Fe68Nd5Zr2Y4B21大块非晶合金磁性能的研究

采用铜模吸铸法制备出厚度为0.8 mm的片状Fe68Nd5Zr2Y4B21大块非晶合金.利用X射线衍射(XRD),差热分析(DTA)和振动样品磁强计(VSM)研究了Fe68Nd5Zr2Y4B21大块非晶合金在铸态和不同温度退火后的磁性能.结果表明,Fe68Nd5Zr2Y4B21大块非晶合金在铸态下为软磁性.合金晶化退火后,磁性能转变为硬磁性,得到了块状的纳米晶复合永磁材料.合金硬磁性的产生是由于合金晶化后产生了Nd2Fe14B硬磁性相和α-Fe,Fe3B软磁性相,软、硬磁相间产生了较强的交换耦合作用而造成的.这一方法为制备块体纳米晶复合永磁材料提供了一种新的手段.     

Cu44.25Ag14.75Zr36Ti5非晶合金的晶化行为

采用铜模铸造法制备了直径为3mm的柱状Cu44.25Ag14.75Zr36Ti5块体非晶合金,X射线衍射证明试样为完全非晶态。利用差示扫描热分析仪(DSC)、X射线衍射,研究了该非晶合金的晶化行为。利用Kissinger和Ozawa方程求得Cu44.25Ag14.75Zr36Ti5第一晶化峰和第二晶化峰的晶化激活能。结果表明,该大块非晶合金具有良好的热稳定性,在10K/min的加热速率下,析出相主要是Cu8Zr3和Cu10Zr7。     

Cu_(46)Zr_(47-x)Al_7Ti_x(x=0,1.5)非晶合金晶化动力学研究

采用铜模吸铸法制备Cu46Zr47-xA l7Tix(x=0,1.5)大块非晶合金。用X射线衍射仪(XRD)确定合金的结构,采用差示扫描量热仪(DSC)对非晶合金的晶化动力学进行了研究。结果显示,随着升温速率的加快,这两种非晶合金的玻璃转变温度Tg,晶化开始温度Tx和晶化峰值温度Tp均向高温区移动,且过冷液相区逐渐加宽,表明非晶合金的玻璃化转变和晶化均具有动力学效应。利用K issinger方程计算合金的晶化激活能。通过晶化动力学研究了热稳定性和晶化反应速率常数之间的关系,以及Ti元素添加对Cu-Zr-A l大块非晶合金热稳定性的影响。     

Zr-Ti-Cu-Ni-Be大块非晶合金等温晶化过程相分离研究

利用差示扫描量热法(DSC)和透射电镜(TEM)对Zr41.2Ti13.8Cu12.5Ni10Be22.5(at％)大块非晶合金的等温晶化过程和析出相进行了研究。结果表明，大块非晶合金在等温晶化过程中表现出多阶段相析出行为，并且在不同的晶化阶段，析出相也有所不同。在第1个晶化阶段，析出相主要是体心四方(b.c．t)结构的Zr2Cu相；而在晶化的第2个阶段，晶化相主要为简单六方结构的ZrBe2相。从一定程度上证实了Zr41.2Ti13.8Cu12.5Ni10Be22.5大块非晶合金在发生晶化时会形成富Zr区和富Be区，即有相分离的趋势。XRD测试的结果也证实了非晶合金在发生完全晶化时，主要的晶化产物为Zr2Cu和ZrBe2相。     

