动态应变时效对35CrMo钢力学性能的影响

采用慢应变速率拉伸、电子显微镜等现代分析方法,研究了35CrMo钢动态应变时效现象对力学性能的影响.结果表明:在应变量为5％、应变速率为5×10-4s-1的不同温度(293、323、373和473 K)下动态应变时效后的35CrMo钢的伸长率变化不大,但动态应变时效后的抗拉强度均明显增加;35 CrMo钢动态应变时效的最佳温度为373K.35CrMo钢试样在室温下经过动态应变时效处理之后的室温屈服强度明显增加.     

马氏体钢MS1180在高应变速率下的力学性能

汽车在轻量化的同时需要保证安全性能,对材料的动态力学性能进行研究与表征,对汽车车身设计及选材具有很重要的指导意义。本文使用高速拉伸试验机对本钢马氏体钢MS1180进行高应变速率拉伸测试,研究了材料应力与应变速率的关系,通过对比分析不同动态本构模型对材料应变率效应和塑性硬化行为的影响,确认了加权组合方式的Swift-Hockett/Sherby模型在描述材料动态力学性能方面的灵活性和准确性。     

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。     

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.     

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.     

高硅铸钢热处理显微组织和力学性能的实验研究

对高硅铸钢在不同等温淬火温度、时间内的显微组织和力学性能进行了实验研究.结果表明,高硅铸钢在280～360℃范围内等温淬火,可以获得强度、韧性、硬度配合良好的双相组织;试样中残余奥氏体的含碳量及其含量随着等温淬火温度的升高先增大后减小,均在360℃等温淬火时出现最大值;奥氏体化温度和时间为900℃×120 min、等温淬火温度和时间为320℃×120 min时,可以获得较佳的综合力学性能.试验结果可为高硅铸钢在冲击磨损条件下替代高锰钢、低合金钢、奥-贝球铁等提供理论参考依据.     

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。     

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.     

高应变率下热挤压态细晶钨合金的动态力学性能及失效行为

采用快速热挤压技术对细晶93W-4.9Ni-2.1Fe-0.03Y%进行变形强化,研究了高应变率下挤压态细晶钨合金动态力学性能及失效行为。结果表明:在较低应变速率下的挤压态细晶钨合金的屈服强度相近,约2000 MPa;断面上的钨颗粒被严重拉长直至破碎,破碎的细小钨颗粒粘附在软化的粘结相中,随着应变率的增加钨颗粒变形更加明显;剖面观察发现:沿着断裂面的钨颗粒发生了高度的剪切变形,而内部区域则基本没有变形,表现出了剪切局域化迹象。实验结果证明了挤压态细晶钨合金在动态加载条件下的失效方式是绝热剪切失效。     

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。     

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。     

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.     

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.     

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.     

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.     

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。     

高硅铸钢残余奥氏体分布形态及其对力学性能的影响

采用透射电子显微镜(TEM)对高硅铸钢等温淬火热处理后的显微组织以及残余奥氏体分布形态进行了研究,对等温淬火组织中残余奥氏体量进行了测定.结果表明,残余奥氏体呈薄膜状及块状两种分布形态.薄膜状分布的残余奥氏体与贝氏体铁素体间的位向符合K-S关系,对钢的综合力学性能特别是韧性有积极的作用;而呈块状分布的残余奥氏体,由于其机械稳定性差,对钢的各项力学性能有不利的影响.要获得具有优异综合力学性能的高硅铸钢,薄膜状残余奥氏体与块状残余奥氏体体积分数量的比值Vγ-F/Vγ-B要大于1.0.     

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.