Sm0.99Gd0.01Al2金属间化合物的声学和比热容性质研究

用感应悬浮冷坩锅法制备了单相性良好的Sm0.99Gd0.01Al2多晶金属间化合物．对其低温的声学和比热容性质进行了研究，得到了样品模量和声衰减以及随温度变化的规律．研究表明，在磁相变附近，样品的声学性质有剧烈的反常现象．比热容测量的结果表明这是一个二级相变．结合样品的磁性性质，对其声学特性进行了分析。     

贝氏体相变理论—两个一级相变耦合的模型

建立了一种贝氏体相变的Ｇｉｎｚｂｕｒｇ－Ｌａｎｄａｕ理论模型，该模型设计了贝氏体相变的一种耦合机制，即转变过程包含两个一级相变，一个具有重构特征，另一个为位移相变。由数值计算结果，建议了一种扩散诱导形核机制及扩散伴随伴移生长机制。     

Ti80钛合金相变点的测定

采用计算法和连续升温金相法2种方法研究了Ti80钛合金相变点.根据合金中主元素及杂质元素含量对相变点的影响,推算出了Ti80钛合金的相变温度.通过连续升温金相法,观察不同淬火温度下合金的显微组织变化,将升温过程中初生α相完全消失的温度定为Ti80钛合金的相变点.结果表明,采用两种方法所得数据相近,本批次Ti80钛合金的相变点为1025℃.     

物理分析法与金相法测定BT25钛合金相变点

针对BT25两相钛合金,对比研究了计算法、热膨胀法、差示扫描量热法和连续升温金相法4种方法测定(α+β)/β相变点的一致性问题。计算法根据各合金元素及杂质含量对钛合金相变点的影响值,推算出公式,得出BT25合金的相变点约为1023℃;热膨胀法和差示扫描量热法根据钛合金发生(α+β)→β转变时体积和热量的变化,测得BT25合金的相变点约分别为1029.2和1029.85℃;而连续升温金相法通过观察不同淬火温度的试样在光学显微镜下的显微组织变化,确定升温过程中初生α相完全消失的温度即为相变温度,约为1029℃。结果表明采用计算法、热膨胀法和差示扫描量热法与金相法测定BT25钛合金的(α+β)/β相变点一致,基于多种测定方法的综合运用对于钛合金相变点的准确测定具有重要意义。     

淬火工艺有限元模拟中弹塑性比例系数的计算方法

淬火过程是一个温度、相变、应力应变相互影响的材料非线性过程。根据淬火过程的特点,提出了一种新的计算弹塑性比例系数的方法,使用该方法可以求解过渡单元的弹塑性比。在模拟过程中,为了提高计算精度、减少计算时间,提出了两种加速弹塑性比例系数收敛的方法:弹性逼近法和插值方法。应用弹性逼近法和插值方法对无相变冷却过程和有相变冷却过程进行有限元模拟,将模拟所得应力变化曲线与实验结果相比较。结果表明,弹性逼近法和插值方法可以显著减少弹塑性比例系数的迭代次数,计算得到的应力值与实验结果吻合较好。     

时效处理对TiNiCr形状记忆合金相变的影响

利用差示扫描量热仪(DSC)、扫描电镜(SEM)和D/max2500PC全自动X射线衍射仪研究了不同时效处理制度下TiNiCr合金相变温度的变化规律.结果表明,该合金随着时效温度增加,逆马氏体相变点As、Af上升,但当时效温度高于700℃时,相变点As、Af降低.该合金在冷却过程中经历了B2→R→B19′两阶段一级相变.通过SEM和XRD衍射研究表明,该合金经时效处理产生了Ti3Ni4析出相诱发了R相变.     

