热变形奥氏体动态再结晶的组织表征

研究了Fe-32%Ni合金奥氏体在1000℃、形变速率2×10-3 s-1试验条件下高温变形时的微观组织特征及其演变过程。采用光学显微镜(OM)、电子背散射衍射(EBSD)和透射电镜(TEM)对组织结构进行分析。结果表明:热变形奥氏体发生了不连续动态再结晶,根据形变奥氏体晶粒的位错分布特征,热变形动态再结晶晶粒分为3类:一是位错密度很低的细小晶粒;二是具有位错密度梯度的晶粒;三是高密度位错大体均匀分布的晶粒。     

Enhanced Grain Refining Efficiency Assisted by Martensitic Transformation in Metastable β-Titanium Alloy

利用重复冲击变形技术对比研究了α钛合金Ti-2Al-2.5Zr和亚稳β钛合金Ti-10V-2Fe-3Al变形过程中的微观组织演化及纳米晶的形成机制。金相形貌、X射线衍射及透射电镜观察显示,对于Ti-2Al-2.5Zr合金,塑性变形先后经历了形变孪生、位错活动、剪切等3个过程。与之相反,对于Ti-10V-2Fe-3Al合金,马氏体相变主导着合金的变形。相变分割、剪切及逆向马氏体相变持续贡献于合金的晶粒细化。同时发现,尽管变形到应变量1.2时两类合金组织内均出现纳米晶,但是大量的透射形貌观察显示Ti-10V-2Fe-3Al合金中生成的纳米晶晶粒尺寸更小,纳米晶区域更大。这表明,变形过程中激活马氏体相变可加速材料的晶粒细化。     

马氏体相变加速亚稳β钛合金变形晶粒细化（英文）

利用重复冲击变形技术对比研究了α钛合金Ti-2Al-2.5Zr和亚稳β钛合金Ti-10V-2Fe-3Al变形过程中的微观组织演化及纳米晶的形成机制。金相形貌、X射线衍射及透射电镜观察显示,对于Ti-2Al-2.5Zr合金,塑性变形先后经历了形变孪生、位错活动、剪切等3个过程。与之相反,对于Ti-10V-2Fe-3Al合金,马氏体相变主导着合金的变形。相变分割、剪切及逆向马氏体相变持续贡献于合金的晶粒细化。同时发现,尽管变形到应变量1.2时两类合金组织内均出现纳米晶,但是大量的透射形貌观察显示Ti-10V-2Fe-3Al合金中生成的纳米晶晶粒尺寸更小,纳米晶区域更大。这表明,变形过程中激活马氏体相变可加速材料的晶粒细化。     

非均匀组织FeMnCoCr高熵合金的微观结构和力学性能

提出了一种简单的高熵合金加工工艺,即对Fe-Mn系高熵合金采用中等形变量冷轧和中温短时退火相结合的方法,获得了由晶粒尺寸为数十微米的形变晶粒和超细尺度再结晶晶粒组成的非均匀结构.通过向合金中同时引入由高密度位错、晶粒细化、析出相、ε-马氏体、α-马氏体和回复孪晶等微观结构特征及变形过程中持续发生的形变孪生、ε-马氏体相...     

板条状马氏体的亚结构及形成机制

研究马氏体亚结构及形成机制具有重要理论意义和应用价值.应用35CrMo等材料,淬火为马氏体组织,采用JEM-2100电镜观察马氏体形貌和亚结构,发现35CrMo钢马氏体为板条状,亚结构除了高密度缠结位错外,还有高密度层错.结合2Cr13、Fe-15 Ni-0.6C合金试样的浮凸试验,应用隧道扫描显微镜观察表面马氏体浮雕形貌,测定浮凸的微细尺寸.综合上述试验结果,分析位错、层错形成机制.发现浮凸效应中没有出现位错滑移迹象,认为切变模型不能解释高密度位错和层错的形成.最后应用马氏体相变新机制分析了高密度缠结位错、精细层错的形成.     

