混合稀土基大块非晶合金的制备及力学性能

用铜模铸造法成功制备出直径为3 mm以混合稀土金属Mm(Mischmetal)为基的成本较低的Mm55Al25Ni10Cu5Co5大块非晶合金。利用XRD和DSC等手段对该合金的形成能力及热稳定性进行了分析。结果表明,该合金具有很好的非晶形成能力及热稳定性(明显的玻璃转变温度Tg、宽的过冷液相区ΔTx(=Tx-Tg)>60 K及高的约化玻璃转变温度Trg(=Tg/Tm)>0.67).同时,该合金的压缩断裂强度(σf)为676 MPa,比La55 Al25Ni10Cu5Co5大块非晶提高94 MPa.     

Fe_(40)Co_(40)Zr_(10)B_9M_1(M=Cu,Ge,Ag)合金的热稳定性及微观结构研究

采用单辊快淬法制备Fe40Co40Zr10B9Cu1、Fe40Co40Zr10B9Ge1和Fe40Co40Zr10B9Ag1非晶合金薄带,并对3种合金在不同温度下进行热处理.利用差热分析仪(DTA)和X射线衍射仪(XRD)等测试手段对样品的热稳定性及微观结构进行研究.结果表明:Fe40Co40Zr10B9Cu1、Fe40Co40Zr10B9Ge1和Fe40Co40Zr10B9Ag13种合金的激活能分别为262.4、267.6和252.3 k J/mol,说明Cu元素、Ge元素和Ag元素的添加对合金的热稳定性影响不大,Ge元素的添加最有利于提高合金的热稳定性.3种合金的晶化过程相似:非晶→非晶+α-Fe(Co)→α-Fe(Co)+Zr Co3B2+Fe(Co)3Zr.     

稀土元素对Cu基非晶合金形成能力和力学性能的影响

通过铜模铸造法成功制备出直径分别为5 mm和3 mm的三元Cu45Zr48Al7和四元Cu45Zr45Al7Y3大块非晶合金。采用甩带法制备了Cu42Ni8Ti48Sm2、Cu42Ni8Ti48Y2、Cu42Ni8Ti48Gd2三种条带非晶;其中,Cu42Ni8Ti48Y2合金的非晶形成能力最强。三种非晶的玻璃转变温度Tg不十分明显,在冷却过程中存在着一定浓度的初晶相预存核,过冷液相区ΔTx不能反映该合金系非晶形成能力的差异。Cu47Zr42Al6Y5和Cu47Zr42Al6Er5合金组织基本由非晶相组成;Cu47Zr42Al6La5合金组织含有较多的晶态相,其压缩断裂强度较低;压缩断裂机理为解理 穿晶。     

Cu—Zr—Al大块非晶合金的制备及性能研究

采用铜模铸造的方法制备了Cu48Zr52-x Alx（x=6,7,8,9,10,at％）几种合金奠射线衍射（XRD）实验检验Cu48Zr44Al8,Cu48Zr43Al两种合金样品为完全非晶态．对样品进行差示扫描量热分析（DSC）考查三种大块非晶合金的非晶形成能力,以及灿的添加对非晶形成能力的影响．结果表明：当铝含量X=9时,合金的非晶形成能力及热稳定性最好．     

元素Ce对Y基合金非晶形成能力和热稳定性的影响

采用铜模吸铸法成功制备出直径为3 mm的Y56Al24Ni20和直径为5 mm的Y36Ce20Al24Ni20大块非晶合金,用X射线衍射法和差示扫描量热法对其非晶形成能力及热稳定性进行了分析。结果表明:Y36Ce20Al24Ni20大块非晶合金存在明显的玻璃转变温度Tg,其过冷液相区温度宽度ΔTx=63 K,约化玻璃转变温度Trg=0.70 K。这说明稀土元素Ce可以改善Y56Al24Ni20合金的非晶形成能力及热稳定性。     

