热处理对Cr17Ni2钢组织和冲击韧性的影响

本文研究了热处理理论对 Cr17Ni2钢组织和冲击韧性的影响,结果表明,将淬火温度提高至1050℃以上,可大大提高冲击韧性。晶界和相界上(Cr、Fe)_(23)C_6碳化物的溶解是冲击韧性增加的主要原因;此外,板条间残留奥氏体薄膜对冲击韧性提高也有贡献。冲击断口的结构可反映断裂特征的组织情况。考虑到室温力学性能,作者建议了合适的热处理工艺,生产中虚用效果良好。     

回火温度对1Cr15Ni4Mo3N钢组织和性能的影响

研究了回火温度对1Cr15Ni4Mo3N钢组织和性能的影响.结果表明,组织中具有高密度位错的板条马氏体及与基体共格的细小沉淀相M2C是该钢具有高强度的主要原因.470℃左右回火强度达到峰值,冲击韧性处于低谷.     

Al_2O_3-ZrO_2/W/Cr/Ni/Co金属陶瓷的断裂韧性

以Al2O3-ZrO2复合粉末、W、Cr、Ni、Co粉末为原料,采用热压烧结工艺制备了性能优良的Al2O3-ZrO2/W/Cr/Ni/Co金属陶瓷复合材料。通过SEM,EDS,XRD等手段分析其微观组织,单边梁开口法(SENB)测量其断裂韧性。实验结果表明在1320℃,20MPa条件下热压烧结制备的Al2O3-ZrO2/W/Cr/Ni/Co金属陶瓷的断裂韧性为7.16±0.4MPa.m1/2,硬度为83.3HRA,横向断裂强度为540MPa,相对致密度为97.4%;对维氏压痕下裂纹扩展进行了分析,其增韧机理为延性金属对裂纹的桥梁作用和氧化锆相变增韧,在裂纹通过时硬质相以沿晶断裂为主。     

TiCp/Cr15高铬铸铁复合材料的制备与性能

以TiC_p粉末和水雾化Cr15高铬铸铁粉末为原料,采用粉末冶金液相烧结技术制备TiC_p增强高铬铸铁复合材料。研究了TiC_p含量对高铬铸铁的物相组成、显微组织和力学性能的影响。研究结果表明,全致密的TiC_p增强高铬铸铁基体复合材料的构成相为TiC、M₇C₃型碳化物、马氏体和少量奥氏体;随着TiC_p添加量增大,金属基体逐步呈孤岛状,并在其中析出越来越多的M₇C₃型碳化物,同时TiC_p逐步呈连续网状分布;同时,其硬度稳步提升,而抗弯强度和冲击韧性降低。当TiC_p添加量为20wt%时烧结态复合材料具有最佳综合力学性能。此时硬度为HRC 66.8 ,冲击韧性为6.86 J/cm2,抗弯强度为1 343.10 MPa。当TiC_p添加量为25wt%时硬度达到最大值HRC 67.20 。      

4Cr14Ni14W2Mo钢中的碳化物

本文研究了4Cr14Ni14W2Mo 钢中碳化物的性态,溶解和析出规律及其对性能的影响。指出,该钢中存在球形、立方体形和六方柱体形等多种形态碳化物,但均为 M_(2(?))C_6。较低温度时效析出的碳化物为立方体形,细小弥散,与基体共格,有明显强化作用。未溶碳化物和较高温度二次固溶后析出的碳化物多为球状和六方柱体形,尺寸较大,与基体不共格,强化作用有限。二次固溶沿晶界择优析出的粗大链状碳化物和时效沿晶析出的网状碳化物易导致沿晶断裂。     

（Ni,Cr）／Al2O3复合涂层制备工艺的研究

利用粉末热喷涂法制备（Ｎｉ，Ｃｒ）／Ａｌ２Ｏ３复合涂层，采用ＸＲＤ和金相对复合涂层的相结构和相组成进行分析，并分析了喷涂工艺对金属／陶瓷系复合涂层制备的影响。实验结果表明，Ａｌ２Ｏ３粉末的沉积率和喷涂参数是影响（Ｎｉ，Ｃｒ）／Ａｌ２Ｏ３复合涂层相结构和相组成的关键。     

双相不锈钢00Cr25Ni7Mo4N敏化过程中的脆化机理研究

研究了双相不锈钢00Cr25Ni7Mo4N在晶间腐蚀试验中发生的脆断现象,采用金相法、扫描电镜和透射电镜对材料的脆断机理进行了分析。研究发现双相不锈钢00Cr25Ni7Mo4N在敏化时有R相、Fe3Cr3Mo2Si2相等脆性相析出,导致材料脆化,冲击韧性下降。最后,给出了双相不锈钢00Cr25Ni7Mo4N热加工后的使用要求。     

