

Diffusion bonding of as-cast Mg?6Gd?3Y magnesium alloy was carried out at temperatures of 400?480 °C with bonding pressure of 6 MPa for 90 min. Diffusion bonded joints were solution treated at 495 °C for 14 h and then aged at 200 °C for 30 h. Microstructures and mechanical properties of joints were analyzed. The results showed that rare earth elements and their compounds gathering at bonding interface hindered the grain boundary migration crossing bonding interface. Tensile strength of as-bonded and as-solution treated joints increased firstly and then decreased with the bonding temperature increasing due to the combined effects of grain coarsening and solid-solution strengthening. As-bonded and solution-treated joints fractured at matrix except the joint bonded at 400 °C, while aged joints fractured at bonding interface. The highest ultimate tensile strength of 279 MPa with elongation of 2.8% was found in joint bonded at 440 °C with solution treatment followed by aging treatment.     

粉末粒度对液膜溶解扩散连接特性的影响

以铜基合金粉末为焊材，对ZCuBe2．5合金进行了液膜溶解扩散连接。用铜基合金粉材所获得的焊缝组织由均匀细小的a-Cu等轴晶和晶间金属间化合物组成。界面母材仍保持其原始粗大的a-Cu树技晶和晶间γ包晶相组织形貌。焊缝与母材结合良好．通过原子互扩散形成了厚度约130～160um，的过渡固溶体结合界面。随着粉末粒度的减小，焊缝中等轴晶尺寸逐渐减小，焊缝组织得到明显的细化；形成的扩散过渡层厚窿减小，组织更加致密，接头抗拉强度增大；热影响区变窄，硬度分布更趋合理。扩散连接过程中温度梯度的存在可使液膜溶解扩散焊在很短的时间内实现高强度连接。     

稀土银合金显微组织观察与分析

对稀土银合金材料进行了金相观察和电子探针扫描分析以及显微硬度测定。实验结果表明,添加两种性质差交大的稀土元素可以充分发挥互补作用,改善银合金的组织与性能。含有稀土钇的银合金有较强的加工硬化效果和较好的抗高温氧化作用。稀土钇与轻稀土元素组合添加将有助于改善银合金的综合性能。     

钨合金的形变强化新工艺与断裂机制研究

形变强化是提高钨合金性能的必要手段,是制备拉伸强度大于1200MPa的钨合金穿甲弹弹芯材料的主要途径。形变强化主要通过旋锻、静液挤压、热挤压或其它热机械加工复合变形技术实现。形变强化的机制主要是大变形使钨晶粒呈纤维状。本文综述了国内外对钨合金穿甲弹弹芯材料的形变强化工艺和机制的研究现状。     

Microstructural and Mechanical Properties of Hot Roll Bonded Titanium Alloy/Low Carbon Steel Plate

In this paper, a titanium alloy and low carbon steel were bonded via hot rolling in a vacuum, and the effect of roll bonding temperature and reduction ratio on the microstructural and mechanical properties of the plate was studied. When the bonding temperature was between 850 and 1050 °C, the shear strength of the interface increased with an increasing reduction ratio from 18 to 70%. At a bonding temperature of 950 °C and at a rolling reduction ratio of 70%, the best bonding strength was obtained, and a shear fracture occurred on the low carbon steel matrix. At 1050 °C, brittle compounds, i.e., TiC, FeTi, and Fe₂Ti, formed at the interface, which decreased the bonding strength. The large reduction ratio can break up compounds at the interface and extrude fresh metal for bonding, thereby increasing the bonding strength.     

