共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
3.
4.
《Baosteel Technical Research》2012,6(1):61-64
Thermal simulation tests were conducted at different deformation temperatures and degrees by a Gleeble simulator.The results show that the alloy has higher resistance to deformation;with an increase of the deformation temperature,the alloy's flow stress and maximum value decrease;with an increase of the deformation degree,both the initial recrystallization temperature and the complete recrystallization temperature decrease sharply.When the deformation degree reaches 30%,60% and 80%,the initial recrystallization temperature is around 950℃,850℃ and 800℃,the complete recrystallization temperature is around 1 100℃,1 050℃ and 1 000℃ respectively.When the deformation temperature is higher than 1100℃,the deformation degree increases and the re-crystalized grains are significantly refined.The forging process parameters were established according to the regular pattern mentioned above.The microstructure of the bar forged in this pattern is uniform and the result is satisfying. 相似文献
5.
通过一系列实验研究了Monel K-500合金的冲击韧性。结果表明,合金经550~650℃时效后其冲击断口呈沿晶形貌;在750~850℃时效时,其冲击韧性与强度呈正相关关系。根据对合金在不同热处理状态的析出相形态及分布的研究,揭示了形成这些现象的原因。合金在550~650℃时效时,在晶内析出的γ’相呈球状均匀分布,而在部分晶界附近的γ’相呈条棒状或排成帘状垂直于晶界分布,由此导致时效态合金在断裂时,裂纹沿晶界扩展。在750~850℃时效会导致合金形成大量沿晶界网状分布的二次MC相,从而降低合金的冲击韧性。 相似文献
6.
利用Gleeble热模拟试验机对Monel K-500合金进行了不同变形温度、不同变形量的热模拟试验。结果表明,合金变形抗力大,随着温度的升高,合金的流变应力及其最大值降低。随变形量增大,初始再结晶温度和完全再结晶温度均明显降低,当变形量分别为30%、60%、80%时,其初始再结晶的变形温度分别为950、850、800℃左右;其完全动态再结晶的变形温度分别为1 100、1 050和1 000℃左右。当变形温度高于1 100℃,随变形量增大,再结晶晶粒显著细化。根据上述规律制订出了该合金的锻造工艺,所锻造的该合金棒材组织均匀,效果良好。 相似文献
7.
Environment-Assisted Cracking in Custom 465 Stainless Steel 总被引:1,自引:0,他引:1
E. U. Lee R. Goswami M. Jones A. K. Vasudevan 《Metallurgical and Materials Transactions A》2011,42(2):415-423
The influence of cold work and aging on the environment-assisted cracking (EAC) behavior and mechanical properties of Custom
465 stainless steel (SS) was studied. Four sets of specimens were made and tested. All specimens were initially solution annealed,
rapidly cooled, and refrigerated (SAR condition). The first specimen set was steel in the SAR condition. The second specimen
set was aged to the H1000 condition. The third specimen set was 60 pct cold worked, and the fourth specimen set was 60 pct
cold worked and aged at temperatures ranging from 755 K to 825 K (482 °C to 552 °C) for 4 hours in air. The specimens were
subsequently subjected to EAC and mechanical testing. The EAC testing was conducted, using the rising step load (RSL) technique,
in aqueous solutions of NaCl of pH 7.3 with concentrations ranging from 0.0035 to 3.5 pct at room temperature. The microstructure,
dislocation substructure, and crack paths, resulting from the cold work, aging, or subsequent EAC testing, were examined by
optical microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The aging of the cold-worked
specimens induced carbide precipitation within the martensite lath, but not at the lath or packet boundaries. In the aged
specimens, as aging temperature rose, the threshold stress intensity for EAC (KIEAC), elongation, and fracture toughness increased, but the strength and hardness decreased. The KIEAC also decreased with increasing yield strength and NaCl concentration. In the SAR and H1000 specimens, the EAC propagated
along the prior austenite grain boundary, while in the cold-worked and cold-worked and aged specimens, the EAC propagated
along the martensite lath, and its packet and prior austenite grain boundaries. The controlling mechanism for the observed
EAC was identified to be hydrogen embrittlement. 相似文献
8.
9.
蒙乃尔是一种镍铜合金,现代工业中常在其中添加铝以提为高性能。本实验研究用铬天青S光度法,以Zn-EDTA为掩蔽剂,HAC-NaAC为缓冲溶液测定蒙乃尔K-500中的铝量。 相似文献
10.
