共查询到20条相似文献,搜索用时 93 毫秒
2.
3.
4.
5.
Cu-Zn 合金贝氏体相变热力学 总被引:1,自引:0,他引:1
对 Cu-40at.-%Zn 合金贝氏体相变温度范围内各种可能相变的驱动力进行了计算。结果表明,由于在这温度范围内存在β→β′有序相变,因而相变驱动力ΔG~(β′→α′)及ΔG~(β′→β_1′+α)随温度下降反而增大,且ΔG~(β′→α′)>0,ΔG~(β′→β_1′+α)<0;而且各成分合金β′及α′两相平衡温度 T_0,远低于 B_s 实验值,所以贝氏体相变只能按β′→β_1′+α扩散型相变进行。 相似文献
6.
铁基合金的贝氏体基元及其生长演化 总被引:1,自引:0,他引:1
用透射电镜研究了 Fe-C-Mo 和 Fe-C-Si-Mn 合金中温转变早期产物的组织形态,发现在整个中温转变范围非平衡先析型转变都是按贝氏体铁素体相变基元形成及其扩散生长演化方式进行,说明经生长演化一些时间后的基元难于作为判断贝氏体形核机制的形态学依据。从基元生长演化进程区分了低碳贝氏体和板条马氏体。 相似文献
7.
8.
9.
10.
11.
12.
针对贝氏体研究中的超级贝氏体组织,设计了试验用钢70MnSi2CrMo,经低温等温处理,获得贝氏体铁素体+残余奥氏体的组织,利用X射线衍射XRD、扫描电子显微镜SEM、透射电子显微镜TEM等仪器对其进行相组成和形态的检测分析.结果表明:在马氏体转变开始温度Ms点稍上的中低温区等温处理,贝氏体铁素体沿γ相晶界转变,无碳化物析出;α相转变排碳导致成分起伏,α/γ交界处过冷奥氏体稳定性增加,难以转变成马氏体;贝氏体铁素体的转变特征、过饱和的碳浓度、高密度位错、以及纳米尺寸相界面和亚结构等,影响着超级贝氏体钢的力学性能. 相似文献
13.
14.
B. Avishan S. Yazdani F. G. Caballero T. S. Wang C. Garcia-Mateo 《Materials Science & Technology》2015,31(12):1508-1520
Recently, valuable combinations of mechanical properties with strength of 1.9 GPa accompanied by very decent ductility of 19% and toughness of 31 J, have been achieved in a set of nanostructured bainitic steels. However, it is necessary to elucidate the significance of various microstructural features responsible of that extraordinary mechanical response in more detail. Thus, using two steels, with different Mn, Ni and V contents, and changing the nanostructured bainite isothermal transformation temperatures (200–300°C), has led to a plethora of subtle and essential microstructural variations, necessary to explain how the mechanical response of nanostructured bainite is attained. 相似文献
15.
The external forces method is a numerical method for K calculation based on the finite element method. It uses the work of
the external forces W for the calculation of the energy release rate and is particularly advantageous when that forces are
applied far from the crack front. The method was applied to a corner crack geometry with the objective of studying its accuracy.
Good results were obtained for a wide range of virtual crack displacements (0.03% < Δa/a < 6%) considering 4 values of W along
with a polynomial regression of order 3. For that choice of parameters the inaccuracy of K is mainly due to FEM errors. A
great sensitivity of K to FEM errors was observed, however accurate values of K were obtained, with errors lower than 2 percent.
So, the use of the external forces method for the calculation of K is recommended, considering its simplicity and accuracy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
The abrasion wear resistance and wear mechanism of super bainitic steel austempered at different temperatures and time have been investigated by two-body abrasion testings, scanning electron microscopy, X-ray diffraction, transformation electron microscopy and electron backscattering diffraction. The results show that the two-body abrasion wear mechanism is predominantly micro-ploughing abrasion, and the wear resistance is decreased with increasing isothermal temperature which is attributed to the decreased hardness caused by a higher retained austenite content and the coarsening of the microstructure. The sample austempered at 230°C for 2?h with the higher amount of retained austenite and lower carbon concentration exhibits excellent wear resistance, and the transformation induced plasticity effect is observed during wear process which is beneficial for the improving of hardness and wear resistance. 相似文献
17.
为研究合金元素含量对钢中贝氏体铁素体长大动力学的影响,采用Zener-Hillert和Bosze-Trivedi动力学模型,通过选取热力学和动力学参数,计算了合金成分不同的钢的片层状贝氏体铁素体长大速度.研究表明:Fe-0.59C、Fe-0.81C和Fe-0.478C-4.87Ni合金在贝氏体相变时,贝氏体铁素体长大速度可以用无分配局部平衡条件下的扩散模型很好地描述,Fe-0.69C-1.8Ni-0.8Mo合金贝氏体铁素体长大速度略慢于理论值,Fe-C-8.7Ni合金贝氏体铁素体的长大速度比理论值约慢2个数量级;合金元素含量高的钢的贝氏体铁素体长大速度无法用扩散控制模型很好地描述;结合对贝氏体相变机制的讨论,提出贝氏体相变机制可能与相变温度和钢的成分相关. 相似文献
18.
在热力学,动力学的基础上,从贝氏体铁素体在奥氏体贫碳区切变机制出发,研究了Si对团球状共晶体奥-贝钢中贝氏体相变的影响,并提出Si促使奥氏体奥碳区的形成,有利于贝氏体切变的新观点。 相似文献
19.
Nicolás E. Tenaglia Juan M. Massone Roberto E. Boeri John G. Speer 《Materials Science & Technology》2020,36(6):690-698
ABSTRACTA high silicon cast steel was studied in the as-cast condition in order to characterise its solidification macrostructure and microsegregation. The steel, poured into 32?mm-keel-block-shaped moulds, has a coarse solidification structure and marked microsegregation, containing low-alloyed areas with a total alloy content (Cr?+?Mn?+?Si) of 2.3 wt-% and high-alloyed zones of 5.3 wt-%. The bainitic transformation behaviour at 300°C was studied at different austempering times. The bainitic reaction occurs at different rates within the specimen volume, because of its chemical heterogeneity. An austempering heat treatment leads to an inhomogeneous carbide-free bainitic microstructure with different phase amounts, morphologies and sizes. The heterogeneous distribution of sizes and chemical compositions of retained austenite is speculated to benefit mechanical properties. 相似文献
20.
F.C. Zhang C.L. Zheng B. Lv T.S. Wang M. Li M. Zhang 《Engineering Failure Analysis》2009,16(5):1461-1467
The microstructures on the damaged surfaces of two served bainitic steel crossings were investigated using optical microscope and scanning electron microscope (SEM). The tensile properties of the bainitic steel with different contents of hydrogen were measured. The results showed that the plasticity of the bainitic steel, such as the reduction of area and elongation, decreases sharply with the increase of hydrogen content. There was a critical content of hydrogen without the hydrogen embrittlement for the commercial bainitic steel used for crossing, which was 7 × 10?5 wt%. When the content of hydrogen in a bainitic steel was lower than the critical value, during the used process of the crossings, the wear failure appeared during the early stage; however, the fatigue spalling appeared in the end of the process. When the content of hydrogen was higher than the critical, brittle fracture was responsible for the failure of the crossing in a short time during use. 相似文献