GA镀层微观组织及转变机制研究现状

对GA镀层微观组织和在合金化过程中镀层微观组织转变进行了综述.重点论述了抑制层形成、组成和与钢基体之间晶体学相位关系等,以及镀层中Fe-Zn相的形成、晶体结构等,最后对合金化过程中三种典型的镀层微观组织转变特点进行了论述.     

双辊铸轧AZ31镁合金成形过程组织演变的研究

为了研究镁合金双辊铸轧过程微观组织的演变,对轧制试样进行了微观组织分析。利用有限元软件进行了熔池温度场、流场三维耦合数值模拟。探讨了镁合金铸轧过程熔池的特点及薄带的形成机理,并分析了双棍铸轧过程的动态组织演变。     

挤压铸造铝合金铸件内部温度测量及组织特征

开发了一种挤压铸造过程直接测量铸件内部温度的方法,该方法能够对直接挤压铸造过程中铸件内部的温度变化进行连续多模次测量。采用该方法,对A356铝合金挤压铸造过程中铸件内部温度变化进行了测量,获得了不同挤压压力下阶梯试件不同部位的冷却曲线。采用光学显微镜对测温部位附近的凝固组织进行了观察,并测量了晶粒尺寸。通过将凝固组织与冷却曲线对照分析,研究了压力对凝固组织的影响。     

TA11合金叶片挤杆过程中微观组织的数值模拟

将TA11合金的微观组织模型写入DEFORM-3D软件的用户子程序中,使其具备了对TA11合金热成形过程中微观组织的预测及模拟功能,并通过对圆柱体镦粗过程的模拟验证了程序的可靠性。以TA11合金叶片的挤杆过程为研究对象,对其微观组织变化进行数值模拟,研究了变形工艺参数对变形过程中微观组织变化的影响。结果表明,合适的变形速度、变形温度和压下量可以使晶粒细化,组织分布均匀,从而提高锻件的力学性能。     

17Cr2Ni2Mo齿轮轴淬火过程的数值模拟研究

利用Deform热处理模块对17Cr2Ni2Mo齿轮轴淬火加热、冷却过程的温度场、组织场和应力场进行了数值模拟,分析了加热过程中温度、组织和应力的变化以及淬火加热、冷却过程中存在的应力风险,并采用等比例的齿轮轴模型进行了淬火加热、冷却过程的测温实验,在齿根位置和中心位置套棒进行金相组织分析,结果表明,齿轮轴加热、冷却的温度、组织的计算机模拟结果与实测结果吻合较好,模拟结果对于产品制造工艺的制定有很好的指导作用。     

面向微观组织优化的锻造工艺预成形优化设计及实验研究

以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了锻造成形过程微观组织优化目标函数,并确定锻造成形预成形形状作为优化过程的设计变量。采用遗传算法和有限元模拟相结合的方法,开发了锻造过程微观组织优化程序,对典型的H型锻件进行了面向微观组织优化的预成形设计,取得了较好的效果。并根据优化设计的结果进行了实验研究,优化结果的晶粒尺寸及其分布趋势与实验结果比较吻合。     

面向微观组织优化的锻造工艺预成形优化设计

以锻件晶粒尺寸细小均匀为目标,以预成形形状设计为对象,提出了锻造成形过程微观组织优化设计方法,构建了锻造成形过程微观组织优化目标函数,并确定锻造成形预成形形状作为优化过程的设计变量,给出了优化设计的具体步骤,采用微观遗传算法和有限元模拟方法开发了锻造过程微观组织优化程序,并对典型的圆柱体镦粗进行了面向微观组织优化的预成形设计,取得了较好的效果.     

不锈钢/碳钢双金属复合板开裂过程研究

对不锈钢/碳钢冶金复合板开裂过程进行了分析,找到了复合板冶金结合中的薄弱组织,并对该组织进行了化学成分分析,对瞬间液相复合工艺进行改进,提高了双金属复合板的冶金结合强度。     

多元合金激光增材制造凝固组织演变模拟

针对多元合金激光熔覆过程,基于有限元方法和元胞自动机技术建立了多元合金激光熔覆熔池三维传热传质及凝固组织形貌演变模型,通过自行开发的宏微观耦合接口程序实现了三维熔池模型和多元合金凝固组织演变模型的耦合. 针对IN718激光熔覆过程中的传热传质和凝固组织演变过程进行了模拟,研究了基板初始晶粒尺寸、异质形核及多层熔覆扫描路径对熔覆层凝固组织形貌的影响机理,并对模拟结果进行了试验验证. 结果表明,模拟结果与实际物理过程吻合较好,所开发的耦合模型能够真实反映多元合金激光熔覆过程.     

金属凝固组织形成的仿真研究

利用Ｍｏｎｔｅ－Ｃａｒｌｏ方法,依据对金属凝固过程的温度场,浓度场的数值模拟和金属结晶过程中的热力学条件,建立了描述金属凝固组织形成过程的宏观－微观耦合模型,对Ａｌ－４．５％Ｃｕ（质量分数）固溶型合金的凝固组织形成过程进行了模拟,结果与实际凝固组织接近。     

法兰轴热锻过程中的微观组织演变的数值模拟

阐述了金属材料塑性加工中微观组织演变数值模拟的重要性。重点介绍了金属热锻过程中材料微观组织演变的机理和数学模型。完成了金属材料热变形过程中再结晶动力学与晶粒长大模型研究,编制用户子程序并嵌入到DEFORM-TM程序中。通过法兰轴的热锻过程中微观组织演变的实例,有效地验证了程序的可行性,对金属热锻过程微观组织预测有一定的指导作用。     

The effect of strain on dynamic recrystallization of PM Ti–45Al–10Nb intermetallics during isothermal forging

The strain in different regions of the pancake was different during isothermal forging process. Different strain could greatly influenced the forged microstructure. In the present work, the relationships between strain, dynamic recrystallization (DRX) and microstructure in different regions of powder metallurgy Ti–45Al–10Nb alloy during isothermal forging were investigated. The results show that the microstructure from the center to edge of the forged pancake was inhomogeneous due to the degree of DRX. And DRX was related with the degree of strain, large strain can promote DRX.     

