W-Ni-Fe高比重合金的表面强化

为了增强W－Ni-Fe高比重合金表面层的硬度和耐磨性能,采用等离子喷涂和真空熔结的方法,在W－Ni-Fe高比重合金表面获得一定厚度的涂层,并通过扫描电镜观察,探讨了涂层的显微组织及涂层与基体的结合机理,并着重分析了真空熔结涂层中裂纹形成的原因。     

钛合金表面强化新进展

介绍了为改善钛合金表面耐磨性将激光表面熔敷、高能微弧火花渗碳和表面渗氧技术应用于钛合金表面强化所取得的进展。讨论了每种工艺方法所获表面改性层的结构和性能特征及其应用范围。     

钛合金表面强化新进展

介绍了为改善钛合金表面耐磨性将激光表面熔敷、高能微弧火花渗碳和表面渗氧技术应用于钛合金表面强化所取得的进展。讨论了每种工艺方法所获表面改性层的结构和性能特征及其应用范围。     

A Novel Heat Treatment Process for Surface Hardening of Steel: Metal Melt Surface Hardening

A novel heat treatment process for surface hardening of steel has been demonstrated and named as “metal melt surface hardening (MMSH).” A surface layer with a thickness of about 400 μm and a hardness of about 700 HV has been achieved by ejecting AISI 304 stainless steel melt at a temperature of about 1783 K (1510 °C) onto the 40Cr steel surface. This proposed MMSH provides a very promising application for surface hardening of steel.     

Precipitation and Hardening in Magnesium Alloys

Magnesium alloys have received an increasing interest in the past 12?years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.     

Ti(C,N)基硬质合金中的润湿性研究

主要研究内容包括如下几个方面： 粘结相 Ｎｉ－ Ｃｏ（ Ｎｉ ∶ Ｃｏ ＝ １ ∶１ , 质量比, 下同） 与不同 Ｎ／ Ｃ 比的硬质相 Ｔｉ（ Ｃ, Ｎ）（ Ｔｉ Ｎ／（ Ｔｉ Ｃ＋ Ｔｉ Ｎ） ＝ ０ ．１ ,０ ．３ ,０ ．５ ,０ ．７ ,０ ．９） 之间的润湿规律;粘结相 Ｎｉ－ Ｃｏ － Ｍｏ , Ｎｉ － Ｃｏ － Ｔａ , Ｎｉ－ Ｃｏ － Ｍｏ － Ｃ 与硬质相 Ｔｉ（ Ｃ, Ｎ） 之间的润湿情况;以及在 Ｔｉ（ Ｃ, Ｎ） 硬质相中添加 Ｔａ Ｃ, Ｎｂ Ｃ 等对润湿性的影响。研究表明,当硬质相中 Ｔｉ Ｎ／ （ Ｔｉ Ｃ＋ Ｔｉ Ｎ） ＜ ０ ．５ 时宜采用 Ｎｉ － Ｃｏ 作粘结相, 而当 Ｔｉ Ｎ／ （ Ｔｉ Ｃ＋ Ｔｉ Ｎ） ≥０ ．５时,则应选择 Ｎｉ－ Ｃｏ － Ｍｏ － Ｃ 作粘结相更适合。     

自蔓延高温合成法制备无钨硬质合金

用SHS同时致密化工艺制备的无钨硬质合金具有优异的性能，可以在很多应用领域中替代传统的WC－Co硬质合金，本文综述了SHS工艺合成无钨硬质合金的种类、性能、工艺条件、应用及发展前景。     

Mesostructuring in Sintered Hard Alloys

Theoretical principles are presented for mesostructure formation in sintered hard alloys.     

钒合金的沉淀析出行为和时效强化

采用真空退火和真空时效处理，研究了V-4Cr-4Ti合金的沉淀析出特性和时效强化效果。作为对比，同时研究了V-6W-1Ti或V-6W-4Ti合金的行为特征，以分析合金元素的作用。结果表明，在1h等时退火过程中，V-4Cr-4Ti的峰值沉淀强化温度出现在700℃，而其他两种合金出现在600℃。在600℃下时效1-393h，V-4Cr-4Ti表现出了更强的时效强化特性。两类合金的行为差异说明合金元素Cr在其中起了很大的作用，尽管微观分析显示析出物为Ti（CON）。经测试，V-4Cr-4Ti合金的延性并未因时效强化而发生显著变化，而拉伸试样的吸收功反而因时效强化而提高，表明合金的韧性得到了改善。     

Fracture Resistance Factors of Iron-Based Hard Alloys

The structural factors that determine the difference between the fracture strengths of iron-based hard alloys are estimated using the means of digital recording and measurement of structure and fracture surface images.     