Microstructural Factors That Decrease the Local Strength of Grain Boundaries in Martensitic Steels

As a result of the phase transformation of austenite to martensite during steel quenching, weakened structural regions, specifically the boundaries of the original austenite grains, have been formed. They are weakened because of microstructural factors, such as the residual internal microstrains and segregation of embrittling impurities. The joint effect of microstructural factors, namely, residual microstrains and segregation of phosphorus and carbon at grain boundaries, on reducing the local strength of the boundaries of the initial austenite grains in martensitic steels is quantitatively evaluated, and the impacts of these microstructural factors have been separated. The dependences of the local grain-boundary strength on the ratio of various levels of residual microstrains and on the atomic concentration of phosphorus impurities at the grain boundary in segregation spots have been determined. It has been shown quantitatively that the adsorption enrichment of the austenite grain boundaries with phosphorus leads to a decrease in the intergrain adhesion and facilitates the emergence and development of cracks along the boundaries of the initial austenite grains. The quantitative dependence of the local strength of grain boundaries on the concentration ratio of carbon and phosphorus in them has been shown. Carbon in concentrations of up to 0.04% reduces the embrittlement of the boundaries due to the segregation of phosphorus and loses its neutralizing effect on the phosphorus segregation at concentrations of more than 0.04%, so the phosphorus concentration at the grain boundaries increases and the embrittlement resistance of the latter decreases. The applicability of the developed technique for the quantitative evaluation of the local strength of hardened steel grain boundaries by using tests on delayed fracture and applying the method of finite elements to determine the local strains has been shown.     

稀土元素对高强高导铝合金的性能影响

通过在纯铝中添加混合稀土（La和Ce）,研究稀土元素对高强高导铝合金性能的影响和作用机理。按照国家标准测试了试验样品的电阻率和拉伸强度,利用扫描电镜观察了样品的显微组织和化合物的分布,并用能谱对这些化合物进行分析,最后用材料科学基础和金属电子论分别解释了混合稀土对铝合金强度和电阻率的作用。结果表明：混合稀土可以净化晶粒和细化晶粒;加入0.1%~0.4%（质量）混合稀土可以在电阻率增高不大的情况下大幅提高其强度;在≥0.5%（质量）时,材料的电阻率大幅度提高,其强度反而急剧下降。     

ZrO2对钼铼合金微观组织与性能的影响

钼铼合金具有优良的力学性能和机加工性能,是电子、核工业等领域关键的结构材料。在钼铼合金中加入氧化锆,形成弥散强化作用,并结合形变强化来提高材料的力学性能。研究发现,合金粉粒度随着ZrO₂含量的增加而减小,在含量为0.7%时晶粒尺寸最细小均匀;ZrO₂颗粒在合金的变形和断裂过程中表现出钉扎效应,显著提升合金的抗拉强度、屈服强度和断后延伸率等力学性能;ZrO₂强化钼铼合金的抗拉强度和断后延伸率在ZrO₂含量为0.7%时达到最高值,随后减少;ZrO₂基本弥散分布在晶界处并与钼基体形成良好结合界面,可以抑制晶界的迁移,提高钼合金的变形抗力。     

碳钢–橡胶硫化黏接拉伸力学行为与黏接失效机理

目的 研究碳钢-橡胶黏接结构件的拉伸力学行为和黏接失效机理,同时获得黏接工艺参数对碳钢-橡胶黏接界面质量的影响规律。方法 引入内聚力模型来描述黏接界面的黏接失效过程,通过黏接结构件界面力学性能实验拟合,获得内聚力参数,建立碳钢-橡胶黏接三维拉伸数值模型,从拉伸应力、剥离应力、损伤因子和刚度弱化的角度分析碳钢-橡胶在拉伸载荷作用下的黏接失效行为,研究刚度、初始损伤强度和断裂能对碳钢-橡胶黏接界面力学性能的影响规律。结果 在实验得到的内聚力参数下,碳钢-橡胶黏接界面中部最大拉伸应力比边缘增大了0.42 MPa,黏接界面边缘的最大剥离应力比最大拉伸应力增大了0.77 MPa。在拉伸位移为1.35 mm时,黏接界面中部最先进入损伤演化。当拉伸位移增至1.8 mm时,黏接界面边缘进入损伤演化,黏接界面中部完全失效,刚度的减小使得黏接界面的抗拉伸能力增强,刚度越小黏接界面的抗拉伸能力增强效果越明显。初始损伤强度小于3.42 MPa,黏接界面损伤演化速度明显较慢,在较大拉伸位移下才会发生黏接失效。不同断裂能的黏接界面进入损伤演化时的拉伸位移一致,断裂能越大的黏接界面损伤演化至完全失效的速度越慢。结论...