相变超塑性实验测温方法研究

在相变超塑性快速热循环的温度测量方法研究中,本文选用红外亮度测温仪,将所输出的温度信号进行线性放大,使相变热效应现象在温度-时间曲线上得到明显的显示。利用相变点为内标,该系统可以较精确地测量快速热循环中试样的温度。     

BT23钛合金β转变温度的测定与分析

文章采用化学成分计算法、组织分析计算法、差热分析法和连续升温金相法4种方法计算和测定了马氏体型BT23钛合金的β转变温度,对比分析了化学成分计算法、组织分析计算法、差热分析法和连续升温金相法4种方法计算和测定β转变温度的效率和可靠性,以期获得一种高效、可靠且更适合测定马氏体型BT23合金β转变温度的测试方法。实验结果分析表明:连续升温金相法测定相变点为898℃,结果直观精确,但实验周期长;组织分析计算法所得相变温度为901.74℃,差热分析法测定的值较金相法略高,为903.1℃,此2种方法准确性高,检测效率高;化学成分计算法所得相变温度较金相法测定值高,仅可作为参考。     

含钌钛合金及其性能和应用

应用扫描电镜、电子探针、Ｘ射线衍射、低温拉伸及电阻法等分析技术，研究了５种Ｔｉ－Ｎｉ－Ｎｂ形状记忆合金的组织、相变特性和应变恢复率。结果表明：随着Ｔｉ－Ｎｉ－Ｎｂ合金中铌含量的增加。β－Ｎｂ相的体积分数增加，Ｍｓ温度和应变恢复率降低，而相变温度滞后变化不大。为获得较宽的相变温度滞后和高的应变恢复率，Ｔｉ－Ｎｉ－Ｎｂ合金的铌含量应控制在８ａｔ％￣９ａｔ％之间。     

合金成分对Ti－Ni－Nb合金相变特性及形状记忆效应的影响

应用扫描电镜、电子探针、Ｘ射线衍射、低温拉伸及电阻法等分析技术，研究了５种Ｔｉ－Ｎｉ－Ｎｂ形状记忆合金的组织、相变特性和应变恢复率。结果表明：随着Ｔｉ－Ｎｉ－Ｎｂ合金中铌含量的增加，β─Ｎｂ相的体积分数增加，Ｍ＿ｓ温度和应变恢复率降低，而相变温度滞后变化不大。为获得较宽的相变温度滞后和高的应变恢复率，Ｔｉ－Ｎｉ－Ｎｂ合金的钥含量应控制在８ａｔ％～９ａｔ％之间。     

Synthesis of metallic glass composites using phase separation phenomena

Phase separation phenomena in metallic glass systems have been explored by thermodynamic calculation and experimental method in the present study. Miscibility gap and spinodal curve for liquid phase in Gd–Ti–Al–Co/Cu systems have been calculated using the CALPHAD method. Based on the calculation result, various types of phase separation phenomena have been observed experimentally. Basically two types of structure are observed: interconnected-type structure by spinodal decomposition; and droplet-type structure by nucleation and growth mechanism. Multi-step phase separation occurs during cooling from the liquid, forming a hierarchical length scale composite structure. Depending on the glass-forming ability of the separated liquid phase, amorphous/amorphous or amorphous/crystalline composite structure can be obtained. The present study shows that there are several factors such as critical temperature, asymmetry and composition range of the spinodal curve which affect scale and morphology of the microstructure after phase separation.     

Magnetic-induced tricritical point in alloys and the low-temperature Fe−Ni and Fe−Ni−Cr phase diagrams

Phase equilibria at temperatures above and below the tricritical point of binary alloys are discussed in terms of thermodynamic principles. The existence of a second spinodal curve for the disordered phase within the magnetic-induced miscibility gap is rationalized. The relative interplay of the chemical and magnetic contributions to the stabilities of various types of phase equilibria in binary alloys is also discussed. The effect of magnetic contribution to the Fe?Ni and Fe-Ni-Cr phase stabilities at low temperatures is reviewed. The calculated phase diagrams of the Fe?Ni and Fe-Ni-Cr systems considering the magnetic and nonmagnetic terms are compared with experimental results. These results were obtained either from meteorites or from synthesized alloys subjected to irradiation. The meteorites, which have cooled slowly in space, may have achieved metastable/stable equilibrium conditions. The many defects introduced by irradiation for the synthesized alloys may have helped to achieve metastable/stable equilibrium conditions.     

