汽车排气管用Nb-Ti铁素体不锈钢在高温时效过程中的力学性能变化

对含Nb-Ti和铌铁素体不锈钢进行高温时效和固溶处理,通过高温拉伸试验研究其高温力学性能变化。结果表明,随着时效时间的延长,铌钢的高温屈服强度下降很快,而Nb-Ti钢的高温屈服强度并没发生较大变化。     

The Effect of Dynamic Strain Aging on Subsequent Mechanical Properties of Dual-Phase Steels

Dual-phase (DP) steels with different martensite contents were produced by subjecting a low carbon steel to various heat treatment cycles. In order to investigate the effect of dynamic strain aging (DSA) on mechanical properties, tensile specimens were deformed 3% at 300 °C. Room temperature tensile tests of specimens which deformed at 300 °C showed that both yield and ultimate tensile strengths increased, while total elongation decreased. The fatigue limit increased after pre-strain in the DSA temperature range. The effects of martensite volume fraction on mechanical properties were discussed.     

低焊接裂纹敏感性高能量焊接用钢的应变时效行为

研制了一种低焊接裂纹敏感性高能量输入焊接用低合金高强钢,并研究了其冷应变时效行为.结果表明,该钢经2.5%及5%拉伸冷应变和应变时效后在常温及-40℃冲击吸收功分别高于100 J和47 J,与基材的冲击吸收功相近,试验钢时效脆性倾向不显著.金相组织观察显示,2.5%及5%拉伸冷应变试样中亚晶粒发生了塑性应变,原奥氏体晶粒未发生明显应变.     

超高应变塑性变形钢丝的力学性能特性

根据损伤力学的基本原理，利用测量弹性模量和观察金相的方法，研究了在拉拔应力状态下，随变形量的不断增大，材料的损伤特性。结果表明，当应变量达到一定程度时，在夹杂物周围、珠光体和铁素体边界上首先形成空洞，即产生损伤。随着应变量的不断增大，空洞数量逐渐增加，材料损伤程度加剧，并得出了材料损伤程度随应变量增大的变化规律。     

应变率对高强度TRIP力学性能的影响

研究了不同应变率(10-4～10-2 s-1)时高强度TRIP钢的力学性能。结果表明,随应变率的增加,抗拉强度与屈服强度总体呈上升趋势,而断裂伸长率及强塑积单调下降。在变形初始阶段(ε0.01),应变率高的实验钢n值较大。随变形量的增加,n值不断下降,且应变率高实验钢的n值下降较快。另得出,应变率越高,初期残余奥氏体向马氏体转变越快。     

非金属夹杂物对等温淬火高硅铸钢力学性能的影响

钢中非金属夹杂物对材料力学性能的影响十分显著。本文利用图像分析技术 ,系统研究了非金属夹杂物对等温淬火高硅铸钢力学性能的影响。试验结果表明 :高硅铸钢的夹杂物主要为Si、Cr、Fe的氧化物 ;夹杂物平均尺寸、夹杂物面积百分数、夹杂物平均间距等参数均影响材料的力学性能 ;夹杂物平均尺寸大于 15μm、夹杂物面积百分数大于1%、夹杂物平均间距小于 2 5μm时 ,就会极大地影响高硅铸钢的抗拉强度和冲击韧性。     

时效处理对高碳钢盘条性能的影响

研究了时效处理时间对SWRH72B和SWRH82B高碳钢盘条抗拉强度和断面收缩率的影响规律,测量了材料中氢含量的变化,用扫描电镜分析了高碳钢盘条拉伸断口形貌的变化.结果表明,经过时效处理后,SWRH72B和SWRH82B高碳钢盘条的抗拉强度变化不大,但断面收缩率提高50%以上;随着时效时间的延长,盘条中氢含量逐渐降低;未经充分时效处理的拉伸断口上存在白圈,时效处理后白圈消失.     

硅铬系合金铸钢的组织与性能

研究了硅铬系合金铸钢在不同热处理工艺条件下的组织及力学性能.铸钢的铸态组织由片状马氏体和少量的残余奥氏体以及沿晶界呈连续网状分布的碳化物组成,经过空淬和回火处理之后得到回火马氏体和呈粒状分布的合金碳化物.硅铬系合金铸钢在1 000℃奥氏体化,200℃回火时可获得最佳性能.研究表明,经过空淬和回火处理的硅铬系合金铸钢具有很高硬度和一定的冲击韧性,具有很好的耐冲击磨损性能,适合于对冲击韧性要求不是很高,但对耐磨性要求比较高的场合.     