γ/ε双相Fe-19Mn合金在拉伸变形过程中的组织演变和加工硬化行为

采用OM、EBSD、TEM、XRD和拉伸实验等方法,研究了γ-奥氏体/ε-马氏体双相Fe-19Mn-0.0017C(质量分数,%)合金在拉伸变形过程中的组织演变和加工硬化行为。结果表明,Fe-19Mn发生了变形诱导马氏体相变,并且随着变形量的增加,相变过程由以γ→ε相变为主转变为以ε→α'相变为主。对比分析加工硬化率的变化与相含量的变化,表明ε→α'相变比γ→ε相变具有更高的加工硬化能力。同时,在变形过程中,ε-马氏体不仅发生了位错滑移,还形成了■孪晶,以满足ε-马氏体的变形协调。在γ→ε和ε→α'双重相变引起的相变诱导塑性(TRIP)效应、γ-奥氏体/ε-马氏体/α'-马氏体中的位错滑移,以及ε-马氏体的孪生变形等机制的共同作用下,Fe-19Mn的抗拉强度和总延伸率分别达到722 MPa和31%,显示出良好的强塑性匹配。     

THE EFFECT OF PRIOR AUSTENITIC GRAIN BOUNDARIES ON NUCLEATION OF(225)_γ MARTENSITE IN STEELS

本文结果指出,T10A及GCr15两钢的单位体积内(225)_γ马氏体片数N_v与原始奥氏体晶粒平均直径D的关系为N_V=N_0(?)~(-1/2).用相变驱动力作用下的低温多晶范性形变的位错理论可推得此关系.据此认为(225)_γ马氏体形核是在相变驱动力作用下,开动位错源的结果.可见,没有预存的马氏体核胚,而只有预存的位错源.细化原始奥氏体晶粒是细化(225)_γ马氏体片的有效方法.     

钢中原始奥氏体晶界对(225)_γ马氏体形核的影响

本文结果指出,T10A及GCr15两钢的单位体积内(225)_γ马氏体片数N_v与原始奥氏体晶粒平均直径D的关系为N_V=N_0(?)~(-1/2).用相变驱动力作用下的低温多晶范性形变的位错理论可推得此关系.据此认为(225)_γ马氏体形核是在相变驱动力作用下,开动位错源的结果.可见,没有预存的马氏体核胚,而只有预存的位错源.细化原始奥氏体晶粒是细化(225)_γ马氏体片的有效方法.     

纳米/超细晶18Cr-8Ni奥氏体不锈钢力学性能及变形机制

采用应变诱发马氏体退火逆相变的方法制备了18Cr-8Ni奥氏体不锈钢的纳米/超细晶组织,并对其力学性能和变形机制进行了分析。通过对奥氏体不锈钢进行室温轧制(压下率为70%)以及分别进行710℃×10 min,760℃×5 min和950℃×5 min的退火处理来获得不同晶粒尺寸的组织。结果表明:纳米/超细晶的平均晶粒尺寸为400 nm,屈服强度为878 MPa,伸长率为33%。对粗晶和纳米/超细晶钢的变形行为进行研究发现,纳米/超细晶钢断口处的显微组织存在大量的应变诱发马氏体和少量的孪晶。然而,在粗晶钢的断口处观察到了应变诱发马氏体、高密度位错和剪切带组织。     

等径角挤压对Fe-18.39Mn合金组织和阻尼性能的影响

采用等径角挤压(ECAP)工艺改变Fe-18.39Mn合金的ε马氏体片形态,进而研究其对合金阻尼性能的影响.在微机控制电液伺服万能实验机上利用自制模具进行ECAP实验,采用倒扭摆测试合金阻尼性能,扫描电子显微镜观察微观组织.结果表明:Fe-18.39Mn合金在300℃进行ECAP后,由于高密度位错的钉扎,阻尼性能丧失;经过600℃退火,没有改变其ECAP后的组织,阻尼性能仍然很低;而在高于700℃的温度退火处理能大量消除高密度位错,并在一定程度上改变ε马氏体片的形态,使ε马氏体片细化,交叉程度降低,进而阻尼性能较未ECAP时得到提高.     

