Investigation of SR method grown 0 0 1 directed KDP single crystal and its characterization by high-resolution X-ray diffractometry (HRXRD), laser damage threshold, dielectric, thermal analysis, optical and hardness studies

0 0 1 directed potassium dihydrogen orthophosphate (KDP) single crystal was grown by Sankaranarayanan–Ramasamy (SR) method. The 0 0 1 oriented seed crystals were mounted at the bottom of the platform and the size of the crystals were 10 mm diameter, 110 mm height. Two different growths were tried, in one the crystal diameter was the ampoule's inner diameter and in the other the crystal thickness was less than the ampoule diameter. In the first case only the top four pyramidal faces were existing whereas in the second case the top four pyramidal faces and four prismatic faces were existing through out the growth. The crystals were grown using same stoichiometric solution. The results of the two growths are discussed in this paper. The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), laser damage threshold, dielectric, thermal analysis, UV–vis spectroscopy and microhardness studies. The HRXRD analysis indicates that the crystalline perfection is excellent without having any very low angle internal structural grain boundaries. Laser damage threshold value has been determined using Nd:glass laser operating at 1054 nm. The damage threshold for the KDP crystal is greater than 4.55 GW cm⁻². The dielectric constant was higher and the dielectric loss was less in SR method grown crystal as against conventional method grown crystal. In thermal analysis, the starting of decomposition nature is similar in SR method grown KDP crystal and conventional method grown crystal. The SR method grown KDP has higher transmittance and higher hardness value compared to conventional method grown crystals.     

Influence of crystal—melt interface shape on self-seeding and single crystalline quality

The growth of Sb-based crystals (InSb, GaSb etc) was undertaken using resistive heater furnace by vertical directional solidification (VDS) technique. Crystal—melt interface shape during the growth was shown to convert from concave to convex along the crystal axis of the ingots. Many antimonide (Sb) crystals of 8 mm to 18 mm diameter were grown by optimized growth parameters. The forced convection and absence of conducting support to ampoule showed improvement in crystal quality of as grown ingots. Crystals showed preferred orientation and self-seeding. Results on interface shape and crystallinity of ingots were found to be in good agreement with the experiments.     

悬浮区域熔炼法制备REB6（LaB6、CeB6）单晶体及其表征

采用区域熔炼法成功制备出了高质量、高纯度、大尺寸的LaB6、CeB6单晶体。系统分析了制备过程中每个参数对晶体生长的影响,确定了晶体成长最佳工艺:(1)LaB6:转速为30r/min,生长速度为8～10mm/h,两次区熔;(2)CeB6:转速为30r/min,生长速度15～20mm/h,一次区熔。然后对晶体进行表征,主要方法有单晶衍射、断面扫描、拉曼衍射、摇摆曲线。由此可知悬浮区域熔炼法是制备高质量、高纯度、大尺寸REB6的最佳方法。     

High-Speed Incremental Forming Process: A Trade-Off Between Formability and Time Efficiency

Making use of “optimal experimental design,” the paper attempts to investigate individual and interactive effects of predictor parameters, namely tool size, pitch size, feed rate, spindle rotational speed, and blank thickness, on sheet formability in single point incremental forming (SPIF) process. For the sake of precision, a novel sensor system was developed and employed to detect crack as it initiates on SPIF test specimens. A novel benchmark for formability in SPIF was established by addressing normal strain along sheet thickness, maximum attainable forming angle, and the rate of variation in forming angle. The process was finally optimized in terms of maximum achievable formability and minimum processing time. Accordingly, high-speed forming (with forming speed of at least 5000 mm/min) was realized to be perfectly viable, whereas the sheet formability remains quite satisfactory (over 90% of the maximum value). The key role of high spindle speed (up to 3000 rpm) was also highlighted in this regard.     

