奥氏体钢层错能与ε马氏体相变

导出了在奥氏体钢中相变驱动力与层错能的关系以及层错能和应变能对马氏体形态的影响规律。估算了低碳、氮含量的低温奥氏体钢中层错扩展时的晶格摩擦阻力(约为相变驱动力的18％)。临界层错能约为150mJ／mz。     

低温奥氏体钢相变的结构参数

研究了低温奥氏体钢中层错能和强度对相变的作用，导出了相变临界分切应力和层错能与强度之间的关系式，发现奥氏体相变结构参数对马氏体相变特性有很大影响。     

低温奥氏体钢的强度计算

研究了低温奥氏体钢的强度随温度及合金元素含量的变化规律。对大量试验结果用计算机处理得到了定量计算的系列表达式。经验证,计算结果是令人满意的,可用于低温奥氏体钢的设计和强度计算。     

高氮奥氏体钢的韧脆转变与层错能的关系

在-60℃至室温范围内,采用夏比冲击试验测定材料的韧-脆转变温度,并通过对冲击断口的X-射线测试层错能等方法,对几种不同含氮量奥氏体不锈钢在低温下发生韧-脆转变的现象进行了研究。结果表明：在超高氮奥氏体钢中,随氮质量分数的增加该钢种发生韧-脆转变的温度上升,层错能减少,韧性越来越差。     

高锰TWIP钢层错能的研究进展

高锰TWIP钢的高强度、高塑性和高能量吸收能力与其堆垛层错能有关。TWIP效应对应的层错能上、下限值仍未统一,尤其是TWIP向MBIP(微带诱导塑性)转变的临界判据仍有待于深入分析。XRD、TEM和EAM是测定奥氏体层错能最常用的实验方法。同一TWIP钢的层错能及其变化规律存在实验方法的相关性。正规和亚正规溶液模型、Bragg-Williams模型和双亚点阵模型是计算高锰钢层错能的常见模型。对同一TWIP钢来说,不同模型的预测值并不相同,且与实测值也存在差异。铃木效应引起层错能随间隙原子浓度非线性变化,这在计算时是不能忽略的。规范实验方法、提高设备精度和完善热力学模型及其数据库有助于获得准确可靠的层错能值。     

钢中层错能的测定、计算和应用

介绍了铁基合金中层错能的计算模型、各项热力学参数的来源及计算实例;阐述了以X射线衍射分析测定钢中层错几率的原理和方法,给出了Fe-Mn-Si-C系层错几率与成分的关系式、层错能和层错几率的关系式以及层错几率与马氏体相变驱动力关系式,可为设计孪晶诱发塑性钢提供理论基础。     

奥氏体钢马氏体相变点M_s、M_（εs）

在计算机上回归处理了大量试验结果，得到了奥氏体钢的Ｍ＿ｓ、Ｍ＿εｓ定量经验计算式：Ｍ＿ｓ（Ｋ）＝７３１－２２７（Ｃ＋Ｎ）－１７．６Ｎｉ－２２．５Ｍｎ－１７．３Ｃｒ－１６．２ＭｏＭ＿εｓ（Ｋ）＝６３０－２６１．４（Ｃ＋Ｎ）－１３．７Ｍｎ－１３．１Ｃｒ－１７．９Ｎｉ－３８．５Ａｌ在热力学上从层错能及Ｍ＿ｓ、Ｍ＿εｓ的相对变化角度较好地解释了奥氏体钢的γ→α，γ→ε→α，γ→ε相变，并且进一步用试验数据验证，结果也较满意。     

铝、铜、铬合金元素对Fe-21Mn-0.4C TWIP/TRIP钢层错能和力学性能的影响

参考文献建立了Fe-Mn-C合金层错能的热力学模型,用模型计算了铝、铜、铬元素对Fe-21Mn-0.4C合金层错能的影响规律;在Fe-21Mn-0.4C合金中添加合金元素,研究其对层错能的影响。研究结果表明:铝和铜增加合金的层错能,而铬则降低合金的层错能;当层错能低于10.7 mJ/m2时,Fe-21Mn-0.4C合金相组成为γ+ε,当层错能为10~19.02 mJ/m2时,合金的相组成为γ+ε+a,当层错能高于19.02 mJ/m2时,合金的相组成为单相的γ;层错能的变化和添加了合金元素铝、铜、铬的Fe-21Mn-0.4C合金性能变化没有相一致的关系,说明影响Fe-21Mn-0.4C合金力学性能的因素很多,需要进一步的研究。     

氮对Fe-38Mn奥氏体钢低温冲击韧性的影响

研究了不同氮含量对真空熔炼的Fe-38Mn合金77K冲击韧性及断口形貌的影响。结果表明适当氮含量可以显著提高Fe-38Mn合金的低温冲击性能，其断口形貌由沿晶断裂断口转变为准解理断口。     

电渣重熔对奥氏体钢低温韧性的影响

测定了77K下22Mn-13Cr-5Ni-0.25N奥氏体钢电渣重熔前后的冲击韧性、氢含量及夹杂物含量,并利用扫描电子显微镜和透射电子显微镜研究了电渣重熔对该钢低温韧性的影响,结果表明：电渣重熔使钢中氢和夹杂物含量显下降,有利于抑制γ→ε转变,减小应力集中,从而提高了该,多的低温韧性。     

Weak Beam TEM Study on Stacking Fault Energy of High Nitrogen Steels

The nature of the high work‐hardening rate of nitrogen bearing steels was examined focusing on the stacking fault energy (SFE). The dislocation configuration and the width of dissociated dislocations were evaluated in various kinds of austenitic stainless steels with and without nitrogen, using the weak beam method. Nitrogen addition resulted in changing the dislocation configuration from tangled to planar. Nitrogen was, however, found to increase the SFE rather than decrease as reported previously and the SFE can be formulated as a function of chemical composition, SFE(mJ/m²) = 5.53 ‐ 0.16 (wt%Cr) + 1.40 (wt%Ni) + 17.10 (wt%%N). These results indicate that dislocation planarization by nitrogen addition is inadequately explained in terms of SFE.     