Co含量对FeCoZrB合金热性能、晶化过程及磁性能的影响

采用单辊快淬法制备(Fe1-xCox)76Zr9B15(x=0,0.25,0.5)非晶合金薄带,并对3种合金进行不同温度热处理。利用差热分析仪(DTA)、X射线衍射仪(XRD)和振动样品磁强计(VSM)研究3种合金的晶化行为、微观结构和磁性能。结果表明,Fe76Zr9B15、Fe57Co19Zr9B15和Fe38Co38Zr9B15合金的晶化激活能分别为363.50、434.86和536.33 k J/mol。Fe76Zr9B15非晶合金的初始晶化产物为Fe23B6型相和α-Fe相,Fe57Co19Zr9B15非晶合金的初始晶化产物为α-Mn型相和α-Fe(Co)相,Fe38Co38Zr9B15非晶合金的初始晶化产物为α-Fe(Co)相。随着热处理温度的增加,(Fe1-xCox)76Zr9B15(x=0,0.25,0.5)合金的矫顽力随各自晶化产物的不同而发生改变。     

块体非晶合金Zr45Cu48Al7激光焊接过程中晶化行为的研究

非晶合金作为一种异于晶态合金的金属材料,其受焊行为与晶态材料突出的区别在于非晶材料的晶化问题。采用了激光焊接技术连接块体非晶合金Zr45 Cu48Al7,研究了焊接过程中焊缝和热影响区的晶化行为。基于DSC实验结果,推导了块体非晶合金Zr45Cy48Al7晶化转变温度与加热速率立方根的正比关系,并将此结果应用于激光焊接加热过程中,进行了热影响区(HAZ)晶化体积的研究,分析了焊缝凝固后没有形成枝状晶的原因。     

差热分析实验条件对大块非晶合金Zr55Cu30Al10Ni5晶化行为的影响

研究了差热分析实验条件对大块非晶合金Zr55Cu30Al10Ni5晶化行为的影响,并结合X射线衍射研究其晶化后的物相.结果表明,大块非晶合金Zr55Cu30Al10Ni5的晶化分为两个转变过程,第一个转变过程对应的是非晶相的晶化,晶化相为具有Zr2Ni结构的亚稳相和少量的Al.Ni0.3Zr;第二个转变过程对应亚稳相向稳定相Zr2Cu的转变.在差热分析实验中,用Al2O3粉掩埋的样品在900℃以上还出现了第3个放热峰,这是样品与Al2O3粉发生化学反应所引起的,但在冷却过程中未出现两个结晶峰.     

Fe_(77)Co_4Zr_9B_(10)合金的热稳定性、微观结构和磁性能研究

采用单辊快淬法制备Fe77Co4Zr9B10非晶合金,在不同温度下对该合金进行热处理。利用差热分析仪(DTA)、X射线衍射仪(XRD)、原子力显微镜(AFM)以及振动样品磁强计(VSM)等手段对Fe77Co4Zr9B10合金薄带的晶化行为、微观结构和磁性能进行研究。结果表明:Fe77Co4Zr9B10非晶合金的晶化峰值温度Tp的晶化激活能Ep为525.19 k J/mol。Fe77Co4Zr9B10非晶合金在晶化初期,观察到α-Fe和α-Mn型晶化物析出;943 K退火,α-Mn型晶化物消失。Fe77Co4Zr9B10合金在晶化初期,α-Mn型晶化物的析出导致矫顽力(Hc)恶化;在943K退火后,Hc的下降与α-Mn型晶化物的消失和α-Fe相体积分数的增加有关。     

基于DSC技术的铜基非晶合金变温动力学的研究

基于大块非晶合金优异性能以及广阔的工程应用前景．采用DSC技术对大块铜基非晶合金Cu50Zr43A17进行了变温晶化动力学研究研究结果表明：晶化转变温度点与加热速度的立方根成正比．随着加热速度的增加．终了温度与晶化开始温度之差越大．晶化发生的温度区间越宽。     