高应变速率下TC11钛合金动态剪切行为与性能

采用分离式霍普金森压杆（Hopkinson Bar）装置系统,对TC11钛合金进行室温高应变速率（700-2100s^-1）动态剪切试验,通过光学显微镜、显微硬度分析仪、扫描电镜研究了TC11钛合金动态剪切行为、绝热剪切带微观组织与性能。结果表明：TC11钛合金随应变速率的提高绝热剪切敏感性增加;绝热剪切带由过渡区域的变形拉长组织和中间部位的细小晶粒组织组成,具有清晰的剪切变形流线,宽度约为10μm;绝热剪切带内的显微硬度值高于基体组织,是,由应变速率强化和应变强化与热软化相互作用的结果。     

Effect of Dynamic Change in Strain Rate on Mechanical and Stress Corrosion Cracking Behavior of a Mild Steel

The current work analyzes the effect of the dynamic change in strain rate during tensile loading of a mild steel on its mechanical and stress corrosion behavior in 3.5 wt.% NaCl solution. The sample experiences high strain rate (10^?2 s^?1) up to 10, 15 and 20% of total deformation and then very low strain rate of 10^?6 s^?1 till fracture without any unloading in between. The behavioral characteristics of the steel under these circumstances are found to be different from that exhibited during complete loading till fracture both at high and slow strain rates separately. Total strain increases with the increase in the strain at which change in strain rate happens, and this is attributed to the generation of large number of dislocations at higher strain rate and subsequently release of dislocation at low strain rate during change over due to more time available for dynamic recovery. This observation is common for both in air and corrosive environment. One unique observation in this study is the higher total strain and lower strength observed during dynamic change in strain rate in the corrosive environment compared to that in air, which is attributed to the hydrogen-induced plasticity mechanism.     

Aging Precipitation Behavior and Mechanical Properties of Inconel 617 Superalloy

Aging precipitation behavior and mechanical properties of Inconel 617 superalloy aged at 760 ℃ for up to 10000 h were investigated. The results showed that the precipitates of the aged alloy are M23C6 and M6C carbides and γ phase. The carbide particles precipitated both at the grain boundaries and within grains, and the γ phase particles were situated at intragranular sites in the process of aging. The carbide particles were discontinuously dispersed at grain boundaries after aging for 3000 h, while after aged for 5000 h the carbide particles are merged. The precipitates inside grains remained stable even after aging for 10000 h. The hardness was increased for the alloy aged for 300 h up to 3000 h, which was resulted primarily from the precipitation of carbides as discrete particles both at the grain boundaries and inside grains. Small quantity γ precipitates were formed inside grains, to some extent, which contributed to an enhanced hardness. However, a decrease of the hardness was observed after aging for 5000 h. A significant drop in toughness of the alloy aged for 300 h was attributed to the reduction of the bonding interface strength when carbides precipitated at grain boundaries. Thereafter, the toughness decreased slowly with the prolonged aging time. The high temperature tensile properties of the aged alloy are rather stable even aged for 300-3000 h.     

Modeling the High Temperature Flow Behavior and Dynamic Recrystallization Kinetics of a Medium Carbon Microalloyed Steel

In this study, the hot deformation behavior of a medium carbon microalloyed steel was investigated. The hot compression test was conducted in the temperature range of 1000-1200 °C under strain rates of 0.01, 0.1 and 1 s^?1. It has been observed that the flow stress increases with a decrease in temperature and/or an increase in strain rate. Furthermore, dynamic recrystallization (DRX) is found to be the main flow softening mechanism in almost all deformation conditions. Material parameters of the constitutive equations are found to be strain dependent. Their relationship with strain is identified by a fourth order polynomial fit. Then, a constitutive model is developed to predict the flow stress of the material incorporating the strain softening effect. The accuracy of the proposed model for the flow stress is evaluated by applying the absolute average error method. The result of 6.08% indicates a good agreement between predicted and experimental data. Moreover, the critical characteristics of DRX are extracted from the stress-strain curves at different deformation conditions. It is found that by increasing the strain rate at a constant temperature or decreasing deformation temperature under a constant strain rate, the recrystallization curve shifts to the higher strains. The kinetics of DRX increases with increasing deformation temperature or strain rate.     

316L奥氏体不锈钢高温拉伸时的动态应变时效

在300～700℃,以应变速率为2×10-4 s-1对316L不锈钢进行拉伸试验,探索其中的动态应变时效现象及其规律.结果表明,316L奥氏体不锈钢在动态应变时效温度区间并没有出现屈服应力平台,在450～700℃既有正常的Portevien-Le Chatelier effect (PLC)效应,也有反PLC效应;锯齿形成的有效激活能为254k J/mol;扩散着Cr等置换型溶质原子与运动位错之间的交互作用使材料出现动态应变时效,导致锯齿流动行为.     