Effect of Cerium on Microstructures of Hard Alloys

Microstructures and crack extending characteristic of the YG8R,YT5R and YT14R hard alloysadding a trace cerium were studied by AEM and HVEM with a tensile holder.In the hard alloys addingcerium,the compounds of Ce_2O_3 or Ce_2O_2S could be formed,extending of stacking faults and transforma-tion from fcc Co to hcp Co were suppressed,volume fraction of fcc Co in the alloys was increased,andstrength of Co and(TiW)C phases and grain boundaries were raised.Plastic deformation in Co phase nearedges of the tensile cracks was more strong,and the tensile cracks could pass through some smaller WCgrains.     

Age Hardening Behavior and Corresponding Microstructure of Dilute Al-Er-Zr Alloys

The age hardening and the microstructure of dilute Al-Er-Zr alloys were investigated by microhardness tests and TEM. The Al-0.04Er alloy shows a conventional age hardening behavior and obtains a maximum hardness of 410 MPa after aging for 2 h at 523 K (250 °C) due to precipitation of Al₃Er. The addition of Zr to Al-Er alloy can slow down the growth of the precipitates and make the age hardening effect remain for a long time in Al-0.04Er-0.04Zr alloy. Addition of Zr retards the decomposition of Al-Er and the Al-0.04Er-0.08Zr alloy can reach higher peak hardness than that of Al-0.04Er after aging for long time at elevated temperature. The precipitation behavior of Al-Er-Zr system is likely to be a new commercial way to developing creep-resistant aluminum alloy.     

Deposition of Protective Coatings on Tungsten-Free Hard Alloys

The process of deposition of coatings of titanium carbide, vanadium carbide, and chromium carbide on the surface of the tungsten-free hard alloys TN20, KNT16, and KKhN15 is investigated. The structure and phase composition of specially created layers are explored and the microhardness measured (11.5-24.5 GPa). The optimal temperature-time conditions for deposition of carbide coatings is determined. The ultimate transverse bending strength of hard alloys with and without coatings is determined. From the results of industrial tests, a two- to five-fold increase in the durability of plates in cutting was noted.     

A Combined Precipitation,Yield Strength,and Work Hardening Model for Al-Mg-Si Alloys

In the present article, a new two-internal-variable model for the work hardening behavior of commercial Al-Mg-Si alloys at room temperature is presented, which is linked to the previously developed precipitation and yield strength models for the same class of alloys. As a starting point, the total dislocation density is taken equal to the sum of the statistically stored and the geometrically necessary dislocations, using the latter parameters as the independent internal variables of the system. Classic dislocation theory is then used to capture the overall stress-strain response. In a calibrated form, the work hardening model relies solely on outputs from the precipitation model and thus exhibits a high degree of predictive power. In addition to the solute content, which determines the rate of dynamic recovery, the two other microstructure parameters that control the work hardening behavior are the geometric slip distance and the corresponding volume fraction of nonshearable Orowan particles in the base material. Both parameters are extracted from the predicted particle size distribution. The applicability of the combined model is illustrated by means of novel process diagrams, which show the interplay between the different variables that contribute to work hardening in commercial Al-Mg-Si alloys.     

铝合金-镁合金间搅拌摩擦异质焊接研究现状

综合了近几年铝-镁搅拌摩擦异质焊的研完成果,分析和讨论以下几个方面的内容:(1)铝.镁异质焊的焊接性能及其影响因素;(2)焊接过程中的热输入情况及焊缝处的温度分布;(3)焊缝的力学性能及其影响因素;(4)焊缝的宏观、微观组织及其在局部升温和塑性变形下的演化过程,着重分析了金属间化合物的生成、形貌和分布、及其对焊缝力学性...     

硬质合金粉末压制模具的设计

介绍了硬质合金粉末压制模具设计中要考虑的主要因素,并对模具的结构设计进行了详细探讨,有一定的参考价值。     

纳米硬质合金研究进展

文章综述了喷雾转化法纳米硬质合金制备工艺。阐述了适用于纳米硬质合金烧结的等离子活化烧结和微波烧结;介绍了晶粒长大抑制剂的种类、数量、加入方法对晶粒长大的影响．     

Tribological Properties of Hard Alloys Based on Chromium Carbide

Hard alloys of the type KKhN and KKhNF were studied and shown to have low coefficient of friction (f = 0.21-0.17) and wear rate (I = 5.7-7.0 m/km) at sliding velocity 15 m/sec and load 7 MPa, which make them promising for use as antifrictional materials in dry friction units under load. Oxide films formed at the surface of the hard alloys play the role of solid lubricants and decrease frictional losses.