Q&P工艺对5CrMnNiMo超高强度钢组织及性能的影响

对5CrMnNiMo超高强度钢进行了淬火-配分(Q&P)处理,利用SEM、电子万能试验机、X射线衍射仪、EBSD等试验手段,探讨了试验钢的显微组织和力学性能随Q&P工艺中等温配分5 min、24 h及非等温配分6 h后的变化规律。结果表明,Q&P处理过程中,显微组织均由马氏体+残留奥氏体+少量粒状碳化物组成,随着等温配分时间的延长,残留奥氏体由片状逐渐转变为块状;等温配分5 min后,获得高达2230 MPa的超高抗拉强度,抗拉强度经等温配分24 h后降低到1360 MPa;塑性变形量由等温配分5 min后的3.92%增加到非等温配分6 h后的14.62%,TRIP效应是塑性变形量增加的主要原因。     

5A06铝合金复杂盒形件等温锻造工艺研究

针对5A06铝合金复杂盒型件,利用有限元分析软件Deform,确定了先预成形后终成形的等温锻造成形工艺方案。并通过逆向补偿方法设计了预成形及终成形模具。在20 MN锻压机上,先将铝合金板材预锻成预制坯,然后再等温终锻。等温锻造工艺中,模具温度为(450±10)℃,5A06铝合金预制坯温度为(465±10)℃,成形时最大挤压力为14000 k N。等温锻造试验表明;Deform有限元分析对等温锻造成形工艺研究具有较强的指导意义,采用先预成形后终锻成形工艺能大大提高锻件成形质量;此外,5A06铝合金等温锻造盒型件相较于机械加工盒型件,抗拉强度Rm提高到350 MPa,伸长率A提高到25%。     

Sn-3.5Ag-0.5Cu/Cu界面的显微结构

研究了热-剪切循环条件下Sn-3．5Ag-0．5Cu钎料／Cu界面的显微结构，分析了界面金属间化合物的生长行为，并与恒温时效后的Sn-3．5Ag-0．5Cu／Cu界面进行了对比。结果表明：恒温时效至100h，Sn-3．5Ag-0．5Cu／Cu界面上已形成Cu6Sn5和Cu3Sn两层金属间化合物；而热-剪切循环至720周Sn-3．5Ag-0．5Cu／Cu界面上只存在Cu6Sn5金属间化合物层，无Cu3Sn层生成，在界面近域的钎料内，颗粒状的Ag3Sn聚集长大成块状；在热-剪切循环和恒温时效过程中，界面金属间化合物的形态初始都为扇贝状，随着时效时间的延长逐渐趋于平缓，最终以层状形式生长。     

Cr5钢过冷奥氏体转变研究

通过膨胀法测试了Cr5钢过冷奥氏体连续及等温转变曲线,根据测得的CCT和TTT曲线对显微组织与硬度进行了研究,为Cr5钢的热处理与应用提供依据。     

5A06铝合金鞍型横梁等温挤压近净成形工艺

针对某5A06铝合金鞍型横梁,设计了等温挤压近净成形试验。通过Deform有限元分析研究了鞍型横梁等温挤压过程中金属流动规律和缺陷产生原因,并进行了毛坯尺寸和热挤压件图的优化。设计了鞍型横梁等温挤压近净成形模具,可实现在普通压力机上加热管加热方式升温、成形后多顶杆同步脱模功能。通过等温挤压近净成形方法制备了长为580 mm、最薄壁厚为4 mm、筋高为8 mm、筋宽为6 mm的薄壁复杂多筋鞍型横梁,该构件90%以上部位尺寸精度可达到±0. 3 mm,其余部位尺寸精度可达±0. 5 mm,抗拉强度达340 MPa,伸长率约为25%。对等温挤压件装配部位进行少量机加,可获得3种不同尺寸的鞍型横梁。     

