MgAlLiZnTi轻质高熵合金的热变形行为与热加工图研究

采用Gleeble-3500热/力模拟试验机,在变形温度为250—350℃、应变速率分别为0.001、0.01、0.1和1 s^-1、真应变量分别为0.3、0.45、0.6的条件下,对Mg₅₄Al₂₂Li₁₁Zn₁₁Ti₂轻质高熵合金进行热压缩实验。基于Arrhennius模型对热压缩实验数据进行拟合,建立合金的本构方程,并绘制该合金在不同真应变下的热加工图。结果表明:在实验条件下,合金的热变形过程为加工硬化和动态再结晶为主的动态软化,且该合金的流变应力值与应变速率呈正相关,与变形温度呈负相关;该合金的热加工图表明,最佳的热加工工艺参数为变形温度335—350℃、应变速率1×10^-3—1 s^-1。     

生长速率对NiAl-43V(Dy)合金定向凝固组织的影响

用高温梯度定向凝固液态金属冷却技术(LMC,GL=310 K/cm)制备NiAl-43V-x Dy(质量分数x=0,0.05%)过共晶合金,研究定向凝固生长速率对两种成分合金固液界面形态和稳态区组织演变影响,同时对比研究微量Dy对NiAl-43V合金定向凝固组织的影响。结果表明:在6~150μm/s内两种合金固、液界面均为胞枝共存界面;两种合金凝固组织均由初生V相和共晶组织(片层V相+NiAl相)组成,随生长速率增大,合金凝固组织中枝晶析出增多,枝晶体积分数增大,共晶组织和枝晶得到细化。在NiAl-43V合金中加入质量分数为0.05%的Dy使Gibbs-Thompson系数减小,在相同生长速率下,微量Dy可使共晶层间距减小,溶质原子重新分配,枝晶尖端过冷度降低,枝晶体积分数减小,枝晶间溶质原子浓度增加使一次枝晶间距增大;微量Dy可抑制初生枝晶生长。     

车用铸态Ti-5.5Al合金热压缩变形行为研究

用铸态Ti-5.5Al-3.0Nb-3.0Zr-1.2Mo合金为基材,在Gleeble-3800D热模拟测试机上高温压缩测试,变形温度为750~900℃,变形速率为0.001~1 s^-1,总变形比例为75%。结果表明:应变提高,铸态合金加工硬化明显,流变应力呈直线增大;到达峰值应力后,组织开始软化,在软化与硬化过程达动态平衡时,获得稳定流变。处于低变形温度下,动态软化受应变率影响最明显,合金软化受变形温度与应变率共同作用。升温至850℃,存在动态再结晶现象,表现为动态回复。以较低应变率变形时,促进动态再结晶的快速完成,α相可促进动态再结晶转变。提高应变率后,合金中的β相软化机制由动态再结晶转变成局部塑性流变。     

Characterization of the hard anodizing layers formed on 2014-T3 Al alloy,in sulphuric acid electrolyte containing sodium lignin sulphonate

The properties of hard anodizing layers formed on 2014 Al alloy in sulphuric acid electrolyte containing sodium lignin sulphonate were investigated. The corrosion behavior of 2014 Al alloy has been studied using potentiodynamic polarization technique. Anodic layers morphology and composition were examined by scanning electron microscope, energy dispersion X-ray (EDX), X-ray diffraction (XRD) and Fourier infrared spectroscopy (FTIR). The results showed that the corrosion resistance has been enhanced after hard anodizing of 2014 Al alloy. Addition of lignin sulphonate to the sulphuric acid electrolyte significantly improved the corrosion resistance of the anodized 2014 aluminum alloy by adsorption on copper-intermetallic phases. Adsorption of sodium lignin sulphonate on oxide surface has been confirmed by SEM, EDX, and FTIR. Phenolic and carboxylic groups in sodium lignin sulphonate are functional groups, which are responsible of complex formation on oxide surface. The morphology of the hard anodizing layer is non-homogenous due to the high copper content of 2014 Al alloy. Addition of sodium lignin sulphonate resulted in the formation of anodic layers with more homogeneity and fewer cracks.     

金属材料对连续波红外激光的热耦合系数

我们采用自行设计研制的积分球,测量了几种不同表面状况的LY12铝合金靶对CWCO2激光(功率40W左右)的热耦合系数.与理想条件下的经典理论值相比,热耦合系数的测量值偏大,文中对此进行了分析.结果表明,材料的表面缺陷将增强对入射激光的热耦合.     

铝合金表面激光处理的三种工艺特点

表面重熔、表面合金化及表面熔覆是铝合金表面激光改质的三个主要方法,各方法都有自已的特点,但又有相关性.通过一系列实验可以对比性地了解这些工艺对铝合金表面组织的影响及强化效果,这将对铝合金激光表面强化新工艺的研究和应用提供参考.     

钛合金的激光气体氮化研究

本研究了Ｔｉ－６Ａｌ－４Ｖ合金的激光气体氮化，试验结果表明在激光功率密度大于５．０×１０＾４Ｗ／ｃｍ＾２，氮气压力为０．４ＭＰａ，通过激光辐射可在Ｔｉ－６Ａｌ－４Ｖ合金表面形成氮化钛。其氮化层的厚度为４００μｍ。在氮化层中存在大量氮化钛枝晶。其平均二次枝晶间距为１．７７μｍ。细小的氮化钛枝晶均匀地分布在氮化层中。最后测定和分析了氮化层的显微组织、相成份和显微硬度，并讨论了氮化钛的形成过程。     

Stress relaxation and creep in an impression test

A localized stress relaxation technique is described suitable for testing miniature structures and components. The actual size of the area that can be tested depends on the size of the indenter and the sensitivity of the load measurement device. However, the indenter should not be so small that macroscopic theory of deformation cannot be used. The technique described includes a quantitative treatment of the data which can be handled by a computer. Extensive data collection can be made so that many deformation parameters can be examined by using this simple test.     

Evolution of grain structure in thin film reactions

In this paper, we examine, both experimentally and theoretically, the kinetics of formation and microstructure of product phases in thin film reactions, using the Nb/Al and Ti/Al systems as our prototypes. The results of calorimetry and microscopy studies are interpreted using simple kinetic and morphology models. In particular, the kinetic models employed here focus on the nucleation and growth components of the phase formation process and the morphology models provide a starting point for the classification of product grain structures. An erratum to this article is available at .     

激光表面熔铸钴基合金涂层耐磨性的研究

研究了GH33高温合金表面激光熔铸钴基合金涂层对耐磨性的影响。磨损试验表明，熔铸层耐磨性较基体金属提高3倍以上，借助SEM、EMPA、X射线衍射等手段对复合涂层磨损机理进行了探讨。