R. K. Singh Raman Muhammed Khalissi Shahin Khoddam 《Metallurgical and Materials Transactions A》2014,45(4):1979-1995
This article presents the study of the environment-assisted cracking (EAC) of twinning induced plasticity (TWIP) steels that possess remarkable combination of strength and ductility. EAC of a high-manganese TWIP steel was investigated, using aqueous solutions of different pH, which provided a mechanistic insight into the combined role of the localized deformation due to twinning and the electrochemical characteristic of the steel. Slow strain rate testing in inert environment as well as in acidic, neutral and alkaline solutions, and the fractography of the failed specimens have suggested a profound role of twinning in EAC crack propagation. 相似文献
11.
12.
The Influence of Grain Boundary Phosphorus Concentration on Liquid Metal and Hydrogen Embrittlement of Monel 400 总被引:1,自引:0,他引:1
A. W. Funkenbusch L. A. Heldt D. F. Stein 《Metallurgical and Materials Transactions A》1982,13(4):611-618
The susceptibility of Monel 400® to embrittlement by mercury and by hydrogen was measured as affected by thermal treatment. Specimens were annealed at 900°C and either quenched or furnace cooled. Auger analysis revealed phosphorus segregated to the grain boundaries; furnace cooling causes the boundary concentration to be about twice that of the quenched material. Tensile tests were conducted with specimens (1) in air, (2) coated with mercury, or (3) cathodically precharged with hydrogen. Fractures in air were completely ductile, and ductility was not affected by thermal treatment. Fractures of mercury-coated and hydrogen-charged samples were brittle and intergranular; elongation to fracture increased significantly with increasing concentration of grain boundary phosphorus. The results are discussed in terms of additive and interactive mechanisms. 相似文献
13.
A three-dimensional (3D) hypoelastic material model for modeling material properties of cracked reinforced concrete is proposed. Material properties of multidirectionally cracked reinforced concrete are represented by the material properties of intact concrete and a number of uniaxially cracked concrete with their coupling solids. Cracking effects due to multiple nonorthogonal cracks are traced in each uniaxially cracked concrete. Tension softening and aggregate interlock occurring at the crack interface as well as tension stiffening and compression softening initiated in concrete between cracks due to multiple nonorthogonal cracks are all incorporated explicitly. RC panels under in-plane loading and RC slab under pure torsion have been analyzed. The developed 3D hypoelastic material model has been proved to be efficient and effective in modeling the material behaviors of cracked reinforced concrete in shell-type RC structures. The deformational response, the ultimate strength, and failure mode can be captured reasonably well. 相似文献
14.
The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed. 相似文献
15.
铌对氢化锆裂纹行为和氢含量的影响 总被引:1,自引:0,他引:1
氢化锫是一种理想的固体中子慢化材料,尤其适用于空间核电源的反应堆,但是高氢含量的氢化锫在制备过程中很容易形成裂纹.Nb是氢化锆中的主要添加元素,对氢化锆的裂纹形成和氢含量有一定影响,这是由Nb在氢化锆中的存在形式决定的,对此进行了研究.结果表明,在吸氢充分的情况下,不同Nb含量的Zr - Nb合金氢化后产物的主要组成都是ZrH2,ZrH1.950和ZrH1.801的ε相氢化锆混合物,Nb的添加对氢化锫的晶格常数和晶胞大小影响不大.Nb改善了氢化锫的多缺陷状态,减少了氢富集的位置,从而起到抑制裂纹产生的作用.常压下,Nb的添加会影响合金的最大吸氢量,尤其当Nb含量在10%以上时,会生成低氢含量的NbHx固溶体,影响锆合金的整体吸氢量.Nb在氢化锆中的固溶度较小,Nb含量较低时,大部分Nb以白色含H锫铌固溶体小颗粒的形式弥散分布在氢化锫表面. 相似文献
16.
