Effect of ultrasonic vibration on the grain refinement and SiC particle distribution in Zn-based composite filler metal

Refining the matrix microstructure of the composite is an effective method to avoid severe reinforcement particle pushing by the advancing solid–liquid interface during solidification. The effect of the ultrasonic vibration, which was injected into the melt at various stages of solidification, on the grain refinement and particle distribution in a Zn-based solidified composite filler metal was investigated. Perfect grain refinement was obtained with the application of continuous ultrasonic vibration. However, severe particle pushing by the sound radiation pressure was observed, resulting in serious particle segregation. Uniform distribution of SiC particles as well as grain refinement was obtained when proper intermittent ultrasonic treatment was applied.     

基于铸造铝合金过滤流动过程及过滤效率的模拟

采用水力学模拟实验对液态铝合金对滤流动过程进行了理论验证，分析了铝合金过渡流动过程中的流动规律，获得了液态金属过滤夹杂物的流动曲线。通过对实验液态铝合金的流动过程的分析进而研究与流动过程相关的过滤效率，最后给出了过滤效率的判别关系式。结果表明：过滤效率与雷诺数和过滤器的孔隙率密度相关。     

小管径超声波流量计的仿真与设计

针对时差法超声波流量计在小管径流量测量方面存在的问题,提出了一种内置反射装置的缩管径超声波流量计。采用FLUENT仿真软件,以管道内各声路上的K系数及均方根误差为评定标准,研究了反射片的形状、特征尺寸、反射片的间距及管道的缩进对管内流场特性的影响,设计了最佳管道模型,并计算出该模型在各流量点下的K系数。仿真结果表明所设计超声波流量计流场稳定,能够提高小管径测量的测量精度。     

AZ91HP镁合金变质精炼的实验研究

研究了AZ91HP镁合金在不同变质、精炼条件下铸件的组织和力学性能。结果表明：变质、精炼处理后，镁合金铸件晶粒得到细化，力学性能提高。其中CzCls变质结合氩气吹洗精炼效果最好，在此条件下，铸件T6状态力学性能达到了σ0.2=132．6MPa、σb=250．5MPa和δ—4．93％。进一步分析表明晶粒细化的机理为含C、A1化合物的异质形核作用。     

Application of ultrasonic treating to degassing of metal ingots

The relations between porosity in the ingot and the effecting factors such as the ultrasonic power and the time of ultrasonic vibration (UV) treating to melt were investigated. Moreover, the mechanism of the porosity formation and the prevention method was studied. The results indicate that the effect of degasification was better when the intensity of UV is above threshold value. On the contrary, the intensity of UV below the value resulted in the increase of the gas content in the ingot and the decrease of density. It could be confirmed that there is an appropriate time on degasification by UV treating. When treating time is over the time, the density of the ingot tended to decrease. By using UV to degas with constraint cooling in the bottom of the ingot, the value of porosity volume (PV) can be decreased below 0.1 cm³/100 g and the η_deg is near to 97%.     

硅系合金法提纯多晶硅的研究进展

硅系合金法近年来已成为冶金法提纯多晶硅的研究热点。大量研究表明,适合的硅系合金能使杂质在硅中的分凝系数大大降低。利用Si-Al合金,通过定向酸洗工艺所得到的多晶硅制成太阳电池其效率最高可达10.6%,在感应磁场下凝固能使Si有效分离,大大降低酸的用量。Si-Ga合金法制成的单晶硅锭,纯度可达5N,太阳能电池的效率也达到了15%,但成本较高。Si-Cu合金则具有容易分离的优点。同时介绍了其他硅系合金的研究进展。     

Effects of Zr and B on the structure and tensile properties of Al–20%Mg alloy

In current research, the effects of different Zr and B contents on the structure and tensile properties of Al–20%Mg alloy have been investigated by using Al–15Zr and Al–8B master alloys. Optical and scanning electron microscopy (SEM) were utilized to study the microstructures and fracture surfaces. Microstructural analysis of the cast alloy showed dendrites of primary α-phase within the eutectic matrix which consists of β-Al₃Mg₂ intermetallic and α-solid solution. After tensile testing, the optimum amounts for both Zr and B were found to be 0.5 wt.%. Ultimate tensile strength (UTS) value of the unrefined alloy increased from 168 MPa to 243 MPa and 236 MPa by adding 0.5% Zr and 0.5%B, respectively. The main mechanism for UTS enhancement was found to be due to the refinement of grains and also altering large dendrites of Al(α)-phase to finer structure. The study of fracture faces revealed that B/Zr addition changes the mode of fracture from brittle to rather ductile.     