Cu-Zr-Ag-Al非晶合金晶化过程的动力学效应

采用铜模吸铸法制备了直径3 mm的Cu_(40)Zr_(44)Ag_8Al_8大块非晶合金(BMGs),并分别利用X射线衍射仪(XRD)和同步示差扫描量热仪(DSC)对其晶化过程中显微结构的演变及其晶化动力学进行研究。结果显示,该BMGs在晶化过程中依次从非晶基体中析出Al_3Zr和Cu_10Zr_7相。采用Kissinger和Ozawa方法计算的非晶样品第一晶化峰的晶化激活能分别为315.69和312.65 k J/mol,该非晶合金具有很强的热稳定性。此外,该非晶合金晶化过程具有很强的动力学效应,特征温度对升温速率的依赖性遵循Lasocka方程,但其晶化机理函数却无明显的动力学效应,与加热速率无关。采用GM模型对30 K/min加热速率下的DSC实验数据进行拟合,发现其拟合参数由λi=5.2,n=3.4变为λi=2.5,n=4,说明该非晶合金的晶化行为遵循形核率随时间增加而不断增加的初晶型晶化规律。     

Structural transformation and rheological processes in bulk metallic glass Zr41Ti14Cu12.5 Ni10Be22.5

The temperature dependence of strain and strain rate of the Zr41Ti14Cu12.5Ni10Be22.5 (Vitl) bulk metallic glass (BMG) under constant heating condition was derived from the static extension method with a dynamic thermal mechanical analyzer (DMA). A few strain rate peaks, which corresponds to the glass transition and multistep crystallization in the differential scanning calorimeter (DSC) examination, were observed in the curves of the relation between strain rate and temperature. The onset of viscous flow and the end of glass transition are interrelated, the first and second strain rate peaks correspond with the first and second crystallization transition processes, respectively.The influence of stress on strain and strain rate was researched. It is found that the rheological behaviour of BMG Vitl changes from elasticity to anelasticity, finally to the Newtonian viscous flow along with increasing temperature.     

Dynamic mechanical behavior of a Zr-based bulk metallic glass during glass transition and crystallization

The dynamic mechanical behaviors of the Zr41Ti14Cu12.5Ni8Be22.5Fe2 bulk metallic glass (BMG) during continuous heating at a constant rate were investigated. The glass transition and crystallization of the Zr-based BMG were thus characterized by the measurements of storage modulus E and internal friction Q-1. It was found that the variations of these dynamic mechanical quantifies with temperature were interre-lated and were well in agreement with the DSC trace obtained at the same heating rate. The origin of the first peak in the internal friction curve was closely related to the dynamic glass transition and subsequent primary crystallization. Moreover, it can be well described by a physical model, which can characterize atomic mobility and mechanical response of disordered condense materials. In comparison with the DSC trace, the relative position of the first internal friction peak of the BMG was found to be dependent on its thermal stability against crys-tallization.     

电脉冲孕育处理对Zr基块体非晶热稳定性及退火晶化的影响

通过先对Zr55Ni5Al10Cu30合金熔体施加脉冲电流处理,再利用非真空吸铸法制备出Zr55Ni5Al10Cu30块体非晶合金的方式,研究了电脉冲孕育处理对非晶热稳定性及退火晶化的影响。差分扫描量热(DSC)及X射线衍射(XRD)分析结果表明:经电脉冲孕育处理后Zr55Ni5Al10Cu30块体非晶合金的玻璃转变温度上升,晶化温度降低,过冷液相区变窄,同时玻璃转变激活能和晶化激活能有所减少。电脉冲孕育处理没有改变Zr55Ni5Al10Cu30块体非晶合金退火晶化相演变过程,但提高了非晶退火晶化率。电脉冲孕育处理对Zr55Ni5Al10Cu30块体非晶合金的晶化起到了促进作用。     

A Dy-based bulk metallic glass with high thermal stability and excellent magnetocaloric properties

A new heavy rare-earth-based Dy₃₆Ho₂₀Al₂₄Co₂₀ bulk metallic glass (BMG) with high thermal stability and excellent magnetocaloric properties has been prepared by a copper mold casting. Compared with the other known rare-earth-based BMGs, this BMG alloy possess higher glass transition temperature and crystallization temperature, larger effective activation energy for glass transition and crystallization. Under a modest magnetic field, this BMG alloy exhibits a comparable or even larger magnetocaloric effect than that the previously reported RE-based BMGs and crystalline compounds. The high thermal stability and the excellent magnetocaloric effect together with other merits of the BMGs make this BMG alloy suitable candidate for use as magnetic refrigerant in a temperature range below 50 K.     