Greger L. Pioszak Richard P. Gangloff 《Metallurgical and Materials Transactions A》2017,48(9):4025-4045
Martensitic steels (Aermet®100, Ferrium®M54?, Ferrium®S53®, and experimental CrNiMoWV at ultra-high yield strength of 1550 to 1725 MPa) similarly resist hydrogen environment assisted cracking (HEAC) in aqueous NaCl. Cracking is transgranular, ascribed to increased steel purity and rare earth addition compared to intergranular HEAC in highly susceptible 300M. Nano-scale precipitates ((Mo,Cr)2C and (W,V)C) reduce H diffusivity and the K-independent Stage II growth rate by 2 to 3 orders of magnitude compared to 300M. However, threshold K TH is similarly low (8 to 15 MPa√m) for each steel at highly cathodic and open circuit potentials. Transgranular HEAC likely occurs along martensite packet and {110}α′-block interfaces, speculatively governed by localized plasticity and H decohesion. Martensitic transformation produces coincident site lattice interfaces; however, a connected random boundary network persists in 3D to negate interface engineering. The modern steels are near-immune to HEAC when mildly cathodically polarized, attributed to minimal crack tip H production and uptake. Neither reduced Co and Ni in M54 and CrNiMoWV nor increased Cr in S53 broadly degrade HEAC resistance compared to baseline AM100. The latter suggests that crack passivity dominates acidification to widen the polarization window for HEAC resistance. Decohesion models predict the applied potential dependencies of K TH and da/dt II with a single-adjustable parameter, affirming the importance of steel purity and trap sensitive H diffusivity. 相似文献
17.
M.M. HallJr 《Metallurgical and Materials Transactions A》2011,42(2):304-318
Fitness-for-service evaluations of engineered components that are subject to environment assisted cracking (EAC) often require
analyses of potentially large crack extensions through regions of variable stress intensity. However, there are few EAC data
and models that directly address the effects of variable stress intensity factor on EAC crack growth. The model developed
here is used to evaluate stress corrosion cracking (SCC) data that were obtained on a high-strength beta-titanium alloy under
conditions of variable crack mouth opening displacement (CMOD) rate. SCC of this Ti alloy in ambient temperature, near-neutral
NaCl aqueous solution is thought to be due to hydrogen environment assisted cracking (HEAC). As the model equations developed
here do not admit to a closed form solution for crack velocity as a function of applied stress intensity factor, K, a semiquantitative graphical solution is used to rationalize the crack growth data. The analyses support a previous suggestion
that the observed crack growth rate behavior can be attributed to the effect of crack tip strain rate on rates of mechanical
disruption and repair of an otherwise protective crack tip oxide film. Model elements introduced here to HEAC modeling include
(1) an expression relating corrosion-active surface area to crack tip strain rate and repassivation rate, (2) an expression
relating the critical grain boundary hydrogen to the applied stress intensity factor, and (3) an expression relating CTSR
to both applied and crack advance strain rate components. Intergranular crack advance is modeled assuming diffusive segregation
of corrosion-generated hydrogen to grain boundary trap sites causing embrittlement of the fracture process zone (FPZ). The
model equations developed here provide a quantitative basis for understanding the physical significance of K-variation effects and, with additional development, will provide an engineering tool for analysis of crack growth in a variable
K field. 相似文献
18.
采用阴极充H、恒载荷拉伸和电化学H渗透等试验方法,研究了超高强度钢22MnB5Nb的H扩散行为及氢致滞后开裂性能,并与常用热冲压钢22MnB5进行了对比。结果表明,H在22MnB5Nb钢中的扩散系数为3.02×10-7 cm2/s,显著低于22MnB5钢;与22MnB5钢相比,22MnB5Nb钢具有较好的耐氢致滞后开裂性能;这是由于22MnB5Nb钢晶粒较细小,增加了晶界的有效面积,使H陷阱分布更均匀,进而抑制H向裂纹尖端扩展,避免了局部H的富集。 相似文献
19.
Stress corrosion cracking (SCC) is commonly observed to form a colony of closely spaced multiple cracks. Four stages of SCC colony evolution are discussed. The first is the colony initiation stage (CIS), which is associated with formation of corrosion pits randomly distributed over a certain domain of the surface exposed to an aggressive environment. Electrochemical processes play a leading role in CIS. The individual crack growth (ICG) driven by a combination of mechanical stresses and electrochemical processes constitutes the second stage. At the end of the second stage, the individual cracks reach certain proximity of one another resulting in much crack interaction. This becomes a transition to the third, strong crack interaction and clusters formation, stage. Cluster growth and individual crack or a cluster instability leading to the ultimate failure constitute the final, fourth stage of the SCC evolution process. In this article, we present observations and a general approach to modeling the first two stages of SCC, i.e., CIS and ICG, that together constitute the major part of the total lifetime of an engineering structure serving under SCC conditions. A computer simulation of individual SC crack growth is developed and compared with a large set of SCC observation data. 相似文献