Al-Li合金真空精炼与成分变化规律的研究

研究了Ａｌ－Ｌｉ合金真空除氢规律，并对比研究了真空除氢过程中化学成分变化规律，为Ａｌ－Ｌｉ合金的生产提供了重要参数，并为研究新一代高韧Ａｌ－Ｌｉ合金打下了基础。     

The effect of grain refining and oxide inclusion on the fluidity of Al–4.5Cu–0.6Mn and A356 alloys

The effect of grain refinement and oxide inclusion on the fluidity of Al alloy was investigated with a test casting with eight thin flow channels. Pouring in air increased the amount of oxide in the A356 melt. The fluidity compared between normal A356 melt and contaminated melt. The amount of oxide was evaluated qualitatively by ultrasonic treatment. The flow length varied linearly with the pouring temperature. By adding Ti and Al–5Ti–B, fluidity increased. The grain size decreased by adding grain refiner. The fluidity depended on the degree of grain refining. It was noticed that pouring in air increased the amount of oxides in the melt by ultrasonic treatment. The fluidity of contaminated melt was decreased comparing to the normal one especially in lower temperature.     

小径管超声导波检测有效检测距离研究

针对CFETR装置中真空管道的在役检测及维护方法,指出现有氦质谱检测技术的局限性。在此基础上,提出超声导波检测技术应用于真空管道检测,并且对应用中关键问题进行讨论。应用有限元法,分析了已确定结构及材料的管道检测的超声模态及波结构。在此基础上进行对检测距离进行数值模拟仿真,结果表明:对直径32 mm壁厚3 mm不锈钢管道,可单次检测出1 mm×4 mm×0.5 mm的表面裂纹,有较好的检测特性。最后,通过现场试验分析,得到检测信号反射系数与距离的关系(信噪比关系),对仿真进行了验证。     

Ultrasonic vibration assisted tungsten inert gas welding of dissimilar magnesium alloys

The effects of ultrasonic vibration assisted (UVA) treatment on the microstructures and mechanical properties of MB3/AZ31 dissimilar magnesium (Mg) alloy joints were studied by microstructural characterization, micro-hardness testing and tensile testing. Results indicate that the welding pores are eliminated and coarse ??-Mg grains of fusion zone are refined to 26 ??m, owing to the acoustic streaming effect and cavitation effect induced by the UVA treatment with an optimal ultrasonic power of 1.0 kW. In addition, Mg₁₇Al₁₂ precipitation phases are fine and uniformly distributed in the whole fusion zone of weldment. Micro-hardness of fusion zone of the Mg alloy joints increases to 53.5 HV after UVA process, and the maximum tensile strength with optimized UVA treatment increases to 263 MPa, which leads to fracture occurrence in the Mg alloy base plate. Eventually, it is experimentally demonstrated that robust MB3/AZ31 Mg alloy joints can be obtained by UVA process.     

Influence of repetitious-RRA treatment on the strength and SCC resistance of Al-Zn-Mg-Cu alloy

Influence of repetitious-retrogression and reaging (repetitious-RRA) treatment on the strength and SCC resistance of Al-Zn-Mg-Cu alloy was investigated by the slow strain rate technique (SSRT) and electrical conductivity test, using TEM, EDS and SEM. Additionally, the strength of alloy was characterized by Vickers hardness. The results show that within 3 times RRA treatments, SCC resistance increases with the increase of time, while maintaining strength as compared to RRA treatment, TEM observation along with EDS analysis indicates that within 3 times, matrix precipitates (MPs) in repetitious-RRA treatment are similar to those by RRA treatment and grain boundary precipitates (GBPs) become more discrete and coarser with the time. However, RRA treatment reaches 4 times, the SCC resistance gets worse because MPs are also coarse. Besides, the Cu content of GBPs increases with the time, inversely for Zn content, which is another reason for improving the SCC resistance.     

