Upward modulus trend in NiAl and NiFeAl single crystals

Dynamic Young modulus, torsion modulus and elastic energy dissipation were measured in Ni_56.2Fe_0.3Al_43.1Ta_0.3Mo_0.1 (NiAl crystal) and Ni_56.6Fe_12.3Al_30.2Hf_0.6(Al₂O₃)_0.3 (NiFeAl crystal). The elastic constant C′=(C₁₁−C₁₂)/2 has in both alloys a positive temperature derivative: (dC′/dT)>0 from 150 K up to 1300 K. The elastic energy dissipation exhibits a Debye-like peak whose activation energy is 2.36±0.05 eV in NiAl and 1.98±0.09 eV in NiFeAl. The peak is described as a Zener’s pair reorientation.     

Spin and valence state equilibria of cobalt and magnetic properties of LaCoO3

On the basis of the spin and valence state equilibria and superexchange interaction of the various cobalt ions in LaCoO₃, an approximate semiempirical formula has been proposed and used to calculate magnetic susceptibilities of LaCoO₃ over a wide temperature range (100–1200 K). The results indicate that there are thermodynamic equilibria between the low spin state Co^III (t_2g⁶e_g⁰) ion, the high spin state Co³⁺ (t_2g⁴e_g²) ion, the Co^II (t_2g⁶e_g¹) ion and the Co^IV (t_2g⁵e_g⁰) ion in LaCoO₃. The energy difference between the low spin state Co^III and the high spin state Co³⁺ is about 0.006 eV. The content of the low spin state Co^III ion is predominant in LaCoO₃ and the content of the high spin state Co³⁺ ion varies with temperature, reaching a maximum at about 350 K, then decreasing gradually with increasing temperature. At low temperature the contents of the Co^II ion and the Co^IV ion in LaCoO₃ are negligible, while above 200 K the contents of both the Co^II ion and the Co^IV ion increase with increasing temperature; however, the content of the Co^II ion always is larger than that of the Co^IV ion at any temperature. These calculated results are in good agreement with experimental results of the Mössbauer effect, magnetic susceptibility and electrical conductivity of LaCoO₃.     

Nb对奥氏体热变形后等温回复的影响

采用热模拟实验研究了不同Nb含量的低C高Mn钢在800—900℃变形后奥氏体的回复特征,同时借助Fe-40%Ni-0.1%Nb(质量分数)合金揭示了回复过程中的位错演化及析出行为,建立了位错滑移及溶质拖曳机制的等温回复动力学模型,据此计算拟合了应力松弛曲线上回复实验数据,计算结果与理论分析及实验结果相符.实验及模拟结果表明,Nb溶质拖曳及析出均减慢回复过程,提高变形积累;与Nb溶质拖曳相比,析出能够更有效地延缓回复软化;Nb溶质拖曳通过升高回复激活自由能U0及减小激活长度来实现回复过程的延缓,提高溶质Nb含量,将升高Uo和减小激活长度.对于含Nb低C高Mn微合金钢,在道次间隔短的多道次热连轧精轧阶段,变形积累主要依靠Nb溶质拖曳作用,而对于轧制节奏较慢的中厚板精轧,轧制变形的积累依靠Nb溶质拖曳与析出的共同作用.     

On the vapourization thermodynamics of cobalt trifluoride

The sublimation of CoF₃(s) was studied. The temperature dependence of the total vapour pressures as measured by the torsion method in the temperature range 700–830 K fit on the equation:

log(p/kPa)=(11.60±0.20)−10630±400)/(T/K)

Both the sublimation reactions:

Cof₃(s)= Cof₃(g) (1)

2Cof₃(s)=2Cof₂(s)+F₂(g) (2)

occur during the vapourization of CoF₃(s) where the molar fraction of the reaction (1) was found equal to 0.60±0.05, practically constant in the covered experimental temperature range. The standard enthalpies Δ_subH°(298)=216±4 and 204±3 kJ mol⁻¹ for reactions (1) and (2) respectively were derived from second- and third-law treatment of the data. New values for the enthalpy of formation of CoF₃(s) and CoF₃(g) equal to −773±5 and −557±10 kJ mol⁻¹, respectively, were derived.     