时效温度对0Cr17Ni4Cu4Nb钢组织及力学性能的影响

以0Cr17Ni4Cu4Nb马氏体沉淀硬化不锈钢为研究对象,分析了不同时效温度对其显微组织和力学性能的影响,并对试样断口特征进行了观察分析。结果表明:随着时效温度的升高(480~550℃),材料的抗拉强度σb和屈服强度σp0.2呈逐渐下降的趋势,而材料的断面收缩率Ψ和伸长率δ5呈逐渐上升的趋势;材料的冲击韧性aku受时效温度的影响比较明显,呈逐渐上升的趋势,其中在550℃时aku达到213.4(J·cm-2)。同时由断口观察分析结果显示,时效温度为550℃时拉伸断口的放射区最小,其塑性最好;冲击断口塑性变形最为明显,纤维区和剪切唇区所占的比例最大。0Cr17Ni4Cu4Nb不锈钢随着时效温度的升高,淬火马氏体基体开始回复、再结晶,逆转变奥氏体开始生成并长大,导致材料中的残余奥氏体含量增加,而残余奥氏体的存在有利于0Cr17Ni4Cu4Nb不锈钢保持良好的塑性和韧性。     

20Cr2Ni4钢制打击罩硬度异常分析

某批20Cr2Ni4钢制打击罩硬度出现异常,导致机加工刀具寿命严重降低。通过宏观分析、化学成分分析、硬度分析和金相检验等方法对打击罩异常件和正常件进行了对比分析。结果表明:该钢热加工后产生了硬度较高的粒状贝氏体,后续正火+高温回火热处理可以使粒状贝氏体分解从而降低产品硬度;异常件为未经热处理的产品,其奥氏体晶粒粗大,硬度偏高,从而导致刀具损坏严重。建议产品分类摆放,加强现场管理和监控力度。     

18Cr2Ni4W齿轴开裂分析

对开裂的１８Ｃｒ２Ｎｉ４Ｗ齿轴的非金属夹杂，金属相组以及显微硬度进行了分析。结果表明，齿轴的开裂是由于淬火温度偏高，形成淬火裂纹所致。     

10Cr4Ni4Mo4V钢和Cr4Mo4V钢的特性与断裂行为

对１０Ｃｒ４Ｎｉ４Ｍｏ４Ｖ钢和Ｃｒ４Ｍｏ４Ｖ钢的特性与断裂行为进行了试验研究。结果表明,１０Ｃｒ４Ｎｉ４Ｍｏ４Ｖ钢经微氮渗碳热处理后,其表面硬度、残余应力、断裂韧性及裂纹扩展速率均优于Ｃｒ４Ｍｏ４Ｖ钢的。     

0Cr17Ni4Cu4Nb钢锻件延迟断裂失效分析

通过化学分析、力学性能检测、表面残余应力检测、金相检验和断口分析的方法,分析了0Cr17Ni4Cu4Nb钢锻件开裂的原因,结果显示,该锻件的开裂是由于回火不足引起的应力腐蚀开裂。     

New Al–Mg–Li–C dispersion strengthened alloy Part 2 – Optimisation of material for forging applications

Abstract

This paper describes work aimed at optimising the forging process and mechanical properties of a new powder route Al–Mg–Li–C dispersion strengthened alloy, specifically for forging applications. The alloy, of the AA 5091 type, has a nominal composition of Al–1.2Li–5Mg–0.35C (wt-%), and is non-heat treatable. Materials were supplied by AMC Ltd, and evaluated in laboratory based forging trials to determine the influence of forging parameters on mechanical properties, including an investigation of using extruded bar as forging stock. The process was scaled up to produce an industrial forging, using an EH101 helicopter part, which was cut up for detailed mechanical property assessment. It was found that adequate hot working of the material is needed for good toughness, and that the balance of strength to toughness can be controlled by the forging temperature. The new alloy, in the as forged condition, meets the minimum tensile and fracture toughness levels set in the draft AECMA Specification for AA 5091 forgings.     

Die Messung der Bruchzähigkeit eines Vergütungsstahles mit Hilfe der Teilentlastungsmethode

Application of the Unloading Compliance Method in Fracture Toughness Measurements of a Quenched and Tempered Steel The application of the J-integral leads to a considerable reduction of material needed for establishing toughness data. The number of specimens is further reduced by measuring the crack resistance curve in a single specimen. This requires monitoring the crack extension during the experiment. A comparison of several methods showed that the unloading compliance technique is particularly suitable for that purpose. This method was applied for measuring the toughness as a function of location in a large forging of a steel 25 NiCrMo 14 5. Good toughness values (about 200 MPam^1/2) with little scatter were found over the whole cross section of the forging.     