Rheological and diffusion behaviours of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass around glass transition

1 Introduction Since the Au-Si metallic glass were firstly prepared by rapid cooling technique in 1960 by DUWEZ et al[1], the study of structure and property of metallic glass has received much attention. The atom transportation behaviors (rheological an…     

Toughness of as-cast and partially crystallized composites of a bulk metallic glass

The deformation and fracture response of a bulk metallic glass (BMG) post-annealing above the glass transition temperature is examined. The toughness of the glass-matrix composite exhibits a sharp transition beyond a critical volume fraction of crystallization to values as low as that of brittle silicate glass. Instrumented indentation tests supplemented by impact tests were used to study this ductile to brittle transition exhibited by the partially crystallized samples. Indentation on the anneal-embrittled specimens shows lateral cracks in addition to cracks along the corners. The applicability of the Poisson's ratio-toughness correlation with respect to partially crystallized samples is also investigated.     

Structure relaxation and crystallization of Al83Ni10Ce7 metallic glass

Structure relaxation and crystallization of Al₈₃Ni₁₀Ce₇ metallic glass were studied by different scanning calorimetry (DSC) and X-ray diffraction (XRD). According to the DSC scan, it is interesting to find that the second exothermic peak changes with pre-annealing temperatures (below glass transition temperature), suggesting a change in the amorphous structure upon relaxation. Continuous heating crystallization and isothermal crystallization exhibit different crystallization mechanism of the present alloy. fcc-Al and a metastable phase precipitate simultaneously in the first stage crystallization during continuous heating; however, only a metastable phase precipitates during isothermal annealing below glass transition temperature (T_g).     

氢对锆基块状非晶玻璃转变及晶化动力学的影响

利用非等温差热扫描量热分析方法及Kissinger方程，研究了H原子对Zr-Ti-Cu-Ni-Be块状非晶合金玻璃转变和晶化的激活能影响。结果表明，H能够提高玻璃转变温度和晶化温度，增加玻璃转变和晶化激活能；引起晶化不同阶段热焓减少；并且充入H能降低玻璃转变温度和晶化温度对加热速度的依赖程度。     

Zr_(47)Cu_(44)Al_9大块非晶合金的变温晶化行为

利用示差扫描量热仪(DSC)研究了Zr_(47) Cu_(44)Al_9大块非晶合金在连续升温过程中的的变温晶化行为.利用Kissinger方法计算其特征温度表观激活能,利用Doyle方法计算其局域激活能.结果表明,Zr_(47) Cu_(44)Al_9大块非晶合金具有良好的热稳定性.利用Kissinger方法计算得到的其玻璃转变激活能E_g为390.2kJ/mol、晶化激活能E_x为325.1kJ/mol、晶化峰值的激活能E_p为299.5kJ/mol.随着加热速率的提高,各特征温度值向高温端移动,其晶化峰值温度所对应的晶化体积分数减小.局域激活能随着非晶晶化体积分数的增加而逐渐减小.     

Gd60Co26Al14大块非晶合金的磁熵变

利用铜模吸铸法制备了Gd60Co26Al14非晶合金.采用示差扫描量热法(DSC),X射线衍射(XRD)和超导量子磁强计(SQUID)研究了其结构与磁热性能.XRD分析表明:铸态Gd60Co26Al14合金是完全的非晶结构;DSC测试显示Gd60Co26Al14合金在加热过程中在571 K发生玻璃化转变,并且出现了两个结晶温度,分别是602 K和642 K.SQUID测试结果表明:Gd60Co26Al14合金出现两个居里温度,分别是82 K和128 K;合金在外磁场5 T下82 K处的磁熵变达到7 J·(kg·K-1).