Nb微合金化低碳贝氏体圆钢的组织细化

通过热模拟试验研究了Nb微合金化在长材低碳贝氏体钢中的作用机理。研究表明对该成分的低碳贝氏体钢采用线棒材轧制时,形变诱导析出Nb(CN)抑制再结晶主要发生在轧后过程中,抑制了轧后相变前的奥氏体晶粒长大,同时抑制了贝氏体板条束的长大。变形后在空冷条件下,3 s后开始发生明显的析出,在900℃以下变形,在贝氏体相变前,可获得约10μm的均匀细小的奥氏体晶粒。     

Sublimation enthalpy of tellurium tetrabromide by the torsion effusion method

The total vapour pressure of TeBr₄(s) was measured in the temperature range 423–485 K by the torsion effusion method. The total pressure as a function of temperature can be represented by the following equation: log(p/kPa)=(11.17 ± 0.20) − (6104 ± 100)(K/T)

The equilibrium involved in the vaporation process is described by: (x + y)TeBr₄(s) → xTeBr₄(g) + yTeBr₂(g) + yBr₂(g) where x = 0.06 and Y = 0.47.

The reaction enthalpy ΔH⁰(298) = 119 ± 4 kJ mol⁻¹ was obtained from the second and third law treatment of the data.     

Assessment of austenite static recrystallization and grain size evolution during multipass hot rolling of a niobium-microalloyed steel

Double-deformation isothermal tests and multipass continuous-cooling hot torsion tests were used to study the evolution of austenite microstructures during isothermal and non-isothermal hot deformation of an Nb microalloyed steel. These tests, coupled with microstructural characterization, have verified that the no-recrystallization temperature (T _nr ) corresponds roughly to the temperature where recrystallization starts to be incomplete during rolling. An accurate method to estimate the recrystallized fraction during hot rolling based on stress-strain data, and which does not require metallographic studies, is proposed. The results of this method have been successfully compared to metallographic measurements, the values of non-isothermal fractional softening and the accumulated stress measured in the plots of mean flow stress (MFS) versus the inverse of temperature. A remarkable austenite grain refinement occurs in the first hot rolling passes after reheating. The correlation of isothermal and continuous cooling tests is better understood if the effect of grain size on recrystallization and precipitation is taken into account.     

富铜相对Fe-3%Si-Cu合金再结晶行为的影响

以2块热轧Fe-3%Si-Cu合金板为研究对象,分别过时效处理和固溶处理后多道次冷轧再进行500~800 ℃再结晶退火处理,分析了合金再结晶退火后的显微组织及不同再结晶退火工艺下合金的硬度变化,从而研究了冷轧Fe-3%Si-Cu合金的再结晶行为。结果表明,热轧试样经650 ℃过时效处理后有椭球形或棒状的面心立方ε-Cu相析出,棒状富铜相的尺寸较大,其长轴≥100 nm。不同工艺热处理的试样经冷轧后均表现出随退火温度的升高,完全再结晶时间缩短,且由于富铜相的析出,经固溶处理后的试样退火后其再结晶时间明显比过时效处理后试样的短。当再结晶退火温度为500 ℃时,冷轧前进行了固溶处理的试样出现了回复引起的软化不足以抵消析出造成的硬化的现象,在10⁴ s时硬度曲线上出现明显的时效硬化峰;在600 ℃以上退火时,则表现出再结晶占优势的退火特征,硬度曲线没有明显的时效硬化峰。     

热变形对含铌奥氏体不锈钢07Cr18Ni11Nb再结晶行为的影响

采用热模拟压缩及中试热轧的试验方法,研究了热变形对含铌奥氏体不锈钢07Cr18Ni11Nb再结晶行为的影响。结果表明:热压缩变形时,试验钢再结晶程度随变形温度、变形量的升高以及变形后保温时间的延长逐渐增大;变形温度越高、变形量越大,发生再结晶所需的保温时间越短;保温时间越长,再结晶晶粒长大越明显;轧制变形时,热轧板1/4厚度处更容易发生再结晶,随着轧制温度和变形量的升高,1050 ℃轧制变形25%时可在全厚度获得完全再结晶组织。     

高强度热镀锌结构钢SGC570带钢的研发与应用

采用低成本的合金成分设计体系,通过连铸连轧和酸轧工序,以及低温退火的连续热镀锌生产工艺,成功开发了0.3~2.5 mm厚570 MPa级高强度热镀锌结构带钢。热连轧精轧出口温度为870 ℃,采取前段层流冷却,卷取温度为600 ℃,热镀锌工艺采用均热温度为605 ℃的不完全退火工艺;产品屈服强度Rp0.2为592～619 MPa,抗拉强度R_m为609～638 MPa,伸长率A50为6.5%~15%,组织性能均满足标准及用户要求,实现了批量稳定的工业化试制生产。     