钇对ZrCuNiAl系合金非晶形成能力的影响

利用X射线衍射（XRD）和差示扫描量热分析（DSC）研究了添加钇对Zr55 Cu30Ni5Al10Y（=0,1,2,3,4）非晶合金体系玻璃形成能力的影响。用铜模铸造获得的Zr55-xCu30Ni5Al10Y（=0,1,2,3,4）块体非晶合金的临界尺寸从直径6 mm增加到20 mm。分析认为,微量钇的添加可以与合金中的残留氧形成氧化物,降低氧对合金形成非晶态结构的负面效应。因此添加适量的稀土元素钇有利于提高Zr55 Cu30Ni5Al10Y非晶合金体系的玻璃形成能力。     

添加微量稀土钇对铜基合金非晶形成能力的影响

针对铜基非晶合金玻璃形成能力问题,分析了添加微量稀土元素Y对合金的玻璃形成能力、热稳定性的影响,利用铜模吸铸法制备出Cu-Zr-Al-Y9mm非晶合金.研究结果表明：制备的9mm铜基非晶合金试样（Cu45Zr47Al8）97Y3,在过冷液相区ΔT和约化玻璃转变温度Trg分别是79.42K和0.775 3.随着稀土元素Y含量的增加Trg值变小,合金的非晶形成能力降低,通过Trg值变化可以判别该合金的非晶形成能力.     

Fe对Zr55Al10Ni5Cu30非晶形成能力及力学性能的影响

为了进一步提高锆基大块非晶合金的玻璃形成能力及力学性能,采用铜模吹铸法制备了（Zr0.55Al10Ni0.05Cu0.30）100-xFex（X=1,5,10）系列合金,通过X射线衍射（XRD）、差示扫描量热法（DSC）以及压缩实验和SEM进行材料分析。研究表明：微量Fe有助于改善非晶合金在压缩变形时剪切带内的应力分布,提高材料的综合性能,当Fe添加量为1％时,塑性应变εp达到5．9％,强度达到1．89GPa,同时,随着Fe添加量的增加,过冷温度区间ΔTx减小,热稳定性减小,非晶形成能力降低。     

工业原料制备Zr-Cu基非晶合金及其压缩断裂行为研究

采用工业原料制备了Φ4 mm的Zr55Cu30Ni5Al10非晶合金棒材,利用XRD,DSC,SEM分析了该合金体系玻璃形成能力及压缩断裂行为.结果表明:Zr55Cu30Ni5Al10非晶合金棒材在10,15,20 K/s的升温速度下,过冷液相区△Tx分别为71.2,72.4,68.1 K,具有较大的玻璃形成能力.该非晶合金棒材抗压强度达到1 702 MPa,断口微观形貌为典型的脉络状花纹,在断口与试样连接处发现大量的剪切带存在,同时还产生了局部熔化现象.     

Fe-B-Nb-Er块状非晶合金的形成能力及热稳定性研究

采用工业原料通过铜模喷铸法制备了(Fe7.2B24Nb4)100-x Er x(x=3.0、4.0、4.5、5.0、6.0、7.0)块状非晶合金系,采用X射线衍射仪、DSC差示热量扫描仪研究了稀土元素Er对该非晶合金系热稳定性、玻璃形成能力的影响.结果表明:稀土元素Er的添加明显提高了样品的非晶形成能力,Er含量(摩尔分数)为5.0%时成功制备出直径为5 mm的(Fe72B24Nb4)95Er5块状非晶,该非晶合金具有较高的热稳定性,抗晶化能力较强,其晶化激活能分别达到382.8、539.5、680.8 kJ/mol.     

