Microstructure and thermal expansion of copper-based amorphous alloys during structural relaxation

(Cu43Zr48Al9)98Y2 amorphous alloy bar was prepared by the arc melting copper mold absorption casting method,and then,the amorphous alloy was annealed at different temperatures for different times.The influence of heating rate on thermal expansion and thermal stability was studied by thermomechanical analysis(TMA),and the microstructure evolution of the amorphous alloy during structural relaxation and crystallization was studied by XRD and TEM.Results show that the structural evolution behavior of the(Cu43Zr48Al9)98Y2 amorphous alloy can be divided into five different stages(structural relaxation preparation stage,structural relaxation stage,first crystallization stage,second crystallization stage,and grain growth stage).When the heating rate is 20 K/min,the amorphous alloy has the smallest thermal expansion coefficient and the best thermal stability.The width of the supercooled liquid region is 66.42 K.Samples with different relaxation states were prepared by annealing at the heating rate of 20 K/min.The structural evolution of amorphous alloys with different relaxation states is as follows:amorphous→CuZr2+AlCu2Zr7→CuZr2+AlCu2Zr7+CuZr(B2)+CuZr(M)+Cu10Zr7→CuZr2+AlCu2Zr7+CuZr(B2)+CuZr(M).After annealing at 706 K and 726 K(in the supercooled liquid region)for 1.5 h,the amorphous-nanocrystalline composites were obtained.When the annealing temperature is 706 K,the crystallization process of the sample is as follows:amorphous→Cu10Zr7→Cu10Zr7+CuZr,and for the sample at 726 K,it is as follows:amorphous→CuZr2+AlCu2Zr7+Cu10Zr7→Cu10Zr7+CuZr2→CuZr2+CuZr(B2)+Cu10Zr7.

有机硅改性酚醛树脂的研究进展

硅元素因其优异的耐高温、富韧性、憎水性,被广泛用于无机-有机复合材料中,在酚醛树脂中的改性应用更成为了近些年研究的热点。阐述了含硅化合物改性酚醛树脂应用研究进展,主要介绍了硅改性酚醛树脂复合材料的微观形貌、热稳定性和机械强度,最后对其前景进行了展望。

大尺寸TiAl/Ti_3Al微叠层薄板制备与热稳定性研究

采用大功率电子束物理气相沉积(EB-PVD)制备了厚度为0.1-10 mm大尺寸薄板TiAl/Ti3Al叠层状复合材料。利用XRD和SEM对材料的组成相和微观结构进行了分析。实验结果表明:材料由α2-Ti3Al和γ-TiAl相组成,具有明显的层状结构,TiAl晶粒平均尺寸为1-2μm。通过真空热处理的方法考察了微叠层材料的在不同温度下保温3 h后的结构演变,并研究了微叠层材料层状结构的退化机理。

等原子比AlNiZrCuY高熵非晶复合材料的组织与耐腐蚀性能

利用真空电弧熔炼技术与急速冷却快淬设备制备了一种等原子比AlNiZrCuY高熵非晶复合材料薄带,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、差示扫描量热仪(DSC)、显微硬度计等手段表征了该复合材料的显微结构、相稳定性并测定其硬度;通过极化曲线和电化学阻抗谱等测试方法研究了高熵非晶复合材料室温下在模拟海水(3.5%NaCl水溶液,质量分数)中的防腐蚀性能。结果表明:Al_(2)0Ni_(2)0Zr_(2)0Cu_(2)0Y_(2)0高熵非晶复合材料是由非晶态组织与金属间化合物相共同组成;利用阿基米德排水法测得材料实际密度约为5.792 g/cm^(3);其维氏显微硬度(HV0.1)为4610 MPa,击破电位(E_(b))为–0.215 V,维钝电流密度(i_(pass))为29.44μA/cm^(2)。该高熵非晶复合材料在金属表面防腐与耐磨领域应用前景广阔。