Study and evaluation of abrasive water jet turning process performance on AA5083

In this study, the effect of processing parameters on surface roughness and macro surface characteristics was analyzed during the machining of Ø30 mm and 300 mm aluminum alloy AA5083 abrasive water jets. As the processing parameters (up to 10 mm min⁻¹, 15 mm min⁻¹, 20 mm min⁻¹ and 25 mm min⁻¹), abrasive flow rate (50 g min⁻¹, 150 g min⁻¹, 250 g min⁻¹ and 350 g min⁻¹), the lathe chuck rotational speed (25 min⁻¹, 50 min⁻¹, 75 min⁻¹ and 100 min⁻¹) and the nozzle approach distance (2 mm, 5 mm, 8 mm and 11 mm) were used in experiments. In experimental studies, the pump pressure (360 MPa) was used as a constant, in the form of an abrasive Garnet (100 mesh), and the nozzle diameter as 0.76 mm. According to the findings, the best results in terms of surface roughness were obtained as a result of turning speed and abrasive flow rate. When the macro surface characteristics were examined, it was found that the lathe chuck rotational speed increased, the rate of nozzle progression was low, the rate of abrasive flow was high and the nozzle approach distance was lower and the smoother surfaces were obtained.     

Bulk growth of gallium antimonide crystals by Bridgman method

Gallium antimonide crystals were grown by the vertical Bridgman technique. Effects of ampoule diameter and dopant impurities (Te, P and In) on growth were studied. Crystal stoichiometry and homogeneity were verified with electron-probe microanalysis. Impurity distribution was investigated by secondary ion mass spectrometry (SIMS) and electron probe micro analysis. Variations of etch pit density (EPD) along the length and the diameter were studied by image analysis method. Resistivity, mobility and carrier concentrations were measured along the length of the crystal.     

Homogeneous Si0.5Ge0.5 bulk crystal growth as substrates for strained Ge thin films by the traveling liquidus-zone method

Compositionally uniform Si_0.5Ge_0.5 bulk crystals were grown by the traveling liquidus-zone method which we developed for alloy crystal growth. Grown crystals were characterized as substrates for compressive-strained Ge thin films for high mobility p-channels of complementary metal oxide semiconductor transistors. Compositional uniformity was excellent and crystallinity was also excellent for 10 mm diameter crystals. However, crystallinity was degraded for 30 mm diameter crystals although compositional uniformity was excellent. Transmission electron microscope (TEM) observation showed high dislocation density at the interface between a Si seed and a grown crystal due to lattice mismatch. However, the dislocation density decreased as crystal growth proceeded. High quality 30 mm diameter crystals will be grown when the single crystal length is extended judging from TEM results. In this paper, we report on the growth and characterization of Si_0.5Ge_0.5 crystals as substrates for strained Ge thin films.     

Single- and double-pass FSW lap joining of AA5456 sheets with different thicknesses

Friction stir welding of AA5456 aluminium alloy with different thicknesses was investigated for single- and double-pass lap joint configurations. The influences of tool tilt angle in first and second passes, and rotational and welding speeds in second pass on metallurgical structure and joint strength were studied. The results indicated that tilt angle significantly influences material flow and imperfection formation, and accordingly controls the weld mechanical properties. The best results were achieved by tilt angle of 5° for single pass, and tilt angle, rotational speed and traverse speed of 5°, 250?rev?min^??1 an 50?mm?min^??1 respectively for double-pass. The characteristics of hooking and cold lap defects were used as criteria to recognise the influence of processing conditions on joint performance.     

The effect of tool rotational and traverse speed on friction stir weldability of AISI 430 ferritic stainless steels

In this study, the effects of tool rotational speed and traverse speed on welding of AISI 430 (X6Cr17, material number 1.4016) ferritic stainless steels by friction stir welding method are examined. Two specimens with dimension of 3 × 100 × 200 mm were joined in butt position. Tool rotational speeds were determined to be 560–1400 min⁻¹ and traverse speeds as 80–200 mm/min. During the studies, tool pressure force 3.5 kN and tool angle of 0° was kept constant. Hard metal carbide (WC-Co hard metal identified as K10) with equilateral triangle tip profile was used as the tool material. Determination of the tool advance speeds related to the tool rotation speeds giving the best-looking weld seals with acceptable values of mechanical properties was aimed.During welding of the specimens joined in butt position, the temperature change due to time and variation of the pressure force applied on welded specimens by the tool shoulder has been recorded. It has been observed that the best mechanical resistance values were obtained at tool rotational speed of 1120 min⁻¹ through five tool rotational speeds (560–1400). Also it has been observed that the best mechanical resistance values were obtained at traverse speed of 125 mm/min through five traverse speeds (80–200) with the constant tool pressure force of 3.5 kN and tool angle of 0°.     