Thermal stability of Zr_(55)Al_(10)Ni_5Cu_(30)bulk amorphous alloy during continuous heating and isothermal annealing

1　INTRODUCTIONBulkamorphousalloyspossessalongrangedis orderbutshortrangeorderstructure ,whichresem blesthestructureofliquid .Andthereisasupercooledliquidregionbeforecrystallizationofabulkamor phousalloy .Thisuniquestructureresultsinexcellentpropertiessuchashightensilestrength ,highhard ness,highimpactfractureenergy ,highelasticener gy ,highcorrosionresistance ,highviscousflowabilityandgoodsoftmagnetism[13] .Thesynthesisofmetallicglassesinabulkform (withthickness >1mm )wassuccessfullyachi…     

Effects of quenching conditions on crystallization behavior of amorphous Al90Ni5Ce5 alloys

X-ray diffraction and DSC were used to investigate the crystallization behavior of amorphous Al90Ni5Ce5 alloys at different quenching temperatures.All the amorphous Al90Ni5Ce5 alloys quenched at different temperatures crystallize by two stages.The first stage corresponds to FCC Al phase precipitating from the amorphous matrix.The crystallization onset temperature increases with increasing quenching temperature.The quenching temperature also influences the isothermal behaviors.At low quenching temperatures,the FCC Al precipitation is only through grain growth.At high quenching temperatures,the FCC Al precipitation is through growth of quenched-in Al unclei and nucleation and growth of new crystallites.The reason that the crystallization onset temperature varies with quenching temperature is likely as that the quenched-in Al nuclei decreases with increasing temperature.     

Zr_(55)Cu_(30)Ni_5Al_(10)大块金属玻璃的等时和等温晶化(英文)

采用差示扫描量热仪(DSC)和X射线衍射仪(XRD)研究Zr55Cu30Ni5Al10大块金属玻璃的非等温晶化转变动力学和在过冷液相区的等温晶化动力学行为。在非等温过程中,采用不同方法(Kissinger,Flynn-Wall-Ozawa和Augis-Bennett)得到的Zr55Cu30Ni5Al10大块金属玻璃平均激活能彼此之间吻合很好。此外,采用Johnson-Mehl-Avrami(JMA)模型描述Zr55Cu30Ni5Al10大块金属玻璃的等温转变动力学。研究结果表明:Zr55Cu30Ni5Al10大块金属玻璃的Avrami指数n介于2.2和2.9之间,表明其晶化机制主要是扩散控制过程。在等温晶化的过程中,晶核长大主要是三维的长程有序扩散控制的过程,平均激活能为469kJ/mol。     

Prediction of Forming Limit Diagrams for 22MnB5 in Hot Stamping Process

Hot stamping of ultra-high strength steels possesses many superior characteristics over conventional room temperature forming process and is fairly attractive in improving strength and reducing weight of vehicle body product. However, the mechanical and failure behavior of hot stamping boron steel 22MnB5 are both strongly affected by strain hardening, temperature, strain rate, and microstructure. In this paper, the material yield and flow behavior of 22MnB5 within the temperature and strain rate range of hot stamping are described by an advanced anisotropic yield criterion combined with two different hardening laws. The elevated temperature forming limit diagram (ET-FLD) is constructed using the M-K theoretical analysis. The developed model was validated by comparing our predicted result with experimental data in the literature under isothermal conditions. Based on the verified model, the influence of temperature and strain rate on the forming limit curve for 22MnB5 steel under equilibrium isothermal condition are discussed. Furthermore, the transient forming limit diagram is developed by performing a transient forming process simulation under non-isothermal transient condition.     

大型5CrNiMo钢锤锻模具工艺改进

分析了大型锤锻5CrNiMo钢模具失效的原因.可知,在较大应力作用下,模具钢中的粗大疏松组织和非金属夹杂物等内部缺陷部位容易产生裂纹并扩展.对大型锤锻模具工艺进行改进,在原等温退火工艺之前,进行正火细化模具毛坯晶粒并且消除其网状、链状碳化物,再优化调质工艺可以减少热处理应力和避免模具发生裂纹.     