超声冲击对TC4钛合金组织和性能的影响

对TC4钛合金试样表面进行超声冲击强化处理。利用维氏显微硬度仪测量冲击后沿截面方向硬度分布,利用扫描电子显微镜观察经超声冲击后组织变化,利用X射线衍射仪测定冲击后表层晶粒尺寸和微观应变。试验结果表明,经超声冲击后,TC4钛合金的组织和力学性能发生了显著变化。随着冲击功率的增大．显微硬度显著提高,表层晶粒细化并产生一定数值的微观应变。     

Forming Process of Strong Anisotropic Material Based on the Hydrodynamic Deep Drawing with Radial Pressure

1.IntroductionA sketch of the conventional hydrodynamic deepdrawing(HDD)process is shown in Fig.1(a)[1~5].Ini-tially,the flange of the blank is in contact with the drawdie.When the punch is moved down,the liquid pres-sure in the die cavity increases and when the pressurereaches a certain magnitude,the flange is lifted from thedraw die and the liquid starts to flow out through thegap between the draw die and the flange[6~9].In FEMsimulation of the conventional HDD,it is very difficult todet…     

爆破振动频率对振动效应影响的试验研究

爆破振动效应取决于一次起爆的药量Q、距爆源的距离R、传播的介质以及振动频率F；该文总结了前人对爆破振动效应的研究成果，提出了考虑爆破振动频率的具体办法，发现在不同振动频率范围内，振动衰减规律不同。文章进行了工程实际验算，说明在主频率下，最大质点振动速度是真实的安全判据。     

活塞用近共晶铝硅合金熔体变质精炼复合处理技术的应用

铝合金熔体处理的主要目的是提高熔体的变质效果及纯净度,本文论述了当前国内广泛使用的几种铝合金熔体变质处理及净化处理技术,重点介绍了活塞用近共晶铝硅合金熔体P变质处理及氮气--氯气混合气体＋精炼剂复合净化处理技术在活塞铸造领域的应用。     

RH用机械真空泵抽气过程计算机仿真程序的开发

全干式机械真空泵正以其出色的节能环保效果越来越多的在冶金行业炼钢厂真空精炼工艺中得到应用, 因此开发一个能够与真空精炼过程相结合的机械真空泵抽气过程计算机仿真工具, 以方便系统的设计和研究, 显得尤为紧迫。本文详细描述了自主研发的真空循环脱气工艺 (RH) 用机械真空泵抽气过程计算机仿真程序的开发内容, 包括全干式机械真空泵方案的选择、钢液碳脱氧、氧脱碳或脱气反应产生的气体量模型、各级真空泵工作效率的计算模型、各级真空泵抽气能力确定的计算模型、机械真空泵的控制方法和控制参数、计算机仿真程序、各种中间过程参数和计算结果的输出、是否满足真空精炼过程的判定标准等, 完全能够满足全干式机械真空泵系统设计和研究的需要。     

Effect of grain refining and Sr-modification interactions on the impact toughness of Al–Si–Mg cast alloys

The present work investigates the effects of various types of grain refiners on the impact properties of Sr-modified A356.2 alloys in both the as-cast and heated-treated conditions. The results showed that the addition of Ti and B greatly improves the alloy toughness, but only when the alloy was in a fully modified state; moreover, the right type of master alloy and addition levels must be used. The highest values of the total absorbed energy recorded for T6-tempered alloys were obtained using Al–5%Ti–1%B and Al–10%Ti master alloys in addition to 0.04%Ti. A significant deterioration in the impact properties is observed due to the Sr–B interaction (in some cases). The improvements in toughness may be attributed to the change in Si particle morphology as well as to the dissolution and fragmentation of a number of the intermetallics formed during the T6 temper.     

超声温度对电机转子用Al-12%Si合金凝固组织及性能的影响

研究Al-12%Si合金在凝固期间受到不同功率超声作用时得到的组织结构, 对α (Al) 组织与Al+Si共晶相的微观形态进行了观察。实验测试结果表明:相对于未超声处理, 对各凝固阶段加入超声场作用之后都会明显减小凝固组织的数量与气孔尺寸。增加超声作用后可以使各阶段的Al-12%Si合金都在凝固期间形成更小的气孔率, 并且超声作用程度最明显的是液相阶段。受到超声作用的情况下, Si相发生了长宽比的显著减小, 对初生组织的形核与晶粒生长过程进行超声后, 得到了具有最小长宽比的Si相组织。加入超声处理后, 使Al-12%Si合金形成了具有更高硬度的初生α (Al) 相与共晶组织。与初生α (Al) 相比, 对合金液相进行超声时可以获得最大的硬度, 相对未超声处理组织增大了20.3%。经过超声处理后, Al-12%Si合金在压缩期间出现了墩粗变形, 具有明显的塑性变形特征, 其屈服强度发生了较大提升。