Q345E���Ʊ����ѧ���ܵ�̽��

 在未控轧控冷的轧制条件下,Q345E钢材终轧温度较高,铌推迟形变奥氏体再结晶的作用不明显。虽然铌/钒复合微合金化钢晶粒有一定程度的细化,由于微合金元素的沉淀强化及热轧态组织中贝氏体的出现,导致含铌微合金化钢低温韧性不能满足使用要求。通过对Q345E钢化学成分进行控制,结合控轧控冷技术,并采取合理的热处理工艺,使Q345E钢在保证高强度的基础上,－40 ℃低温冲击韧性得到明显提高。     

Thermoelectric properties of Ni- and Zn-doped Nd2CuO4

The electrical resistivity, Seebeck coefficient, and thermal conductivity of Nd₂(Cu_0.98M_0.02)O₄ (M: Ni and Zn) have been measured in the temperature range from room temperature to about 1000 K. Ni- and Zn-doping decreases the electrical resistivity and the absolute values of the Seebeck coefficient. The thermal conductivity decreases with increasing temperature, showing phonon conduction, and also decreases by doping. The power factor of Nd₂(Cu_0.98Ni_0.02)O₄ reaches 1.02×10⁻⁴ W m⁻¹ K⁻² and the figure of merit is 1.35×10⁻⁵ K⁻¹ at 320 K. The relatively low figure of merit compared with that of the state-of-the-art thermoelectric materials is due to the high thermal conductivity.     

热轧工艺对超纯Cr17铁素体不锈钢成形性能的影响

对一种铌、钛双稳定化的超纯Cr17铁素体不锈钢分别进行常规热轧和低温热轧,再依次进行相同的退火、冷轧及最终再结晶退火处理。对比研究两种热轧工艺对组织、织构演变及成形性能的影响规律。结果表明,与常规热轧相比,低温热轧能显著细化热轧组织、弱化α纤维织构并强化γ纤维织构,最终使冷轧退火板的γ纤维再结晶织构明显增强、偏离{111}<121>组分的程度显著降低,使珋r值增大、△r值减小。低温热轧是改善超纯Cr17铁素体不锈钢成形性能的有效途径。     

ON THE HOT WORKABILITY OF LOW-CARBON Mn-Nb STEEL

用扭转实验方法,对低碳锰铌钢进行了研究.建立了幂函数形式的本构方程.确定了稳态流变应力与热塑性之间的关系.考虑到累积应变效应,对动态再结晶过程进行了初步研究.分析了温度、应变率、Nb(CN)沉淀对动态软化百分数的影响.动态再结晶过程中,激活能和应力指数的变化,在一定程度上反映了Nb(CN)的沉淀.定义(?)/(?)为沉淀指数,用以定量地说明温度,应变率对Nb(CN)沉淀过程的影响.此外,还对应变率敏感系数与温度,剪切应变之间的关系进行了研究.     

Power factor of La1−xSrxFeO3 and LaFe1−yNiyO3

The electrical conductivity (σ), Seebeck coefficient (S), and power factor (σS²) of perovskite-type LaFeO₃, La_1−xSr_xFeO₃ [0.1 ≤ x ≤ 0.4] and LaFe_1−yNi_yO₃ [0.1 ≤ y ≤ 0.6] were investigated in the temperature range of 300–1100 K to explore their possibility as thermoelectric materials. The electrical conductivity of LaFeO₃ showed semiconducting behavior, and its Seebeck coefficient changed from positive to negative around 650 K with increasing temperature. The electrical conductivity of LaFeO₃ increased with the substitutions of Sr and Ni atoms, while its Seebeck coefficient decreased. The Seebeck coefficient of La_1−xSr_xFeO₃ was positive, whereas that of LaFe_1−yNi_yO₃ changed from positive to negative with increasing Ni content. The substitutions of Sr and Ni were effective in increasing the power factor of LaFeO₃; 0.0053 × 10⁻⁴ Wm⁻¹ K⁻² for LaFeO₃ (1050 K), 1.1 × 10⁻⁴ Wm⁻¹ K⁻² for La_1−xSr_xFeO₃ (x = 0.1 at 1100 K) and 0.63 × 10⁻⁴ Wm⁻¹ K⁻² for LaFe_1−yNi_yO₃ (y = 0.1 at 1100 K).     