Growth of potassium acid phthalate crystals by Sankaranarayanan–Ramasamy (SR) method and its optical characterization

Potassium acid phthalate crystal 140 mm long and 20 mm diameter has been grown from aqueous solution using modified SR method setup. The modifications were mainly focused for growth from aqueous solution. The ring heater assembly was fixed at the top of the ampoule for large evaporation. The grown crystals were characterized by optical transmission by UV–Vis spectrometer and optical birefringence studies. The UV–Visible spectrum shows that the KAP crystal has good optical transmission which shows the transmission of ∼ 100% for 0.5 mm thickness and 83% for 2 mm thickness. The birefringence value is found to be 0.179 and it is in the order of calcite crystals.     

6061铝合金无倾角搅拌摩擦焊工艺及性能

目的 为了适应空间曲面构件的搅拌摩擦焊,开展6061铝合金无倾角搅拌摩擦焊工艺及性能的研究。方法 采用无倾角搅拌摩擦焊用的搅拌头,对5 mm厚6061-T6铝合金板材进行试验,研究焊缝成形及接头力学性能,并分析接头组织特征。结果 零倾角搅拌摩擦焊接头从组织上可区分为5个不同区域：焊核区(WNZ)、热力影响区(TMAZ)、热影响区(HAZ)、轴肩影响区(SAZ)和母材(BM);随着搅拌头转速增加,焊缝宽度和焊核尺寸均先变大后变小;随焊接速度增加,焊缝宽度和焊核尺寸均逐渐变小;当焊接速度固定时,随搅拌头转速增加,接头拉伸强度先增加后减小;当搅拌头转速固定时,随焊接速度增加,接头拉伸强度逐渐增大。结论 采用无倾角搅拌摩擦焊接方法,能够实现对5 mm厚6061-T6铝合金板材的有效焊接。     

Production of tailor-welded blanks by vertical compensation friction stir welding technique

An attempt was made for the first time to fabricate tailor-welded blanks (TWBs) through the feasibility of selective alloying in the solid state of vertical compensation friction stir welding (VCFSW) technique. The results revealed that the production of TWBs by VCFSW technique had higher homogeneity without any defects when compared to the production of TWBs by conventional FSW process at constant tool rotational speed 2000?rpm, traverse speed 20?mm?min^?1 and an inclination angle 2.5°. The maximum mechanical properties of the fabricated TWBs were obtained when the width of compensation strip 1.5?mm was used. The fracture surface of TWB at the width of compensation strip 1.5?mm showed ductile fracture mode.     

工艺参数对AA2524回填式搅拌摩擦点焊接头成形及力学性能的影响

目的 改善2 mm厚AA2524回填式搅拌摩擦点焊（RFSSW）接头的成形和力学性能。方法 采用不同扎入深度和不同转速进行焊接,焊后对接头的孔洞大小、套筒退出线上的裂纹长度和拉剪强度进行对比,获得扎入深度和转速对接头成形和拉剪强度的影响规律。结果 扎入深度为2.6 mm时,接头孔洞较小,断裂载荷较高。随着转速的增加,接头孔洞逐渐减小,套筒退出线的裂纹减少,拉剪强度逐渐升高。扎入深度2.6 mm,焊接时间6 s,转速为2600 r/min时,获得了无孔洞和无退出线裂纹的接头,断裂载荷最大,为9.4 kN。结论 合适的扎深和转速匹配,可以获得成形良好,高断裂载荷的接头。     