高强韧性炮钢的组织和力学性能

研究了合金化元素对新型高强韧炮钢的热处理制度、显微组织和力学性能的影响。结果发现,钢中形成的Nb（C,N）特殊碳化物在1050℃以下能有效控制钢的晶粒长大;在回火过程中,随回火温度的提高,M2C碳化物逐渐增多,在640℃达到强韧性最佳配合。经1000℃淬火并640℃回火后试验钢的吼达到1260MPa,σo．00。达到870MPa,冲击韧度达到45J／cm^2并对其强韧性机理进行了初步分析。     

H68黄铜动态应变时效后的组织与性能

在4.76×10-4s-1的应变速率、100K～673K 的温度范围内进行了系列温度拉伸试验、恒应力时效试验以及对动态应变时效(DSA)预处理后微观组织的观察,研究了DSA对H68黄铜组织和性能的影响.结果表明,H68黄铜在250K～600K的温度范围内会出现DSA现象;在DSA温区内,出现屈服应力平台及加工硬化速率峰值.在动态应变时效过程中发生的运动位错与溶质原子之间的交互作用使材料的位错组态发生变化,在相同的预应变量下,随着DSA预处理的温度升高,材料的位错密度提高,形成更复杂、更稳定的位错组态.     

热处理工艺对高强钢拉杆的组织与力学性能的影响

采用连续感应淬回火技术对20MnSi、20MnSiV和45钢拉杆进行淬火和回火实验,研究了其组织和性能变化。结果表明,钒元素能够降低回火温度对钢拉杆抗拉强度与屈服强度的影响。淬回火处理的45钢拉杆的组织为回火索氏体+铁素体,具有更好的冲击韧度。     

织构对冷轧无取向硅钢板磁时效的影响

研究了含碳量约(20~30)×10-6的50W 800冷轧无取向硅钢板的织构与磁时效行为的关系。200℃×24 h的磁时效试验结果表明,α-Fe{100}面的平均弹性模量最低,且与渗碳体的弹性模量接近,因此渗碳体易沿{100}面片状析出,造成磁时效,使硅钢板的铁损升高。磁化时180°磁畴畴壁的驱动力与硅钢板织构有密切关系,其100平行于外磁场方向的织构有利于减小磁时效导致的铁损增幅,降低钢板的磁时效效应。     

连续退火对汽车用高硅双相钢组织及力学性能的影响

通过研究汽车用高Si双相钢在连续退火过程中组织及力学性能的变化,重点分析了退火温度对双相钢性能的影响规律。结果表明,试验钢在连续退火后,铁素体晶界上出现均匀分布的岛状马氏体和粒状残余奥氏体组织;随着退火温度的升高,试验钢的抗拉强度先升高后降低,当退火温度为785℃时,钢的综合力学性能较高。     

TRIP800钢在等温时效过程中组织及力学性能的研究

利用扫描电镜、透射电镜、XRD和力学性能测试,研究含钒TRIP800钢板在等温时效过程中的组织和力学性能变化。结果表明,试验钢中残余奥氏体含量受到贝氏体等温处理温度的影响,当处理温度为370⁴10℃时,残余奥氏体含碳量随温度的升高而升高,但当温度高于410℃时,含量下降;当处理温度低于410℃时,试验钢的伸长率、强塑积和屈服强度在贝氏体随着温度的升高而上升,在410℃时力学性能达到最佳;钒元素的添加增加钢中碳化钒的析出量,提高钢的力学性能;通过和双相钢相比,TRIP钢均匀变形能力更好。     

42CrMoVNb细晶高强度钢的力学行为

通过快速循环热处理和改变奥氏体化温度的方法获得不同的原奥氏体晶粒尺寸,研究了晶粒尺寸特别是超细晶粒尺寸对中碳42CrMoVNb钢力学行为的影响。结果表明,晶粒从8μm细化到4μm时,实验钢的强度提高、塑性下降,除弹性变形能外,单轴拉伸的形变强化指数、均匀塑性变形能、裂纹扩展能和总能量均有所降低;当晶粒进一步细化到2μm时,强度不再提高。随着回火温度的升高,强度随晶粒细化而提高的幅度减小。晶粒细化能够明显地提高实验钢冲击断裂时所吸收的能量,降低韧脆转变温度。