Oxidation Behavior of Nanostructured Ni-5Al Coating. A case Study on Monophase Coatings

Protection of Metals and Physical Chemistry of Surfaces - Oxidation behavior of nanostructured Ni-5Al HVOF coatings was studied. For this purpose, isothermal oxidation of the free standing coatings...     

5CrNiMoV钢的奥氏体化动力学预测

利用DIL-805ADT动态热膨胀相变仪测定5CrNiMoV热作模具钢在不同加热速率下的膨胀量并对膨胀曲线数据进行分析,运用Kissinger方法拟合出了非等温扩散相变动力学Johnson-Mehl-Avrami(J-M-A)模型中的奥氏体化相变激活能Q、相变参数n和lnk₀,建立5CrNiMoV钢奥氏体化动力学模型。该模型计算所得的奥氏体转变量与试验测量结果相吻合,可用于预测等温奥氏体化动力学曲线和设计5CrNiMoV钢的奥氏体化工艺过程。     

配分工艺对5CrMnNiMo超高强度钢摩擦磨损性能的影响

利用摩擦磨损试验机在载荷50 N,滑动速度0.5 m/s,干摩擦磨损条件下对5CrMnNiMo超高强度钢进行磨损行为研究。采用SEM、EDS、XRD、EBSD等手段探讨了不同配分工艺对其耐磨性的影响规律。结果表明,配分时间较短(等温配分5 min)时耐磨性受硬度控制,磨损率低;随着配分时间延长为6 h(非等温配分)和24 h(等温配分),硬度由800 HV0.2降低到460 HV0.2和390 HV0.2,磨损率略有升高,磨损机理由以磨粒磨损+氧化磨损为主、黏着磨损为辅的方式转变为以黏着磨损为主、磨粒磨损为辅。长时配分促使奥氏体含量增加,在摩擦磨损过程中产生更强的TRIP效应,促使耐磨性增强。     

18MnD5钢动态再结晶模型研究

利用TMTS热物理模拟机对18MnD5钢试样进行等温恒应变速率热压缩实验,获得材料流变应力和微观组织演变规律。通过分析Zener-Hollomon参数与峰值应变、稳态应变、发生50%动态再结晶时的应变及动态再结晶晶粒尺寸之间的关系,对实验结果进行修正,排除误差较大的实验数据。采用修正后的数据建立高精度的18MnD5钢动态再结晶模型,并利用Deform软件对18MnD5钢进行微观组织演变的模拟分析。     

改进型4Cr5Mo2MnV1Si压铸模块钢的球化处理

改进型4Cr5Mo2MnV1Si压铸模块钢采用传统“余热退火+正火+等温球化退火”工艺球化处理后,组织未达到技术要求,对其传统球化处理工艺做了改进,并对改进工艺处理试样的组织、硬度进行检测。结果表明,试验钢余热退火+正火+等温球化退火后,再经1010℃保温0.5 h炉冷至不同温度(820、790和760℃)保温1 h空冷处理后,显微组织均呈板条马氏体形态,基体上均匀弥散分布有碳化物颗粒,但硬度均高于400 HBW,未达到硬度小于240 HBW球化组织的要求。而经1010℃保温0.5 h空冷至室温,再820、790和760℃保温1 h回火空冷处理后,组织均为等轴铁素体上均匀分布着质点状碳化物,硬度分别为321、235和245 HBW,其中790℃回火效果最好,球化组织级别达到GB3,硬度小于240 HBW。因此,采用余热退火+正火+高温回火(790℃)代替余热退火+正火+等温球化退火可实现改进型4Cr5Mo2MnV1Si压铸模块钢的锻后球化处理。     

Isothermal compression behavior and constitutive modeling of Ti-5Al-5Mo-5V-1Cr-1Fe alloy

