【作者】 张扣山；

【导师】 司乃潮；

【作者基本信息】 江苏大学 ， 材料加工工程， 2006， 硕士

【摘要】 物质就其排列方式来说，可以划分为晶体和非晶体。非晶态合金由于其长程无序短程有序的原子排列方式，与晶态合金相比，具有许多独特的物理与化学性质。因而块体非晶合金的研究是当前国际材料领域的前沿课题。本文利用在空气中普通铜模浇注法制备了块体Mg基非晶态合金及非晶复合材料，同时对非晶态合金进行了等温退火处理，采用差示扫描量热分析（DSC）、X射线衍射分析（XRD）、扫描电镜分析（SEM）及光学显微镜分析（OM）等手段对其进行了研究。本文首先研究了Zn元素对Mg₆₅Cu_25-xZn_xY₁₀（x=3，5，7）四元Mg基非晶合金的玻璃形成能力、晶化行为及熔化行为的影响。研究表明：当x=5时，合金的非晶形成能力最强，采用楔形铜模浇注完全非晶态试样厚度尺寸最大可达3.5mm，非晶形成的临界冷却速率为81.6K／s，同时玻璃转变温度和初始晶化温度最低，但约化玻璃转变温度T_rg最大，为0.583；而当x=3时，合金具有最大的热稳定性，合金的过冷液相区最宽，ΔT_x为63.8K。与其它合金相比较，Mg₆₅Cu₂₀Zn₅Y₁₀四元合金的晶化转变更为复杂，表现为明显的四级晶化过程，而其熔化曲线为单一的吸热峰。当用5％（原子百分比）的Nd元素部分替代Mg₆₅Cu_25-xZn_xY₁₀（X=3，5）合金中的Y元素后，合金的玻璃形成能力明显提高，能制得的完全非晶态试样最大尺寸分别为4.5mm和4mm，临界冷却速率分别为49.4K／s和62.5K／s。同时，Mg₆₅Cu₂₂Zn₃Y₅Nd₅非晶合金的晶化行为表现为明显的三级晶化，熔化曲线表现为较窄的单一吸热峰，峰宽为17.6℃。相比于Mg₆₅Cu₂₀Zn₅Y₁₀四元非晶合金，Mg₆₅Cu₂₂Zn₃Y₅Nd₅五元非晶合金的玻璃转变温度和初始晶化温度均明显提高。对Mg₆₅Cu₂₂Zn₃Y₅Nd₅非晶合金进行等温退火处理后，发生了非晶态向晶态的转变，原本单一非晶峰上出现了晶体相对应的尖锐晶体峰。在448K下，等温处理30min后，合金的脆性最大；在稍高温度468K下，等温处理30min后，合金的组织较为粗大，但脆性有所降低；而采用448K，15min+468K，15min分步晶化工艺处理后，合金组织均匀细小，同时具有最大的显微硬度，均值达到了268.2Hv，比完全非晶态下高出约41Hv。本文还制备了两种成分的金属玻璃基复合材料(Mg₆₅Cu₂₃Al₂Y₁₀和Mg₆₅-Cu₂₀Al₅Y₁₀)试样。XRD分析表明，随着Al元素的加入，原本的非晶”馒头峰”上出现了晶体增强相的尖锐峰；DSC曲线中晶化放热峰表明两种合金基体为非晶态结构，相比于纯玻璃态时，复合材料的玻璃转变温度和初始晶化温度均下降，过冷液相区变窄，同时表现为多级晶化；尽管两种合金的成分只有细微差别，但两者的微观组织却相差很大，当Al含量为2％时，显微组织中有明显的针状组织存在，而Al含量为5％时，为粒状组织，直径约100nm左右。此外，Al含量为5％时，复合材料的显微硬度只比非晶态下稍微有所增大，而Al含量为2％时，硬度值却明显提高，均值达到了285.6Hv，比完全非晶态下的硬度值高出了59.8Hv，同时相比于完全非晶态，复合材料无明显脆性。更多还原

