应力腐蚀门限值δSCC的恒载荷多试样测定法

为评定金属材料在弹塑性状态下的δＳＣＣ敏感性，以现行国家标准为基础，提出了弹塑性状态下应力腐蚀断裂韧性门限值δＳＣＣ的概念和恒载荷多试样测定法．实验中的裂纹起裂时间由挠度－时间曲线的转折点确定，避开了直接观测的困难．所得结果与用其他方法得到的基本一致．     

ZG06Cr16Ni5Mo中δ铁素体对弯曲性能的影响

研究了ＺＧ０６Ｃｒ１６Ｎｉ５Ｍｏ 铸钢中δ铁素体形态和分布对铸钢塑性、韧性和弯曲性能的影响； 探讨了δ铁素体的分布在材料弯曲变形时的作用； 同时提出了改善δ铁素体形态和分布的措施。     

不锈钢焊缝金的氢脆

用慢应变速率拉伸方法研究了不稳定型奥氏体不锈钢焊缝金属（３０８Ｌ和 ３４７Ｌ）以及母材（３０４Ｌ）的氢脆敏感性,分别研究了原子氢以及氢致马氏体对氢致塑性损失的贡献,结果表明,当可扩散的氢浓度Ｃ０大于临界值（约 ２５×１０－６－３０×１０－６）后三种不锈钢均会出现氢致马氏体（ε＋α’）,其含量 Ｍ随 Ｃ０升高而升高,即 Ｍ（ε＋α’）＝５４．２－２５ ｅｘｐ（－Ｃ０／１５３）．氢致马氏体引起的塑性损失Ｉδ（Ｍ）随马氏体含量线性升高,即 Ｉδ（Ｍ）＝０４５Ｍ＝２４．４－１１．３ ｅｘｐ（－Ｃ０／１５３）１００％马氏体引起的最大塑性损失约为 ４５％,动态充氢引起的塑性损失几减去充氢除气试样的塑性损失就是原子氢引起的塑性损失Ｉδ（Ｈ）,它随 Ｃ０升高而升高,但当 Ｃ０＞１０－４后,Ｉδ（Ｈ）趋于最大值（对应 ε＝５ × １０－６／ｓ）,即 Ｉδ（Ｈ）ｍａｘ＝４４％（３０８Ｌ）,Ｉδ（Ｈ）ｍａｘ＝４５％（３４７Ｌ）以及 Ｉδ（Ｈ）ｍａｘ＝４０％（３０４Ｌ）．随应变速率ε升高,Ｉδ（Ｈ）逐渐下降,直至为零（对应 ε＝０．０１８／ｓ—０．０３２／ｓ）;即 Ｉδ（Ｈ）＝－１６．４—１０．６ ｉｇε（３０８Ｌ）,Ｉδ（Ｈ）＝－２０．９—１２．１     

不同Ce含量的1420合金的时效过程

测定了含Ｃｅ０．０６ｗｔ％及０．１５ｗｔ％的１４２０合金板材的时效硬化曲线及室温力学性能，分析了Ｃｅ对１４２０合金时效过程的影响。结果表明：Ｃｅ含量在０．１５ｗｔ％范围内的１４２０合金时效的组织与不含Ｃｅ的１４２０合金类似，主要强化相为δ＇及δ＇／β＇复合相。微量Ｃｅ在１４２０合金中可以减缓固溶处理时的再结晶过程及细化再结晶晶粒，并促进δ＇相在时效过程中的弥散析出。添加０．０６Ｗｔ％Ｃｅ时有利于提高合金塑性，而添加０．１５ｗｔ％Ｃｅ时则有利于提高合金强度。采用４６５℃固溶，２％预拉伸变形及１７０℃／６ｈ时效，可使含微量Ｃｅ的１４２０合金板材获得较好的综合力学性能。     

ZG06Cr16Ni5Mo中δ的素体对弯曲性能的影响

研究了ＺＧ０６Ｃｒ１６Ｎｉ５Ｍｏ铸钢中δ铁素体形态和分布对铸钢塑性，韧性和弯曲性能的影响；探讨了δ铁素体的分布在材料弯曲变形时的作用；同时提出了改善δ铁素体形态和分布的措施。     