Hot compression behavior of Ti-5Al-5Mo-5V-1Cr-1Fe alloy with an equiaxed (α+β) starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain–stress data with temperature correction, constitutive models with a high accuracy were developed and processing maps were established. Strain inhomogeneity at different locations in the compressed sample is reduced by raising temperature, leading to a uniform distribution of α phases. For the temperature range of 800–840 °C with a strain rate of 10 s^?1, the transformed volume fraction of α phase increases and the average grain size of α phase decreases slightly with increasing the temperature, indicating co-existence of dynamic recovery and dynamic recrystallization. Flow localization and faint β grain boundaries are observed at the strain rate of 10 s^?1 in the temperature range of 860–900 °C. The processing map analysis shows that hot working of Ti-5Al-5Mo-5V-1Cr-1Fe alloy should be conducted with the strain rate lower than 0.01 s^?1 to extend its workability.     

The reactive-element effect in the high-temperature oxidation of Fe-23Cr-5Al commercial alloys

The effect of yttrium and hafnium additions on high-temperature oxidation resistance of modified Fe-23Cr-5Al commercial, heat-resistant alloys was studied. The oxidation resistance was evaluated by the use of accelerated-life tests and isothermal oxidation for wires and flat samples, respectively. A solgel method of modification of the surface properties of ready-made heating elements was examined. The effect of several sol-gel coatings on the alloy oxidation behavior in the accelerated-life test was studied.     

Zr57Cu15.4Ni12.6Al10Nb5块体非晶合金晶化行为研究

用示差扫描量热仪（DSC）研究了Zr57Cu15.4Ni12.6Al10Nb5块体非晶合金的匀速升温晶化与等温晶化的晶化行为。在匀速升温晶化方式下，用Kissinger法与Ozawa法获得了块体非晶合金的激活能，对第一晶化峰分别为320．5kJ／mol和316．6kJ／mol，对第二晶化峰分别为324．5kJ／mol和320．5kJ／mol。该非晶合金的晶化表现出明显的动力学效应。在等温晶化方式下，用Johnson-Mehl-Avrami方程获得了晶化的Avrami指数为1．61，表明非晶合金的晶化受原子扩散控制。     

Microstructural evolutions of a Cu75-Fe5-Ni20 alloy depending on the isothermal annealing temperatures

The microstructures formed in a Cu₇₅-Fe₅-Ni₂₀ alloy on isothermal annealing at 1073 K were investigated by means of transmission electron microscopy (TEM) and the EELS element mapping technique, to compare with the precipitation phenomena occurring at 873 K. Cubic and rod precipitates were simultaneously formed in the copper matrix in the initial stage of annealing at 1073 K. This feature shows a sharp contrast to the feature observed at 873 K, since only cubic precipitates were observed in the specimens isothermally aged at lower temperatures. The cubic precipitates tend to stretch their shapes along one of the 〈100〉 directions of the Cu matrix and to have rectangular shapes in the late stage of the annealing at both temperatures. This tendency was, however, more clearly observed in the specimen receiving the isothermal annealing at 1073 K.     

Microstructural evolution behavior of Mg–5Si–1Al alloy modified with Sr–Sb during isothermal heat treatment

The microstructural evolution behavior of Mg–5Si–1Al alloys modified with Sr–Sb during isothermal heat treatment was investigated in the present study. Although the morphology of eutectic Mg₂Si phase varied with isothermal holding temperature increasing from 620 to 670 °C, no spheridization occurred for primary Mg₂Si polyhedrons in Sr–Sb-modified alloy even when the temperature reaches 660 or 670 °C. Such an abnormal phenomenon of primary Mg₂Si, during partial remelting isothermal treatment, might be ascribed to both the spheridization restriction effect caused by incorporation of Sb in Mg₂Si and stability of octahedral primary Mg₂Si crystals faced by {1 1 1} planes.