应变玻璃转变的相场模拟

应变玻璃转变是在形状记忆合金中发现的一种玻璃化转变过程,这种玻璃化转变过程有着不同于正常马氏体转变的一些特性。通过引入缺陷进而改变形状记忆合金的平均马氏体相的热稳定性和缺陷产生的局部畸变场这两种缺陷的效应,作者课题组建立了新的朗道势能—缺陷模型。通过相场动力学的模拟,成功地预测了实验发现的应变玻璃转变现象及相关的奇异性质。另外,通过相场模拟结果建立了与实验一致的、完整的模拟相变相图,成功地描述了形状记忆合金中除了正常奥氏体态和马氏体态之外的奇异应变态,理论模拟为理解这些应变态及其之间的相关性提供了基础。通过耦合应变玻璃模型和外加力场,模拟了应变玻璃转变的奇异力学特性;其中包括窄的应力应变迟滞回线,应变玻璃成分的应力-温度相变相图,以及在不同的加载情况下,体系在升降温过程中的热滞后性能。本研究工作为进一步通过模拟来指导和设计新型可应用的应变玻璃态材料打下了基础。

普通低碳钢通过应变感生动态转变形成超细铁素体

最近几年，通过在较宽温度范围施加大变形量来生产超细晶粒铁素体钢，已成为全世界关注的重点。奥氏体应变感生动态转变(SIDT)是生产超细铁素体晶粒钢的一个比较好的方法。

高碳高合金钢激光熔凝处理的性能研究

采用CO2 连续波工业激光器在高碳高合金钢Cr12表面进行了激光熔凝处理试验 ,比较了激光处理前后Cr12钢的抗弯强度和耐磨性 ,采用电子显微镜观察了断口特征、断口处和磨面处熔凝层的TEM形貌 ,并用X射线仪测量了抗弯试验前后激光处理层中奥氏体含量随熔凝层深的变化。结果表明 ,激光熔凝处理后获得超细化的枝晶组织 ,其抗弯强度和耐磨性显著提高。在抗弯试验和磨损过程中 ,熔凝层内的奥氏体含量大幅度降低 ,并出现了大量的层错和位错团。晶粒细化 ,奥氏体应变诱发马氏体转变 ,大量位错团的产生是抗弯强度和耐磨性提高的主要原因。

马氏体相变诱发塑性量化表征及合金元素的影响

利用亚稳奥氏作不锈钢低温拉伸曲线的特点，提出了表征相变诱发塑性增量的量化指标：单位体积分数的马氏体诱发的平均塑性增量 Ｄ及本征塑性增量 ＤＩ；且 Ｄ近似等于 ＤＩ．对三种材料的相变诱发塑性的研究表明：钢中碳含量的增加使Ｄ值降低，降低层错能的合金元素有利于Ｄ的增加，而应变速率对Ｄ不产生明显的影响．

Effect of processing route on grain refinement in pure copper processed by equal channel angular extrusion

An experimental study of the microstructures in pure copper billets processed by 8 passes of equal channel angular extrusion （ECAE） via an extended range of processing routes with a 90° die is carried out. Each processing route is defined according to the inter-pass billet rotation angle （χ）, which varies from 0° to 180°. According to the generation of high-angle boundaries and reduction of grain size by electron backscatter diffraction （EBSD） measurements, the grain refinement is found to be most efficient for route with χ=90°and least efficient with χ=180°, among the seven routes studied. This trend is supported by supplementary transmission electron microscopy （TEM） measurements. Comparison of the EBSD and TEM data reveals the importance of considering the non-equiaxity of grain structures in quantitative assessment of microstructural differences in ECAE-processed materials.