PROCESS CHARACTERISTICS OF HoBa_2Cu_3O_（7－δ） AND EFFECT OF MAGNETIC FIELD ON SUPERCONDUCTIVITY OF REBa_2Cu_3O_（7－δ） （RE＝Y，Ho）

ＰＲＯＣＥＳＳＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＨｏＢａ_２Ｃｕ_３Ｏ_（７－δ）ＡＮＤＥＦＦＥＣＴＯＦＭＡＧＮＥＴＩＣＦＩＥＬＤＯＮＳＵＰＥＲＣＯＮＤＵＣＴＩＶＩＴＹＯＦＲＥＢａ_２Ｃｕ_３Ｏ_（７－δ）（ＲＥ＝Ｙ，Ｈｏ）￥Ｙｉ，Ｊｉａｎｈｏｎｇ；Ｐｅｎ...     

Quantum Chemical Calculation on Preparation of YBa＿2Cu＿3O＿（7－δ） Powders by Hydrolysis of Metal Alkoxides

ＱｕａｎｔｕｍＣｈｅｍｉｃａｌＣａｌｃｕｌａｔｉｏｎｏｎＰｒｅｐａｒａｔｉｏｎｏｆＹＢａ＿２Ｃｕ＿３Ｏ＿（７－δ）ＰｏｗｄｅｒｓｂｙＨｙｄｒｏｌｙｓｉｓｏｆＭｅｔａｌＡｌｋｏｘｉｄｅｓＹｉｎＺｈｏｕｌａｎ；ＬｉＸｉｎｈａｉ；ＺｈａｏＱｉｎｓｈｅｎｇ；...     

激光熔覆WC—Ni复合涂层的结构和性能

研究了两种激光熔覆ＷＣ－Ｎｉ涂层，均满足柴油机飞轮的技术要求。给出了两种ＷＣ－Ｎｉ涂层的金相组织、显微硬度及Ｘ光相分析结果。ＷＣ－Ｎｉ涂层的硬化相是δ－ＷＣ、β－Ｗ２Ｃ、Ｍ＾Ｃ、Ｍ１２Ｃ及少量ｒ－ＷＣ。     

Electron Microscopy Studies of Magnetron Sputtered YBa＿2Cu＿3O＿（7－δ） Thin Films

ＥｌｅｃｔｒｏｎＭｉｃｒｏｓｃｏｐｙＳｔｕｄｉｅｓｏｆＭａｇｎｅｔｒｏｎＳｐｕｔｔｅｒｅｄＹＢａ＿２Ｃｕ＿３Ｏ＿（７－δ）ＴｈｉｎＦｉｌｍｓＳｈａＷｅｉ沙维（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓ，ＩｍｐｅｒｉａｌＣｏｌｌｅｇｅ，ＰｒｉｎｃｅＣｏ...     

热处理对Cr17Ni2钢组织和硬度的影响

研究了热处理对Ｃｒ１７Ｎｉ２钢组织和硬度的影响。结果表明，随淬火温度由９５０℃升高到１１００℃，组织中δ铁素体略有增加，而硬度持续增加，回火对δ铁素体数量没有影响，研究还发现该钢的硬度是基体和δ铁素体的综合贡献，存在如下近似关系式ＨＶ＝ＨＶＭ（１－ｆＦ）＋ＨＶＦｆＦ。     

Microstructure and fracture toughness of Ti(C0.7N0.3)-WC-Ni cermets

Mo₂C is normally added to improve the wettability between Ti(C,N) and Ni in Ti(C,N)-based cermets. Due to the increasing price of Mo₂C, much attention has been paid to Ti(C,N)-based cermets with WC addition. In this paper, effect of WC content on the microstructure and properties of Ti(C_0.7N_0.3)-xWC-15wt.%Ni cermets free of Mo₂C was studied. The experimental results show that the microstructure is refined obviously with the increase of WC content. The fracture toughness decreases with the increase of WC content when WC content is 10-25 wt.%, and increases when WC content varies from 25 wt.% to 30 wt.%.     