【Abstract】 Materials can be classified into distinct species: crystal and amorphous body due to the ranging mode of atoms. Compared with crystalline alloys, amorphous alloys have many unique physical and chemical properties because of the short-range orders and long-range random packing mode of the atoms. The investigation on such bulk amorphous alloys has been the foreland of current domain of international materials. The Mg-based amorphous alloys and amorphous composites are prepared by a method of melt casting into copper mould in the air. And some of the bulk Mg-based amorphous alloys are heat-treated with isothermal annealing technics. All of the material are studied by the method of DSC, XRD, SEM, OM and so on.In this thesis, the effects of Zn on the glass-forming ability, crystallization behavior and melting behavior of Mg₆₅Cu_25-xZn_xY₁₀（x=3, 5, 7） alloys were studied first. With the x=5, glass-forming ability of the alloy was the best, Metallic glass strip with a thickness of 3.5 mm by the copper wedge mould was obtained, with the critical cooling rate 81.6K/s. At the same time, the glass transition temperature and the onset temperature of primary crystallization were the lowest, but the T_rg was the greatest, about 0.583. For x=3, the alloy has the best thermal stability, with the largest supercooled liquid region about 63.8K. Compared with other glass, the quaternary Mg₆₅Cu₂₀Zn₅Y₁₀ glass exhibits a more complex crystalliztion process, performed through four steps. But the melting, curve is a simple endothermic peak.The glass-forming ability is improved obviously, with the 5%（at） Y of Mg₆₅Cu_25-xZn_xY₁₀（x=3, 5） alloys substituted for Nd. Metallic glass strip with thickness of 4.5mm and 4mm can be obtained, with the critical cooling rate about 49.4K/s and 62.5K/s. The crystalliztion behavior of Mg₆₅Cu₂₂Zn₃Y₅ Nd₅ amorphous alloy shows a three-step process, and the metling process exhibits a narrow endothermic peak, about 17.6℃. Compared with the quaternary Mg₆₅Cu₂₀Zn₅Y₁₀ amorphous alloy, the glass transition temperature and the onset crystallization temperature of Mg₆₅Cu₂₂Zn₃Y₅Nd₅ amorhous alloy increase. With the isothermal treatment, the Mg₆₅Cu₂₂Zn₃Y₅ Nd₅ alloy transits from the amorphous state to the crystal state, and the sharp crystal peaks superimose on the simple amorphous peak. At the 448K, isothermal treated for 30min, the alloy has the largest brittleness; Treated at a higher temperature 468K, the microstructure of the alloy which has a lower brittleness is bigger compared with the others; Annealed the alloy step by step（448K, 15min+468K, 15min）, the microstructure of the alloy changed more homogeneous and smaller. And the average microhardness is 268.2Hv, which exceed about 41Hv than the metallic glass.Mg₆₅Cu₂₃Al₂Y₁₀ and Mg₆₅Cu₂₀Al₅Y₁₀ metallic glass matrix composites is prepared in this subject. With the addition of Al, the sharp peaks from reinforced crystal-phases superimposed on the broad, diffuse scattering maxima from amorphous matrix. The glass transitting-stag eand crystallization exothermic peaks in DSC graph show that the matrix were glass-state. Compared with the metallic glass, the glass transition temperature T_g and the onset temperature of primary crystallizationT_xl of composites were reduced, with the supercooled liquid region narrowing. And the maxtrix of composites show a more complex crystalliztion process. Although the compositional difference of the alloys is very samll they show essentially different microstructure. For Mg₆₅Cu₂₃Al₂Y₁₀ alloy, needle-shape phases can be observed, but grain structure（about 100nm） formed in Mg₆₅Cu₂₀Al₅Y₁₀alloy. The average microhardness of Mg₆₅Cu₂₃Al₂Y₁₀ is 285.6Hv, which exceed 59.8Hv than the metallic glass. Compared with the amorphous alloys, the composites show a non-evidentbrittleness.更多还原