显微结构和杂质对金属注射成形Fe-50%Ni合金磁性能的影响

以羰基铁粉和羰基镍粉为原料,采用金属注射成形(MIM)工艺制备Fe-50%Ni软磁合金.通过对不同工艺条件下试样的杂质含量、密度、金相组织和磁性能的分析,研究显微结构和杂质对磁性能的影响.结果表明:孔隙是影响MIM Fe-50%Ni饱和磁感应强度的主要因素,孔隙、杂质和晶粒尺寸是影响磁导率和矫顽力的因素;最大磁导率、初始磁导率和矫顽力之间存在一定的联系,矫顽力可以作为最大磁导率和初始磁导率的参考依据.通过对比分析孔隙度、杂质含量和晶粒尺寸对矫顽力的影响规律,发现晶粒尺寸是影响MIM Fe-50%Ni合金矫顽力的主要因素.     

Comparison of thermally induced and deformation induced martensite in Fe–29% Ni–2% Mn alloy

The morphology and crystallography of martensite either formed by cooling to subzero temperatures (thermal effect) or by compression deformation were compared for different austenite grain sizes of Fe–29% Ni–2% Mn alloy by transmission electron microscope (TEM). TEM observations revealed both and ′ martensite formation within large grained austenite phases by thermal effect whereas only ′ martensite formation was observed in small grained austenite phases. On the other hand, compression deformation effect caused only ′ martensite formation in both small and large grained austenite phases of Fe–29% Ni–2% Mn alloy. Thermally induced ′ martensite exhibited a lenticular morphology with partial twinnings that are peculiar to this kind of morphology. The crystallographic orientation relationship between austenite and thermally induced ′ lenticular martensites was found to be as Kurdjumov–Sachs (K–S) type relationship.     

退火温度对淬火态Fe-Mn-Si-Cr-Ni合金记忆效应的影响

研究了退火温度对淬火态预先存在热诱发ε马氏体的Fe-14Mn-5.5Si-8.0Cr-5.0Ni合金和无热诱发ε马氏体的Fe-19Mn-5.0Si-8.0Cr-6.0Ni合金记忆效应的影响。结果表明:预先存在热马氏体合金的形状回复率随退火温度的升高,先上升后下降,在500℃附近达到最大值。但无热马氏体存在合金的形状回复率随退火温度的变化却相反,在500℃附近达到最小值;两种合金的Ms温度都随退火温度的升高而下降,在500℃附近达到最低。预先存在热马氏体的合金由于退火后Ms温度的降低,减少了热诱发的马氏体量,因而形状记忆效应得到了提高;而无热马氏体存在的合金由于退火后Ms温度的进一步下降,使得应力诱发马氏体转变更不容易发生,因此形状记忆效应反而下降。     

The effect of heat treatment on the structure and magnetic properties of mechanically alloyed Fe-45%Ni nanostructured powders

Magnetic iron-nickel alloys generally called permalloys are of great interest due to their magnetic properties. Fe-45%Ni alloy is one of the major iron-nickel compositions, well-known for high flux density, low coercivity and their responsiveness to the magnetic annealing. In this study, nanocrystalline Fe-45%Ni alloy powders were prepared by mechanical alloying process using a planetary high-energy ball mill under an argon atmosphere. The synthesized powders were heat treated at different temperatures using a vacuum furnace. The structural properties of the as-milled and the post-heat treated powders were studied by means of X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). The magnetic measurements on the powders were carried out using a vibrating sample magnetometer (VSM). The results showed that the lattice strain decreases and the crystallite size increases with annealing temperature. It was also found that the variation of coercivity is dominated by the removal of residual stress at low annealing temperatures, whereas the value of coercivity depends on the crystallite size at higher annealing temperatures.     