Microstructure Characterization and Fracture Toughness of Laves Phase-Based Cr–Nb–Ti Alloys

Three Laves phase-based alloys with nominal compositions of Cr2Nb–x Ti(x = 20,30,40,in at%) have been prepared through vacuum non-consumable arc melting.The results show that the microstructures of Cr2Nb-(20,30) Ti alloys are composed of the primary Laves phase C15–Cr2(Nb,Ti) and bcc solid solution phase,while the microstructure of Cr2Nb–40Ti alloy is developed with the eutectic phases C15–Cr2(Nb,Ti)/bcc solid solution.The measured fracture toughness of ternary Laves phase C15–Cr2(Nb,Ti) is about 3.0 MPa m1/2,much larger than 1.4 MPa m1/2for binary Laves phase Cr2 Nb.Meanwhile,the fracture toughness of Cr2Nb–x Ti(x = 20,30,40) alloys increases with increasing Ti content and reaches 10.6 MPa m1/2in Cr2Nb–40Ti alloy.The eutectic microstructure and addition of Ti in Cr2 Nb are found to be effective in toughening Laves phase-based alloys.     

Fracture and creep of an Al2O3-SiC (whisker)-TiC (particle) composite

High-temperature fracture strength and compressive creep of an electrodischarge-machinable composite, Al₂O₃-30.9 vol.% SiC whiskers-23 vol.% TiC particles have been studied to 1200 °C and 1450 °C, respectively, in inert atmosphere. Microstructures of fractured and deformed specimens were examined using scanning and transmission electron microscopy. Fast fracture occurred at T ≤ 1200 °C. Steady-state creep was achieved for T > 1350 °C at stresses < 80 MPa, with the rate-controlling mechanism being partially unaccommodated grain-boundary sliding, with a stress exponent of ≈ 1 and an activation energy of≈ 470 kJ/mol.     

EFFECT OF Mo AND Mo2C ON THE MICROSTRUCTURE AND PROPERTIES OF THE CERMETS BASED ON Ti（C,N）

Effect of Mo and Mo2 C on the microstructure and properties of Ti（C,N）-based cermets was investigated in this article. The results have indicated that the weight percentage of Mo from 5 to 10 can reduce Ti（C,N） grain diameter and thickness of the rim, and Ti（C,N） grain can be wetted by Ni-Cu-Mo liquid so as to get small contiguity of Ti（C,N） grain. In that way, the transverse rupture strength of Ti（C,N）-based cermets has reached 1800-1900 MPa; the fracture toughness has been due to 16-18 MPa.m1/2. But 15 wt pct Mo was not more effective on Ti（C,N）-based cermets, because the thickness of the rim becomes larger. In the circumstance of Mo2 C, 5 wt pct Mo2 C was good for microstructure and properties of Ti（C,N）-based cermets, but 11 wt pct Mo2C has resulted in larger contiguity of Ti（C,N） grain and big Ti（C,N） grain diameter so as to reduce transverse rupture strength and fracture toughness. So that, the effect of Mo on Ti（C,N）-based cermets is better than Mo2C.     

Ductile fracture prediction in cold forging process chains

The paper presents a new approach for the prediction of ductile fracture occurrence in multi-stage cold forging process chains. The approach combines the fracture criterion proposed by Xue and Wierzbicky with a linear damage accumulation law. Thanks to this feature, the approach is capable of predicting both the location where the failure events occur under the action of external loading and the time they take to be generated. An application to the multi-stage cold forging of a C35 Torx-type socket screw carried out on a double-blow header is presented and results of predictions are compared with experimental observations.     

MAR-M247合金高温断裂机制的原位研究

利用原位高温拉伸台在扫描电镜中研究了镍基铸造高温合金MAR-M247在室温、400 ℃与760 ℃拉伸过程中的动态组织演变和断裂机制。原位测试结果表明,在室温到760 ℃范围内,MAR-M247合金的屈服强度与抗拉强度随温度的升高略有下降,拉伸塑性略有提高。室温原位拉伸过程中,并没有出现滑移带;400 ℃与760 ℃的原位拉伸,只在样品断口附近存在少量的滑移带。随拉伸温度的提高,合金的断裂机制并无明显变化,均表现为韧性穿晶断裂。合金的微裂纹主要来源于变形过程中碳化物的破裂,晶内与晶界都存在因碳化物破裂而形成的微裂纹。     