Self-organized layered growth phenomena of diffusion couples with spinodal decomposition in binary alloys

In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition, a phase field model combined with elastic strain field was employed. Microstructure evolutions of diffusion couple with spinodal decomposition in binary alloys were numerically simulated by considering concentration fluctuation and elastic anisotropy. The simulation results indicate that the number of the periodical layers decreases with the increase of initial concentration fluctuation, even with large elastic anisotropy. The growth of layered microstructures can be attributed to the directional diffusion enhanced by initially discontinuous chemical potential at the interface.     

PCrNi3MoV钢静态CCT曲线的测定与分析

在Gleeble-1500D热模拟试验机上,利用膨胀法测定了PCrNi3MoV钢在不同冷却速度下过冷奥氏体连续冷却时的膨胀曲线。采用切线法获得了其相转变点,用Origin软件绘制PCrNi3MoV钢过冷奥氏体连续冷却相转变曲线(CCT曲线)。结果表明:PCrNi3MoV钢的临界点:Ac1和Ac3分别为720℃和850℃;Ms和Mf分别为300℃和160℃。对于过冷奥氏体,当冷却速度较慢时,如0.05~0.07℃/s时主要发生铁素体、贝氏体和马氏体转变;而冷却速度中等时,如0.1~1℃/s时发生贝氏体和大量马氏体转变;当冷却速度较大时,如50℃/s时只发生马氏体转变。随着冷却速度的增加,维氏硬度从500 HV迅速增加,当冷速大于1℃/s以后趋于平稳并达到800 HV。     

Co-Pt合金中L10原子间相互作用势和沉淀过程的微观相场法研究

本文基于微观相场法和原子间相互作用势方程,计算出Co-Pt合金中L10结构第一近邻原子间相互作用势,计算结果得到Co-Pt合金中L10结构第一近邻原子间相互作用势随温度增大而增大,随浓度增大而增大,且计算得到的随温度和浓度变化的原子间相互作用势与之前的实验值符合较好。利用计算的原子间相互作用势模拟了Co-Pt合金沉淀过程以及最终形貌,模拟结果能得到L10和L12结构,根据序参数可以得到L10结构的沉淀转变机制特征是失稳分解,而后粗化长大且最终两相体积分数接近,合金沉淀形貌与实验结果符合。相场法计算Co-Pt合金中L10结构原子间相互作用势,拓展了相场法在含L10结构的合金设计中的应用范围。     

The application of rational approximation in the calculation of a temperature field with a non-linear surface heat-transfer coefficient during quenching for 42CrMo steel cylinder

The calculation of a temperature field has a great influence upon the analysis of thermal stresses and stains during quenching. In this paper, a 42CrMo steel cylinder was used an example for investigation. From the TTT diagram of the 42CrMo steel, the CCT diagram was simulated by mathematical transformation, and the volume fraction of phase constituents was calculated. The thermal physical properties were treated as functions of temperature and the volume fraction of phase constituents. The rational approximation was applied to the finite element method. The temperature field with phase transformation and non-linear surface heat-transfer coefficients was calculated using this technique, which can effectively avoid oscillationin the numerical solution for a small time step. The experimental results of the temperature field calculation coincide with the numerical solutions.     

稀土对30CrMnSi铸钢TTT曲线的影响

研究了稀土对 30 Cr Mn Si铸钢 TTT曲线及相变点的影响 ,其结果为开始转变曲线右移 ,终了转变曲线左移 ,相变临界点滞后 ,Ms点升高     

加热速率对CuAlBe形状记忆合金相变的影响

通过差示扫描量热技术研究了不同的加热速率对CuAlBe形状记忆合金的相变特征的影响。结果表明：在不同加热速率下的相变点在一个区域内变化（Ms=120-128℃,Mf=99-105℃,As=142-130℃,Af=151-141℃）。快速加热使两个相变峰靠近,随着加热速率的降低,两个相变峰逐渐分离。用超低降温速率法分离后的DSC曲线,右瑞的大峰变为了一连串由许多微区依次发生马氏体逆相变所产生的许多小的放热峰。     

二元合金溶体两相平衡的巨势法计算

根据亚正规溶体模型,利用有效化学势及巨势相等的两相平衡条件,建立一种二元合金相平衡计算的新方法,与求自由能极小值的最优化方法相比,此法计算简单,不存在任何收敛性问題。