Solidification microstructure of Cr4Mo4V steel forged in the semi-solid state

Semi-solid forging of iron-based alloys during solidification has unique characteristics distinct from those of the classical hot forging. With the aim of acquiring precise knowledge concerning the microstructural evolution of bearing steel Cr4 Mo4 V in this process, a series of semi-solid forging experiments were carried out in which samples were wrapped in a designed pure iron sheath. The effects of forging temperature and forging reduction on the grain morphology and liquid flow behavior were investigated, respectively.By forging solidifying metal(FSM), bulky primary dendrites were broken and spheroidal grains with an average shape factor of 0.87 were obtained at 1360?C. With the decreasing forging temperature to 1340?C,the microstructural homogeneity can be improved. On the other hand, it shows that a higher forging reduction(50%) is essential for the spheroidization of grains and elimination of liquid segregation. Those microstructural characteristics are related to different motion mechanisms of solid and liquid phases at different forging temperatures. Additionally, the effect of semi-solid forging on the eutectic carbides was also investigated, and the results demonstrate that the higher diffusion capacity and less liquid segregation jointly lower the large eutectic carbides and consequently cause its uniform distribution during FSM.     

热处理对00Cr26Ni6Mo4Cu1Ti铁素体时效不锈钢力学性能的影响

研究了热处理工艺对００Ｃｒ２６Ｎｉ６Ｍｏ４Ｃｕ１Ｔｉ铁素体时效不锈钢力学性能的影响，提出了适用于该合金的最佳热处理工艺规范。为大规格锻棒的热处理提供了参考。     

022Cr25Ni7Mo4N双相不锈钢等温处理中的组织演变EI北大核心CSCD

研究经1100℃等温处理2~20 h后022Cr25Ni7Mo4N双相不锈钢的显微组织演变。观察钢中奥氏体晶粒形态变化并对其尺寸进行定量表征,测量铁素体/奥氏体两相中的元素含量变化,并探讨组织演变对实验钢中铁素体相体积分数的各向异性和低温冲击韧性的影响。结果表明:随着保温时间的延长,奥氏体晶粒发生聚集、长大、粗化现象,并伴随显著的晶粒形态变化,a/b值≥4.0时细长棒状晶粒体积分数从近20%骤降至5%以下,a/b值介于1.0~1.9的等轴晶粒体积分数显著上升的同时,尺寸≥20μm的晶粒体积分数快速增加。保温时间的延长使得Mo,Cr元素进一步向铁素体相扩散、富集,并提高铁素体相抗点蚀当量(pitting resistance equivalent number,PREN)值。细长棒状奥氏体晶粒比例的显著下降,是奥氏体体积分数各向异性改善和实验钢低温冲击韧性提高的主要原因。     

电磁场对高速钢与45钢感应摩擦焊接的影响

利用电磁场对金属材料产生的"场致效应",调节摩擦焊接表面的温度场,以改善异种金属摩擦焊接组织及性能.研究了外加电磁场对W6Mo5Cr4V2高速钢和45钢摩擦焊缝显微组织、合金元素扩散及焊接接头力学性能的影响.结果表明,摩擦加热阶段施加电磁场使45钢近缝区铁素体的数量减少;而在顶锻阶段施加电磁场,使45钢侧铁素体数量有所增多.同时,在顶锻阶段施加电磁场作用时,主要合金元素C、Cr、W的扩散区宽度明显增大.在顶锻阶段采用较短的电磁场施加时间和较低的感应电流强度,可以提高W6Mo5Cr4V2高速钢和45钢摩擦焊接头的抗拉强度.     

络合溶胶-凝胶法制备氧化物弥散强化 12Cr钢中氧化物的形成机制

以乙二胺四乙酸(EDTA)为络合剂, 采用EDTA络合溶胶-凝胶法向氩气雾化制备的预合金粉末中添加Y₂O₃, 复合粉通过热等静压致密化, 锻造后固溶处理, 制得化学成分为Fe-12Cr-2.5W-0.25Ti-0.2V-0.4Y₂O₃ (0.4Y₂O₃/12Cr, 质量分数, %)的氧化物弥散强化(ODS) 铁素体钢(12Cr)。采用SEM、FE-SEM、XRD对复合粉末、热等静压态和锻造态Y₂O₃/12Cr铁素体钢中的氧化物的形成过程和行为进行了分析和表征。结果表明: 化学法制备的Y₂O₃弥散强化0.4Y₂O₃/12Cr铁素体钢中氧化物的形成机制有络合热分解机制、界面反应机制和再析出机制。通过选择合适的工艺参数和机械分散作用可获得细小均匀的氧化物强化相。      

Replacement of conventionally complex processing for low alloy steel 20Cr2Ni4A by rare earth carburising at lower temperature

Abstract

This paper deals with the effects of rare earth (RE) addition on the microstructure and properties of 20Cr2Ni4A steel carburised at 860°C. Compared with conventional 920°C carburising and other complex treatments, finer and more dispersed carbide precipitates formed in the surface layers. A superfine martensitic structure and a less residual austenite were obtained by direct quenching after RE 860°C carburising. The microstructure exhibited a higher microhardness, a wear resistant surface layer, and it also led to an increase in impact toughness. In addition, the heat treatment period for this steel was remarkably reduced by the replacement of conventional complex treatments by RE 860°C carburising.