热处理对TiC_p/Fe复合材料组织和性能的影响

研究了热处理对液态等温反应合成的TiCp/Fe复合材料的组织和性能的影响。指出热处理可以使在凝固过程中产生的少量TiFe2 和Fe3 C等相溶解消失 ,并得到一定数量的细小的二次TiC增强相。热处理过程能完全改变复合材料的基体组织。通过不同的热处理工艺 ,可以获得具有不同基体组织的复合材料 ,合金元素钼可有助于基体组织的调整。热处理过程对复合材料的性能也有较大的影响 ,二次TiC对基体的强化作用使复合材料的抗拉强度上升和冲击值下降     

Effect of initial microstructure on strain-stress partitioning and void formation in DP980 steel during uniaxial tension

Finite element analysis (FEA) was conducted to capture the effect of the initial microstructure on strain-stress partitioning and void formation in DP980 steel during uniaxial tension. By using the technique of direct mapping of a filtered microstructure into finite element meshes, FEA can capture the heterogeneity of strain-stress partitioning in DP980 steel through the thickness direction during uniaxial tension. The damage characteristics were studied through scanning electron microscope observations of polished sections of failed tensile specimens. FEA was also used to reveal the effect of microstructure heterogeneity on the hot spots for void formation during uniaxial tension.     

Microstructure evolution during warm working of Ti–6Al–4V with a colony-α microstructure

A high-resolution electron backscatter diffraction technique was employed to investigate microstructure evolution during warm working of Ti–6Al–4V with a colony-α microstructure. Particular emphasis was paid to the specific mechanisms governing this process. Microstructure development was found to be driven mainly by the geometrical requirements of the imposed strain and by the kinking of α lamellae. For the most part, the lamellar microstructure was surprisingly stable during straining, with limited globularization observed only in kinked α colonies. The kinking process was shown to be closely linked with the development of shear bands within the colonies. These observations suggest that changes in strain path may be beneficial in promoting globularization during warm working.     

薄板连铸连轧组织性能控制的现状与展望

分析了薄钢板生产过程中组织性能控制的特点和意义、国内外研究现状，并重点分析了薄板坯连铸连轧过程中的工艺与相变特征、连铸连轧过程中纳米级析出物及其对性能的影响以及组织细化与强化，对今后的发展进行了展望。     

INFLUENCING FACTORS FOR OBTAINING ULTRAFINE AUSTENITE GRAINS WITH INITIAL MICROSTRUCTURE OF WARM-ROLLED FERRITE/PEARLITE

Three warm-rolled ferrite/pearlite microstructures were prepared by rolling at 500℃, and the austenitizing characteristics were discussed in conjunction with deformation during the heating stage. The results indicated that the final austenite grain size was sensitive to the deformation direction of the initial warm-rolled microstructure. The transient microstructure at a given temperature was the most important influencing factor on the austenitizing characteristic combined with deformation. Moreover, the hot-rolled mierostructure also had to be prepared in an optimal state because of its direct effect on the warm-rolled microstructure.     

Microstructure Characteristics in Ultrafine-grained Commercially Pure Aluminium after Laser Shock Processing

The aim of this paper was to address the effect of laser shock processing (LSP) on the microstructure of ultrafine-grained commercially pure aluminium which was produced through severe cold rolling and annealing. The microstructure characteristics of ultrafine-grained commercially pure aluminium were experimentally investigated by TEM during ultra-high strain rate loading. The results show that microstructure was obviously refined due to ultra-high plastic strain induced by a single pass LSP impacts. The gr...     

Simulation of Microstructure for Hot Pack-Forging of a High Nb Containing TiAl Alloy

利用Deform-3D软件对高铌TiAl合金包套锻造过程中的微观组织演变进行模拟。为得到模拟所需参数,在1100～1250℃和0.001～0.5 s-1的条件下对合金进行了热压缩试验。在所得试验数据的基础上,利用一种间接方法建立了合金的动态再结晶模型,并利用Avrami形式的方程对再结晶分数进行描述。采用Cingara硬化模型及所建立的再结晶分数模型构建了合金的流变应力本构模型。模拟结果显示,由于锻造过程中摩擦的存在、热量的损失以及简单单向镦粗变形的锻造方式,使得坯料中的微观组织分布不均匀。通过模拟结果与实验结果的比较,证明所建立的有限元模型能够有效地预测高铌TiAl合金在包套锻造过程中的组织演变。     

Evolution of microstructure and electrical resistivity of Cu–12wt.%Ag filamentary microcomposite with drawing deformation

Cu–12wt.%Ag filamentary microcomposite was prepared by heavy cold drawing. The microstructure was observed and the electrical resistivity determined at different strain levels. The mechanism responsible for the electronic conduction was discussed according to the microstructure evolution during drawing deformation.