Corrosion Behavior of Mg65Cu25-xZnxGd10 (x=0, 5) Metallic Glass

The effect of substitutional element Zn on corrosion behavior of Mg65Cu25Gd10 glass was investigated. The amorphous structure of Mg65Cu25-xZnxGd10(x=0, 5) alloys were examined by X-ray diffractometry and differential scanning calorimetry (DSC). The dissolution rates of Mg65Cu25-xZnxGd10(x=0,5) metallic glasses in a 5 wt% NaCl solution with pH value of 7 were determined by a hydrogen evolution testing method. The corrosion behavior of these alloys was characterized using dipping tests with 5 wt% NaCl, in combination with electrochemical measurements and scanning electron microscopy (SEM). Results show that the anti-corrosion ability of Mg65Cu25Gd10 alloy is significantly improved due to the addition of Zn. Possible mechanism responsible for the improvement is discussed.     

EXAFS Studies on Local Atomic Structure in the Amorphous Mg_(65)Cu_(25)Gd_(10) Alloy

Local atomic structures of an amorphous Mg65Cu25Gd10 alloy and the structural changes by thermal annealing have been studied by extended X-ray absorption fine structure (EXAFS). The correlation between structural changes and mechanical properties for the Mg65Cu25Gd10 alloy has also been discussed. Results showed that Cu atoms around Gd in Mg65Cu25Gd10 lost rapidly during annealing , resulting in the segregation of Cu atoms. The coordination number NGd-Mg of Mg65Cu25Gd10 annealed at 373 K first diminished and then augmented with the increase of annealing time. The formation of polyhedral short-range order unit with coordination number of nearly 12 around Gd atoms is in favor of the improvement of mechanical properties. The chemical short-range order, not topological short-range order in the amorphous Mg65Cu25Gd10 alloy had obvious changes during annealing.     

锆基非晶合金在NaOH溶液中的腐蚀行为

用电化学极化曲线研究锆基非晶合金Zr53.5Cu26.5Ni5Al12Ag3在25℃和60℃温度下,在0.01 mol/L和0.1 mol/L的NaOH溶液中腐蚀100 h的腐蚀行为,并用金相显微镜和扫描电镜对腐蚀前后试样的表面形貌进行观察与分析.极化曲线的测试结果表明：锆基非晶合金在25℃下,在浓度为0.01 mol/L和0.1 mol/L的NaOH溶液中浸泡100 h,随着NaOH溶液浓度的升高,非晶合金的耐腐蚀能力下降;锆基非晶合金在25℃和60℃下,在浓度为0.01 mol/L的NaOH溶液中浸泡100 h,随着NaOH溶液温度的升高,非晶合金的耐腐蚀能力下降;锆基非晶合金和晶态合金在60℃下,在浓度为0.1 mol/L的NaOH溶液中浸泡100 h,非晶合金的耐腐蚀性能优于晶态合金.最后根据电化学腐蚀原理,从腐蚀介质温度和浓度方面的性质探讨锆基合金耐蚀性能的因素.     

Mg-Zn-Ca块体非晶合金及其强度可靠性

针对Mg-Ln-TM块体非晶合金脆性大、强度可靠性差等特点,研究了新型Mg-Zn-Ca非晶合金的性能并考察了成分变化对其热稳定性的影响。采用铜模铸造法制备出直径为2mm的Mg_70-xZn_25+xCa₅(x=1、2、3、4)系列非晶合金,利用扫描电镜(SEM)、X射线衍射仪(XRD)、差分扫描量热仪（DSC）以及电子万能试验机分别研究了铸态样品的组织、相结构、热稳定性以及力学性能。实验结果表明：该系列非晶合金的晶化过程分3~4步完成,初始晶化温度随Mg含量的提高而降低,同时对应较高的强度和一定的塑性应变。经Weibull统计分析表明：这4种非晶合金断裂强度的再现性存在差别,其中具有脉络纹断口的合金具有较高的Weibull模量,对应着良好的断裂强度再现性。     