层错能对高能球磨铜合金的影响

试验中以球磨的方法制备了一系列不同成份的Cu—Zn及Cu—Al合金（层错能〈75MJ／m^2）。对Zn和Al的固溶强化效果及其降低铜合金层错能的作用进行了研究。实验结果显示,随着Zn或Al含量的升高,（试样的）显微硬度（HV）值增加,符合固溶强化的规律。在相近原子百分比的条件下比较Cu—Zn和Cu—Al合金的HV值,显示当合金中无第二相出现时,Zn的固溶强化效果优于Al;另一方面,随着Zn％及Al％（原子百分比）的增加,Cu～Zn及Cu—Al合金的层错能下降,而层错能的降低导致了强化的产生,这种情况下Zn和Al的不同强,L化效果可以用公式k=Gb/2π（1-v）（a-δ·FE）^[1]来评价,式中K是Hall—Petch关系的斜率。评价的结果与实验数据（合金的显微硬度值）是相吻合的。     

Effect of Carbon Content on Stacking Fault Energy of Fe-20Mn-3Cu TWIP Steel

The influence of carbon content on the stacking fault energy(SFE)of Fe-20Mn-3Cu twinning-induced plasticity(TWIP)steel was investigated by means of X-ray diffraction peak-shift method and thermodynamic modeling.The experimental result indicated that the stacking fault probability decreases with increasing carbon addition, the SFE increases linearly when the carbon content in mass percent is between 0.23% and 1.41%.The thermodynamic calculation results showed that the SFE varied from 22.40to 29.64mJ·m-2 when the carbon content in mass percent changes from 0.23%to 1.41%.The XRD analysis revealed that all steels were fully austenitic before and after deformation,which suggested that TWIP effect is the predominant mechanism during the tensile deformation process of Fe-20Mn-3Cu-XC steels.     

The Effect of Disorder on the Concentration‐Dependence of Stacking Fault Energies in Fe1‐xMnx – a First Principles Study

The stacking fault energy plays a significant role in defining the type of plasticity mechanism which prevails in high‐Mn steels. Therefore, a detailed understanding and control over the physical mechanisms that influence the stacking fault energies is crucial for effective design and optimization of such steels. We present results of a first principle study on the influence of the chemical and magnetic ordering on the composition dependence of stacking fault energies in austenitic Fe_1‐xMnx alloys, which are prototypes for high‐Mn steels. Our calculations show that chemical ordering has a significant influence on the intrinsic stacking faults. We have further demonstrated that, although FeMn‐alloys have zero net magnetization, the internal magnetic structure significantly changes the properties of the stacking faults. Specifically, we have shown for chemically disordered structures that the dependence of the equilibrium volume and of the SFE on their composition is strongly changed if they are under paramagnetic instead of non‐magnetic exposure. These results prove the importance of atomistic simulations for the determination of the SFE and clearly indicate that the magnetic interactions and the chemical ordering in this system must be accurately captured by the theory.     

热轧590MPa级车轮钢的奥氏体相变行为

 利用热力模拟试验技术,研究一种Nb-V-Ti复合微合金化C-Mn钢的奥氏体连续冷却相变行为,为低成本高性能热轧590MPa级车轮钢的控制轧制和控制冷却工艺制定提供必要的理论依据。研究表明：无形变条件下,铁素体转变存在的冷却速率范围为0. 5~5℃/s,珠光体转变存在的冷却速率范围为0. 5~2℃/s;形变条件下,铁素体转变存在的冷却速率范围为0. 5~25℃/s,珠光体转变存在的冷却速率范围为0. 5~10℃/s;不论是否存在形变,贝氏体转变存在于整个冷却速率范围(0. 5~30℃/s);奥氏体区形变增加了奥氏体内部的缺陷密度,促进了非均匀形核的发生,故形变促进了铁素体转变;由于试验钢的碳的质量分数较低(＜0. 10%),形变通过促进铁素体相变而间接促进珠光体相变;当贝氏体相变前无铁素体相变时,形变对贝氏体相变有促进作用;试验钢在实际热轧试验中冷却速率宜控制在20℃/s左右,卷取温度控制在550~650℃。     

Effect of Carbon Fraction on Stacking Fault Energy of Austenitic Stainless Steels

The effect of C fraction (C/N) on stacking fault energy (SFE) of austenitic Fe-18Cr-10Mn steels with a fixed amount of C?+?N (0.6?wt pct) was investigated by means of neutron diffraction and transmission electron microscopy (TEM). The SFE were evaluated by the Rietveld whole-profile fitting combined with the double-Voigt size-strain analysis for neutron diffraction profiles using neutron diffraction. The measured SFE showed distinguishable difference and were well correlated with the change in deformation microstructure. Three-dimensional linear regression analyses yielded the relation reflecting the contribution of both C?+?N and C/N: SFE (mJ/m²)?=??C5.97?+?39.94(wt pct C?+?N)?+?3.81(C/N). As C fraction increased, the strain-induced ?????? martensitic transformation was suppressed, and deformation twinning became the primary mode of plastic deformation.