38CrMoAlA钢的表面激光相变硬化层组织分析

为研究激光表面相变硬化对38CrMoAlA钢的表面耐磨性的影响,测定了该钢激光相变硬化层的显微硬度变化,并分析了该钢表面激光相变硬化层的微观组织。发现该硬化层由表及里可分四层,其中第二层显微硬度最高,第四层显微硬度最低。当采用激光束重叠扫描进行该钢的表面相变硬化时,重叠区域的回火软化效应可导致硬化效果有所降低,故光束重叠尺寸不可过高,本文选择1.2 mm。     

45钢激光束扫描数值模拟与组织性能北大核心CSCD

利用有限元软件ANSYS对激光束扫描试样的温度场进行数值模拟,研究其温度分布规律。研究激光束扫描对试样显微组织和性能的影响,探讨激光功率和扫描速度等工艺参数对相变硬化层组织性能的影响。采用光学显微镜分析45钢激光相变硬化区的显微组织,用显微硬度计进行硬度测量。结果表明:45钢经激光束扫描后,硬化层的显微组织为针状或板条状的马氏体,组织更加均匀、细小,试样表面硬度最高可达57.5 HRC,相比调质处理提高约1倍,激光扫描区域组织沿深度方向上成梯度分布规律,从表层往深度方向依次为相变硬化区、过渡区和基体。激光工艺参数对硬化层显微组织和性能有较大的影响,相变硬化层的深度和宽度随着激光功率的增加而增加,随着扫描速度的增加而减小;硬化层的截面硬度随着激光功率和扫描速度的增加呈现先增加后减小的变化规律。     

302HQA钢的冷变形硬化机理研究

通过Gleeble-1500上的室温压缩实验、微观组织分析、X-射线衍射分析、磁性测量等手段,系统研究了302HQA钢的冷变形规律。结果表明,302HQA钢冷变形过程的冷作硬化是位错塞积和形变诱发马氏体相变综合作用的结果;减少冷变形过程中形变马氏体的含量,可以降低冷镦钢成型过程的开裂现象。     

渗碳钢的显微组织

渗碳是制造承受重载的机器零件,如齿轮、轴和轴承的一种非常有效的工艺。就弯曲和接触疲劳而言,渗碳钢的抗弯曲、抗接触疲劳性能优于完全硬化钢和用其它表面硬化处理方法处理的钢。     

45钢激光束扫描数值模拟与组织性能

利用有限元软件ANSYS对激光束扫描试样的温度场进行数值模拟,研究其温度分布规律。研究激光束扫描对试样显微组织和性能的影响,探讨激光功率和扫描速度等工艺参数对相变硬化层组织性能的影响。采用光学显微镜分析45钢激光相变硬化区的显微组织,用显微硬度计进行硬度测量。结果表明:45钢经激光束扫描后,硬化层的显微组织为针状或板条状的马氏体,组织更加均匀、细小,试样表面硬度最高可达57.5 HRC,相比调质处理提高约1倍,激光扫描区域组织沿深度方向上成梯度分布规律,从表层往深度方向依次为相变硬化区、过渡区和基体。激光工艺参数对硬化层显微组织和性能有较大的影响,相变硬化层的深度和宽度随着激光功率的增加而增加,随着扫描速度的增加而减小;硬化层的截面硬度随着激光功率和扫描速度的增加呈现先增加后减小的变化规律。     

激光相变硬化处理对轮轨钢磨损性能影响

利用滚动磨损试验机研究了激光相变硬化处理前后轮轨钢试样的磨损与损伤性能。结果表明:激光相变硬化处理主要得到马氏体组织,显著提高轮轨试样的表面硬度,钢轨试样和车轮试样分别提高43.06%、44.39%;轮轨试样经激光相变硬化处理后滚动摩擦系数与未处理试样相差不大,单一处理轮轨试样摩擦系数有所增大;轮轨试样经激光相变硬化处理能明显提高轮轨试样表面抗磨损和变形能力,车轮试样磨损率减少约44.02%,钢轨试样减少约13.6%,单一处理轮轨试样虽能降低处理试样的磨损,但显著加剧对摩副的磨损;激光相变硬化处理后,钢轨试样表现为轻微疲劳磨损,车轮试样则是粘着磨损与疲劳磨损共存,以疲劳磨损为主;重载工况下轮轨钢试样均激光相变硬化处理能有效改善材料抗磨损和损伤能力。     

表面激光硬化轴承的疲劳失效分析

选用CO2激光器进行GCr15钢轴承滚道表面激光淬火处理试验,内圈硬化层深度可达到0.5 mm,外圈可达到0.45 mm.用金相显微镜、扫描电镜和X射线分析等现代测试技术对改性层的相组成及改性机理进行分析.结果表明,轴承表面的激光相变硬化可以产生具有较多残余奥氏体、细小碳化物以及过饱和的隐晶马氏体组织,从而提高轴承滚道表面的硬度.最后进行了轴承钢的接触疲劳性能试验.通过疲劳失效轴承表面的显微观察,验证了激光淬火套圈表面的疲劳失效形式仍为表层剥落.造成激光淬火套圈早期疲劳失效的主要原因是激光扫描开始与结束接口处没有完全对接上,以及硬化层深不均匀.     