Effect of external stress and bias magnetic field on transformation strain of heusler alloy Ni-Mn-Ga

The influence of external field(magnetic field and stress field) on the transformation strain of Ni 52.9- Mn 24.4Ga 22.7 single crystal were investigated and its mechanism was also discussed. When thermally martensitic transformation occurs, about 0.25% transformation strain is obtained which may be obviously enhanced to about 0.8% by a 6 000 Oe magnetic bias field. However, the strain decreases by the external compress stress loaded along the strain-measured direction. When the external compress stress and bias magnetic field are simultaneously applied, the transformation strain decreases with increasing the magnetic field, which is related to the rearrangement of the martensite variants influenced by the external field.

影响钛合金屈强比的因素及作用机理探讨

以典型琢型和琢＋茁型钛合金作为研究对象,对该合金从合金成分、晶体结构、组织类型和加工方式等方面进行分析,总结了钛合金屈强比的影响因素并对其作用机理进行了探讨。结果表明,钛合金的密排六方（hcp）晶体结构滑移系少,抵抗塑性变形能力大,决定了其屈强比较高。在实际工程实践中,钛及钛合金的屈强比波动范围大,在0.62~0.99,可调节性强。工业纯钛中O元素作为间隙杂质元素使材料强化和脆化,随着氧含量的增加,屈强比升高。钛合金屈强比具有“取向性”,沿轧制方向屈强比较低,沿单一加工方向（长度方向）加工变形量越大,材料的屈强比越低。TC4钛合金在淬火后形成亚稳定的转变组织,由于应变引起的转变,使材料均匀伸长率提高,这增大了抗拉强度与屈服强度的比值,屈强比降低。

Three dimensional finite element study on torsion extrusion processing of 1050 aluminum alloy

The capability of the torsion extrusion （TE） process as a severe plastic deformation （SPD） method was compared with the conventional forward extrusion （FE） process. The TE and FE processes were successfully performed on AA1050 alloy samples at room temperature. To simulate the above mentioned processes, finite element analysis was carried out using the commercial elasto-plastic finite element analysis ABAQUS/Explicit Simulation. It is shown that load requirement for the TE process is lower than that for the FE process. The equivalent plastic strain calculated by the FEA proved that higher values of strain are imposed to the sample in the TE process. The strain distribution for the TE sample at the final stage of extrusion shows smoother strain gradient in comparison with the one produced by the FE process.

通过高温变形提高铌微合金钢热延展性

连铸生产低碳铝镇静钢时，在矫直阶段的热延展性损失主要来自于不同的微合金化元素，特别是其中的铌元索。同时，这些元素也是影响产品机械性能的主要元素。因为不能通过改变化学成分解决这个问题，所以，为了提高钢的延展性，我们研究热机械加工工艺，以此途径解决这个问题。试验采用铌微合金钢作为研究对象，同时考虑连铸工艺过程中所发生的热交换。首先，应该注意按照热制度进行原位熔化的钢具有较低的热延展性。其次，研究了实施热制度后，在接近δ→γ转变时，采用变形处理对热延展性的影响，这种变形可显著提高钢的热延展性。最后，讨论了采用这种方法提高热延展性的机理。

Inversion of the Volumetric Strain of Aquifer According to the Tidal Effect of Groundwater in North China

The change of the confined aquifer level reflects the pore pressure change,and the pore pressure change of the aquifer is closely related to the aquifer pressure. This paper uses the tidal response of the well water level data in the North China region to calculate the tidal factor of each well and extract the effective water trend information. Then,the volumetric strain of an existing confined aquifer well in the North China region is inverted,and the contour maps are plotted on a half-year scale from 2009 to 2012. Results show that it can reflect the state of stress and strain in deep crust to a certain extent in the North China region.

Kinetic calculation for the reaction of H with Si_2H_6 using the variational transition state theory

The reaction of disilane with atomic hydrogen has been studied. This reaction involves both substitution and abstraction. Calculations show that the hydrogen abstraction is the strongest competing channel. The canonical variational transition state theory with a small curvature tunneling correction (SCT) has been used for the kinetic calculation. The theoretical results are in good agreement with the available experimental data. Comparing the reactions of atomic hydrogen with disilane and silane, it can be seen that the reactivity of the Si-H bond is higher in Si2H6than that in SiH4.