Fracture of Magnesium Alloy in Cold Forging

In order to clarify the forming limit of magnesium alloy in cold forging, the workability of magnesium alloy AZ31B (Mg-3%Al-1%Zn) is examined by upsetting and backward extrusion. In the upsettability test, shear type fracture occurs at a small equivalent strain of about 0.15 at temperatures lower than 170 °C. At a higher temperature, the flow stress curve has a peak at an average equivalent strain of 0.2-0.3, showing a clear tendency to work soften. In cold backward extrusion with a conical punch, the local strain can reach a very large value, 3.0 or greater, without fracture. To explain the experimental results, the mechanism of fracturing is discussed on the basis of strain localization, and a fracture criterion of magnesium alloy in cold forging is suggested. The newly proposed criterion provides much better results than the existing criteria.     

Mechanical properties and fracture behavior of an Nb-Silicide in situ composite

An Nb-Silicide in situ composite with a nominal composition of Nb-16Si-10Ti-10Mo-5Hf (at. %) was fabricated by mechanical alloying followed by hot-pressing sintering. The microstructure consisted of an Nb solid solution, Nb₅Si₃ and a small amount of Nb₃Si. This in-situ composite exhibited good balance of strength between ambient temperature and high temperatures; the ultimate tensile strength was 413 and 496 MPa at room temperature and 1200 °C, respectively. The tensile fracture behavior was dominated by cleavage of the Nbss and Nb₅Si₃ at 1200 °C and lower temperatures. However, the fracture behavior was governed by ductile rupture of Nbss at 1300 °C and higher temperature, which was ascribed to both the increased ductility of Nbss and the decreased interface strength. At 1400 °C and higher temperature, the material exhibited extensive plasticity or superplasticity; the dominant deformation mechanism was grain boundary sliding at 1400 °C and higher temperature.     

Nanoscratching deformation and fracture toughness of electroless Ni-P coatings

In the present investigation electroless Ni-P coatings were prepared. Structural characterizations indicated that the as-deposited coating had an amorphous structure with a P content of 23 at.%. The deformation behavior of an electrolessly amorphous Ni-P coating was investigated by using the Vickers indentation and the Tribo-indenter instrumented nano-indentation technique. The hardness of the Ni-P coating is remarkably improved after proper heat-treatment and the hardness is as high as 12.7 GPa for the coating annealed at 400 °C for 1 h. However, the cracks were observed during the indentation of the Ni-P coatings annealed at 400 °C and 500 °C for 1 h. The corresponding fracture toughness was evaluated as 2.58 MPa m^0.5 and 1.33 MPa m^0.5, respectively. Nanoscratching tests indicated that the wear resistance of the Ni-P coatings was improved significantly with an increasing ratio of hardness (H) to elastic modulus (E). It was observed that the friction coefficient increased from 0.083 ± 0.006 for the Ni-P coating annealed at 300 °C up to 1.337 ± 0.009 for the IF steel substrate, while the H/E simultaneously decreased from 0.084 (10.7/128) to 0.009 (1.85/200). The study revealed that the electrolessly amorphous Ni-P coating had offered better corrosion resistance than the Ni-P coatings after heat-treatment. An annealing temperature of 300 °C is preferentially suggested for the trade-off between the wear resistance property and anti-corrosion property of the Ni-P coating.     

A Newly Developed Wrought Ni-Fe-Cr-based Superalloy for Advanced Ultra-Supercritical Power Plant Applications Beyond 700 °C

Some existing wrought Ni-Cr-Co-based superalloys are being evaluated as the candidate materials for advanced ultra-supercritical power plant applications beyond 700 °C due to their high creep strength. But they are all prohibitively expensive due to the addition of Co, Mo and W. Here we developed a new Ni-Fe-Cr-based superalloy (named as HT700 alloy) with low cost and high strength. This paper reports the mechanical properties and fracture modes of HT700 alloy to support its high temperature applications and to understand prospective failure mechanism. Fractographic examinations indicate that the fracture modes shift with test condition change. In addition, the HT700 alloy has relatively stable microstructure at 750 °C. Compared with IN740 and GH2984 alloys, this new alloy has higher yield strength in the temperature range from room temperature to 800 °C. The creep life of this new alloy is much longer than that of the Ni-Fe-based superalloy GH2984. The results suggest that this new alloy is a promising material for advanced ultra-supercritical power plant applications beyond 700 °C.