Stability of rolling texture during heat treatment in a two-phase Ti3Al base intermetallic alloy

The stability of hot rolling texture developed in the ₂ phase of a two-phase Ti₃Al base intermetallic alloy, during subsequent heat treatment, has been systematically investigated. The basal hot rolling texture remains rather stable during recrystallization annealing at temperatures within the single phase ₂ range. Grain growth after recrystallization produces extra orientations other than the basal. For the material with a starting basal texture, heat treatment in the upper ₂, (₂+β) or β phase fields does not change the basic character of the texture, although the sharpness and especially the width of the basal component increase to some extent with the increase in the heat treatment temperature. Heat treatment of material with starting non-basal texture in the upper ₂, (₂+β) or β phase fields does not produce any basal component irrespective of the heat treatment temperature. When the starting material is reasonably strain free and possesses a weak basal texture, heat treatment in the upper ₂, (₂+β) or β phase fields helps in intensifying the basal component to a certain extent.     

铁素体不锈钢中铜析出相的长大和晶体结构演化规律研究

为研究铁素体不锈钢中铜析出相的析出过程和晶体结构演化规律,采用原子探针层析技术(APT)和高分辨透射电子显微镜(HRTEM)观察了铜析出相的长大过程。结果显示:随着时效时间的延长,富铜相尺寸增大,数量密度降低,析出相形状由最初的球状转化为椭球状,最后成为杆状。析出相长大曲线可以拟合为r₁=2.45t^1/3-4.46,符合Ostwald熟化规律。9R结构与基体的取向关系为(114)_9R//(011)_a-Fe,[110]_9R//[111]_a=Fe。本实验钢含铜相析出序列为bcc→9R→3R→fcc。     

热模拟Q890高强钢焊接过程中组织转变的原位观察

采用高温激光共聚焦显微镜对6 mm厚Q890高强钢板进行了焊接热模拟试验。通过原位观察研究了不同焊接热输入条件下钢板显微组织的形核和核长大过程。结果表明:焊接后在t_8/5为300 s的条件下冷却的钢板奥氏体晶界析出块状铁素体,室温组织为先共析铁素体、粒状贝氏体和少量板条贝氏体;在t_8/5为60 s的条件下冷却的钢板,贝氏体转变从奥氏体晶界开始,室温组织主要为针状铁素体、板条贝氏体和粒状贝氏体;在t_8/5为30 s的条件下冷却的钢板,板条贝氏体呈缠结互锁状,室温组织主要为板条贝氏体和板条马氏体;在t_8/5为15 s的条件下冷却的钢板室温组织为板条马氏体及少量板条贝氏体。通过采用高温激光共聚焦显微镜进行焊接热模拟试验并结合组织转变的原位观察来判定高强钢钢焊接性能是可行的。     

薄板坯连铸连轧过程中的动态软化行为研究

利用Gleeble—2000热/力模拟试验机模拟了低碳含Nb钢在薄板坯连铸连轧生产过程中的动态软化行为,分析了Nb含量对动态再结晶的影响,建立了低碳含Nb钢的动态再结晶模型,并绘制了动态再结晶区域分布图。     

Cr22Ni13Mn5Mo2N奥氏体不锈钢的热轧工艺

运用Gleeble-3800热模拟试验机研究了00Cr22Ni13Mn5Mo2N奥氏体不锈钢在变形温度为1000～1200 ℃,变形量为50%、60%、70%,应变速率为0.05 s^-1条件下的热压缩变形行为,并观察分析变形后试样组织形貌和经1080 ℃固溶热处理后试样的组织形貌。观察试样固溶热处理前后的组织形貌得到在1000~1150 ℃下进行热压缩变形,随着变形量的增加,动态再结晶越完全;经过固溶热处理后,静态再结晶就越充分。但在1200 ℃时,温度过高,再结晶已完成并且晶粒发生长大。在变形量分别为50%、60%和70%时,随着变形温度的升高,再结晶越完全,经固溶热处理后,再结晶更完全。00Cr22Ni13Mn5Mo2N奥氏体不锈钢热轧最佳轧制温度为1100 ℃,压缩变形量为70%。