Room temperature plastic deformation behavior of ZrCuNiAl bulk metallic glasses

The Zr62.55Cu17.55Ni9.9Al10 bulk metallic glass (BMG) was prepared by using copper-mold suction-casting. X-ray diffraction and differential scanning calorimetry were utilized to determine its structure and thermal stability. Uniaxial compression and Rockwell indenta-tion tests were adopted to study the plastic deformation behavior at room temperature. The results show that the glass transition temperature and the onset temperature of exothermic reaction of the BMG are 651.5 and 748 K, respectively. During the compression test, the BMGs undergo an engineering strain of about 2.5%, i.e., true strain of 2.8%, and then fracture. The BMGs deform via the formation and propagation of shear bands. Under indentation loading, the BMGs deform through the formation of radiation-like and circular shear bands. The circular shear bands form earlier than the radiation-like ones. The formation mechanism of shear bands in the BMGs was analyzed and discussed.     

Mg-Cu-Zn-Y-Zr bulk metallic glassy composite with high strength and plasticity

Mg₆₅Cu₂₀Zn₅Y₉Zr₁ bulk metallic glass matrix composite with a diameter of 2 mm was produced by copper mold casting. Upon cooling the Mg₆₅Cu₂₀Zn₅Y₉Zr₁ melt, Mg₂Cu acicular crystalline phase precipitates uniformly with a size of about 20 μm long and 1 μm thick while the remaining melt undergoes glass transition. Room temperature compression tests revealed that the high fracture strength up to 830 MPa and the plastic strain of 2.4% before failure are obtained for the Mg-based bulk metallic glass matrix composite. The formation of the Mg₂Cu phase was proposed to contribute to high strength and plastic deformation of the material.     

Effect of the repeated melting of mother ingot on the stability of icosahedral phase precipitated from Zr-Al-Ni-Cu-Ag glass

Since the icosahedral phase (I-phase) was first found in a rapidly solidified Al84Mn16 alloy by Shechtman et al.[1] in 1984, a lot of studies on I-phase have been carried out. The typical systems in which the icosahedral quasicrystals can be formed include Al-[2,3], Pd-[4] and Ti-based[5] ones. In most cases, the I-phase forms as metastable phase and its formation depends on the cooling rate. Later, precipitation of I-phase during the crystallization of Zr-based metallic glass was reported…     

Effects of small amount Ta on the characteristics ofthe Zr-Al-Ni-Cu-Ta bulk metallic glass

The effects of Ta on the characteristics of the Zr-base BMG (bulk metallic glass) were investigated. Zr55Al10Ni5Cu30-xTax(x=1,2,4) bulk metallic glasses (BMGs) with 3.5 mm diameter and 70 mm length were successfully prepared by using combined jet and copper mold casting. A small amount of Ta addition does not change the glass transition temperature, crystallization temperature, and supercooled liquid region obviously, but Ta promotes composition separation and two-stage crystallization. The stable crystalline phases include ZrENi, CuZr2, AlEZr3 intermetallic compounds and Ta-rich solid solution after annealing the Zr-Al-Ni-Cu-Ta alloys at 753 K. Zr55Al10Ni5Cu30-xTax (x=1,2,4) bulk glassy alloys exhibit a better compressive strength. The stress-strain curve shows a zigzag feature, and the fracture surface shows intersecting of shear bands. It may correlate with the inhomogeneous feature of amorphous structure.     

Effect of heat treatment on the mechanical properties of FeCoZrWB bulk metallic glass

A Fe61Co10Zr5W4B20 bulk metallic glass (BMG) with a diameter of 2 mm was prepared by using copper mould suction casting. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), micro-hardness and compression tests were adopted to investigate the structure, thermal stability, especially, the effect of heat treatment on the micro-hardness and compression strength of this BMG. The BMG exhibits micro-hardness of about 1 207 Hv and compression fracture strength of about 1 707.6 MPa. After being annealed below the onset of crystallization temperature, the micro-hardness almost keeps constant. But after being annealed above the peak of crystallization temperature, the micro-hardness increases firstly and then declines gradually with the elongation of annealing time. However, annealed for the same period of time, the micro-hardness will increase with the rise of annealing temperature, while the compression fracture strength will apparently decrease.