Structural mechanism of reverse α → γ transformation and strengthening of Fe-Ni alloys

Fe-32% Ni alloy subjected to slow heating to a temperature below A _s at a rate of 0.01 K/min demonstrates the untwinning and appearance of an intermediate ? phase with an hcp lattice and lattice parameters a = 2.535, c = 4.132 Å, and c/a = 1.63. Slow heating to 430–490°C leads to the formation of nanocrystalline austenite enriched in nickel, which substantially increases the hardness of martensite. The formation of austenite in the Fe-32% Ni alloy, which is a mixture of martensite with 20–30% nanocrystalline austenite, during its rapid heating to 600°C occurs via the bulk mechanism with short-range atomic diffusion. In this case, the diffusion does not eliminate the concentration micro-inhomogeneity of the alloy in nickel but leads to the reorientation of γ-phase nanocrystals, almost eliminates the dislocation structure, and removes the strengthening by phase hardening.     

Fe-Mn-Si合金在Néel温度以下的γ→ε相变

用电阻法、磁化率和X 光衍射等方法研究了Fe 30Mn 6Si形状记忆合金在Néｅｌ温度以下的γ→ε相变 ,与以前工作不同 ,本文实验结果显示 ,在某些Fe Mn和Fe Mn Si合金中磁转变并不阻止ε马氏体相在Néｅｌ温度以下的生成。     

含氮Fe-Mn合金的阻尼性能和抗腐蚀性能

通过内耗检测技术研究了氮对Fe-14．1Mn和Fe-16．5Mn合金阻尼性能及对Fe-Mn系合金相组成和抗腐蚀性能的影响。结果表明：Fe-14．1Mn比Fe-16．5Mn合金具有更高的阻尼性能;合金中加入质量分数为0．2%的氮,两种合金的阻尼性能略有改变,合金在固溶处理时,发生了γ-ε转变,转变生成的马氏体越多,合金的阻尼性能越好;并且含氮合金在1mol/L硫酸水溶液中的抗腐蚀性能提高2倍。     

Microstructures of ultra-fine grained FeCoV alloys processed by ECAP plus cold rolling and their evolutions during tempering

A new processing method,equal channel angular pressing(ECAP)plus cold rolling(CR),was applied to producing ultra-fine grained FeCoV alloy.The microstructures of ultra-fine grained FeCoV alloy after ECAP,ECAP plus CR,and the effect of tempering treatment on the microstructure of FeCoV alloy produced by ECAP plus CR were investigated.The results show that an elongated substructure with a width of about 0.3μm is obtained after four-pass ECAP using Route A.Cold rolling after ECAP cannot change the morphologies of elongated substructure,and it results in higher fraction of high-angle boundaries and higher dislocation density compared with the identical ECAP without rolling.Subsequent tempering for 30 min at 853 K brings about many nano-phases precipitating at subgrain boundaries and insides the grains,and the size of precipitated phase is measured to be about 10 nm.Nano-phases grow up with increasing tempering temperature and equiaxed structure forms at 883 K.     

钛对铁锰基减振合金阻尼性能和耐蚀性能的影响

采用内耗检测技术研究了Ti对Fe-14Mn、Fe-17Mn和Fe-23Mn合金阻尼性能的影响,研究了Ti对Fe-Mn系合金相组成和耐蚀性能的影响.结果表明,Fe-17Mn比Fe-14Mn和Fe-23Mn具有更高的阻尼性能;在Fe-Mn合金中加入质量分数为1.0％的钛,合金的阻尼性能均受到影响,合金在固溶处理时,发生了γ...     

Atomic force microscope study of the interface of twinned martensite in copper–aluminium–nickel

Atomic force microscopic observations of interfacial structures of twinned γ₁^′ martensite plates in single crystals of Cu–14wt.%Al–3.4wt.%Ni alloy revealed the presence of either side-plate extensions or well-defined twin facets at the martensite/parent phase interface. These results indicate that there are alternative means of accommodating micro-scale mismatch strains at the interface.