32SiMnMoVA低合金超高强度钢激光相变硬化机理

研究了32SiMnMoVA低合金超高强度钢激光相变硬化后淬硬层的显微硬度分布和组织结构，探讨了其激光相变硬化机理，结果表明．激光淬硬层显微硬度分布主要与激光加热时所产生的温度场分布有关，激光相变硬化机理主要是马氏体强化和晶粒细化。     

TRIP钢研究的现状与发展

概述了相变诱发塑性（TRIP）钢的发展历史及研究现状;详细论述了TRIP钢中显微组织形成的机制和成分对显微组织和性能的影响;介绍了TRIP钢研究的最新技术,其内容包括TRIP研究的新试验技术和计算机模拟在高强度TRIP钢设计中的应用。最后,对TRIP钢的发展趋势做了展望。     

服役工况及喷丸强化对航空齿轮钢接触疲劳性能的影响

目的 针对不同服役工况和表面处理下航空齿轮钢接触疲劳性能不明确的问题,探究不同工况参数及喷丸强化对AISI 9310航空齿轮钢接触疲劳性能的影响。方法 基于双圆盘滚动接触疲劳试验台,对AISI 9310航空齿轮钢圆盘滚子试件在2种接触应力、3种滑差率的服役工况,以及渗碳磨削、喷丸强化2种工艺下开展滚动接触疲劳性能研究。使用白光干涉仪、X射线衍射应力仪和显微硬度仪对喷丸强化前后的表面形貌、残余应力和显微硬度进行表征,探究喷丸处理后的表面完整性与滚动接触疲劳性能之间的规律。结果 当接触应力由2.5 GPa增至3.0 GPa时,AISI 9310试件的滚动接触疲劳寿命降低了64.7%;当滑差率由10%增至20%、30%时,试件的滚动接触疲劳寿命分别下降了18.9%和42.8%,同时寿命分散性有所降低。此外,研究发现喷丸强化使试件表面残余压应力提升了104.3%,并形成了残余压应力层,表面显微硬度提升了4.8%,同时使试件的沟壑状刀痕转变为凹凸不平的弹坑,表面性状宽高比提升至0.931 0,更有利于润滑油的储存,从而使得试件的滚动接触疲劳寿命提升了87.8%。结论 获取了不同接触应力、滑差率和...     

Surface hardening by strain induced martensitic transformation

The hardness and fatigue strength achieved by strain hardening are normally noticeable lower than those attained by thermal or thermochemical heat treatments. Strain or deformation induced martensitic transformation of residual austenite can increase the strength achieved by mechanical surface hardening processes considerably. In this paper, an approach is presented where workpieces with a high content of metastable austenite are used for hardening the surface layer. The microstructure has to be sufficiently stable, in order to ensure that the material can be machined without being changed by strain induced transformation of the residual austenite. After machining, high Hertzian contact stresses are introduced by deep rolling, so that a strain induced martensitic transformation of the residual austenite takes place. At the same time deep rolling produces the surface finish of the part. By this method, a surface hardening without a heat treatment process within the production line can be realized. A conceivable use of this method could be the production of bearings or guideways.     

Comparative Study of Hardening Mechanisms During Aging of a 304 Stainless Steel Containing α′-Martensite

Strain aging and hardening behaviors of a 304 stainless steel containing deformation-induced martensite were investigated by examining mechanical properties and microstructural evolution for different aging temperature and time. Introduced age hardening mechanisms of a cold rolled 304 stainless steel were the additional formation of ????-martensite, hardening of ????-martensite, and hardening of deformed austenite. The increased amount of ????-martensite at an aging temperature of 450?°C confirmed the additional formation of ????-martensite as a hardening mechanism in a cold rolled 304 stainless steel. Additionally, the increased hardness in both ????-martensite and austenite phases with aging temperature proved that hardening of both ????-martensite and austenite phases would be effective as hardening mechanisms in cold rolled and aged 304 stainless steels. The results suggested that among hardening mechanisms, hardening of an ????-martensite phase, including the diffusion of interstitial solute carbon atoms to dislocations and the precipitation of fine carbide particles would become a major hardening mechanism during aging of cold rolled 304 stainless steels.     

深淬硬层冷轧辊用钢的端淬曲线

测定了不同冷轧辊用钢的端淬曲线、奥氏体晶粒度和接触疲劳寿命，结果表明：新型冷轧辊用钢的淬透深度达35-40mm，且具有低的过热敏感性和高的接触疲劳寿命。     

Influence of the relaxation processes on the structure formation in pure metals and alloys under high-pressure torsion

A study has been performed on three classes of materials in which different structure-forming processes dominate, namely, cold hardening in iron and structural steels, dynamic recrystallization in copper, and pressure-induced transformation in austenite steel. These processes are shown to affect a staged character of the structure formation upon high-pressure torsion. In the case of cold hardening, the character is controlled by true strain, the growth of which results in an increase in hardness and a refinement of the structure elements. The termination of these processes can be caused by another mechanism of relaxation, e.g. phase transformation induced by high pressure. Upon dynamic recrystallization, the staged character of deformation is determined by the temperature and rate of deformation.     

铌微合金化重载齿轮钢的疲劳性能

利用旋转弯曲疲劳试验方法研究了三种重载齿轮钢渗碳后的疲劳性能。结果表明,添加铌能够细化重载齿轮钢组织,提高渗碳层硬度,从而提高其疲劳强度。同时,疲劳裂纹在渗碳层沿原奥氏体晶界扩展,铌微合金化重载齿轮钢的晶粒细化,从而可以阻碍疲劳裂纹的扩展。此外,扫描电镜观察疲劳断口发现,重载齿轮钢渗碳后疲劳裂纹起源于基体或夹杂物,夹杂物尺寸越小,疲劳性能越好。     

节镍型奥氏体不锈钢冷轧断带的影响因素

对节镍型奥氏体不锈钢冷轧断带进行金相显微观测和电子探针分析.结果表明,形变诱发马氏体组织所加剧的加工硬化与冶炼时所产生的气孔缺陷的共同作用是冷轧断带的原因.保留必要的镍含量,工艺上选择合适的轧制工艺、中间退火是保证其冷轧质量的关键.     

Mechanical Properties and Retained Austenite Stability of High Aluminum TRIP-aided Cold-rolled Steel Sheets

The mechanical properties, microstructure and retained austenite stability of CMnAlSi-TRIP steels were investigated in this paper. The steel sheets were hot-rolled, cold-rolled and heat treated by intercritical annealing and isothermal heat treatment. The microstructure, volume fraction of retained austenite and its carbon concentration were observed by Optical microscopy and X-ray diffraction. The mechanical properties were obtained through uniaxial tensile test. The results show that the CMnAlSi cold-rolled TRIP-aided steels have good combination of strength and ductility with proper isothermal heat treatment, the retained austenite stability determines incremental strain hardening exponent during strain-induced martensitic transformation, and affected by its volume fraction and carbon content. The retained austenite stability has a good correlation with the combination of strength and ductility.     

Strain hardening of low-carbon manganese steels

Conclusions Low-carbon steels with a high manganese content (3–5%) are highly susceptible to strain aging, which is accompanied by hardening due to precipitation of finely dispersed cementite particles. The increase of the manganese content, due to the displacement character of the transformation of austenite, increase the amount of carbon in solution and leads to precipitation hardening similar to the intermediate transformation activated by cold plasmic deformation. The dispersed structure formed in this case ensures high strength and ductility of the material.Moscow Automobile Factory. Moscow Evening Metallurgical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 47–51, September, 1980.     

The Martensitic Transformation and Strain-Hardening Behavior of Austenitic Steels During Fatigue and Tensile Loading

The tensile and low-cycle fatigue deformation and α′-martensitic transformation behavior of three austenitic steels with varied silicon, aluminum, and nickel levels were characterized using mechanical testing and transmission electron microscopy. Silicon alloying promoted deformation twinning and high work-hardening rates in tension by lowering the stacking fault energy (SFE). Deformation twins and their intersections served as martensite nucleation sites in tension. Martensitic transformation was maximized in the alloy with a low SFE, which increased the alloy capacity to form strain-induced nucleation sites, and low nickel content, which increased the thermodynamic driving force for martensite formation. In fatigue loading, martensite nucleation occurred on localized austenite shear bands composed of dissociated dislocations that form in the cyclically stabilized portion of the fatigue life. The shear bands occurred in all materials irrespective of the SFE. The extent of martensitic transformation in fatigue is apparently dictated more by thermodynamic driving force for transformation and not by SFE. In both tension and fatigue, martensite formation led to strain hardening.     

Cr8Mo2SiV钢二次硬化机理的研究

采用硬度计SEM,EDS,TEM和XRD研究了经深冷处理和未经深冷处理Cr8Mo2SiV钢的回火硬度、残余奥氏体含量和碳化物析出行为.结果表明,Cr8Mo2SiV钢经1030℃淬火后,二次硬化峰值硬度出现在回火温度为520℃.深冷处理能够显著减少残余奥氏体含量,进而提高二次硬化峰温度之前的回火硬度,并使二次硬化峰向低温区移动20℃.在520℃回火处理,Cr8Mo2SiV钢的回火硬度随保温时间的延长而线性降低.Cr8Mo2SiV钢的二次硬化是残余奥氏体的转变和Mo_2C的析出前期共同作用的结果,残余奥氏体的作用更大.Mo_2C的析出前期合金元素Mo和C形成[Mo-C]偏聚团的G.P.区,随回火时间延长,Mo_2C析出并长大,均匀弥散分布于基体中.