电子束修复IC10高温合金熔覆层组织分析

目的研究沉积速度对IC10熔覆层显微组织、显微硬度的影响以及界面的结合特征。方法采用真空电子束填丝焊对IC10镍基单晶高温合金进行修复试验,采用XJP-2C型倒置光学显微镜观察熔覆层OM图像,能谱仪(EDS)测定各区域元素分布情况,401MVD型数显显微硬度计测量接头显微硬度。结果在熔覆层上部出现等轴晶区和转向枝晶区,当沉积速度为220 mm/min时,熔覆层底部中心线左侧为取向一致的柱状晶,右侧为等轴晶;当沉积速度增加至300 mm/min时,底部等轴晶全部由柱状晶所取代。当沉积速度为220 mm/min时,熔覆层与基体区的显微硬度值基本相同;当沉积速度增加到300 mm/min时,熔覆层的显微硬度值最小。结论随着沉积速度的增加,熔覆层横截面底部柱状晶数量明显增多,而等轴晶数量明显减少,最后全部由柱状晶取代,同时熔覆层的显微硬度值呈递减趋势。此外,在沉积速度为260 mm/min时,结合面实现了良好的冶金结合。     

工艺参数对基于3D打印支撑模具板料双点渐进成形性能的影响

目的 提高基于3D打印支撑模具的板料双点渐进成形的成形性能,获得更好的成形参数。方法 选择工具头直径、加工步长、进给速度3个工艺参数为因素,设计单因素实验,加工支撑模具半径为45 mm的球冠,获得成形破裂角度,得到成形性能较好的工艺参数范围,确定成形性能较高的双点渐进成形方案。结果 通过实验数据对比并综合表面质量、加工时间及成形精度等因素考虑,最佳工艺参数工具头直径为 10 mm（实验选择8, 10, 12 mm）,垂直层进给量为0.5 mm（实验选择0.2, 0.5, 1 mm）,加工进给速度为 400 mm/min（实验选择300~500 mm/min）。结论 一定区域内工具头半径越小,垂直层进给量越大,工具头进给速度越大,板料成形性能越好。     

Growth and properties of CuInS2 single crystals

CuInS₂ single crystals 14–16 mm in diameter and up to 40 mm in length were grown by the traveling solvent method. The crystals were found to ben-type, with a conductivity of 0.1–10 S/cm, carrier concentration of 10¹⁶–10¹⁷ cm⁻³, and carrier mobility of 150–220 cm²/(V s). The anisotropic thermal expansion of the crystals was measured.     

Formation and mechanical properties of stationary shoulder friction stir welded 6005A-T6 aluminum alloy

6005A-T6 aluminum alloy is welded by stationary shoulder friction stir welding (SSFSW). At a constant rotational velocity of 2000 rpm, the effect of welding speed on mechanical properties of SSFSW joint are investigated in detail. Defect-free joint with gloss surface and small flash is attained and no cracks appear at the bending angle of 180°. Compared with traditional friction stir welding (FSW), width of rotational shoulder affected zone is relatively small because of the smaller diameter of rotational shoulder. Increasing welding speed is benefit for reducing the width of softening region and the softening degree. The fracture position of welding joint locates in thermo-mechanically affected zone and the fracture surface morphology presents the typical ductile fracture. The maximum tensile strength of joint at the welding speed of 400 mm/min reaches 82% of base metal (BM).     

Corrosion study and quantitative measurement of crystallite size of high strength aluminum hybrid composite developed via friction stir processing

This present study is centered on the corrosion behaviors and structural integrity of high strength aluminum-alloy 7075-T651 hybridized with carbonaceous coconut shell ash (CSA) and α+β titanium alloy powder in ratio of 50 : 50, fabricated during friction stir processing (FSP). The study examined the base metal – AA7075-T651 as well as the friction stir processed AA7075-T651 as control experiments. The Processing parameters used were plunge depth of 0.3 mm, travel speed of 20 mm/min, the tilt angle of 3° and rotational speed of 1500 min⁻¹. The corrosion characteristics were examined with the Potentiodynamic Polarization method in 3.5 % NaCl medium while crystalline phases were studied with x-ray diffraction (XRD). Results show that fabricated aluminum hybrid composite (AHC) AA7075-T651/coconut shell ash (CSA)/titanium-alloy has the highest percentage of inhibition performance efficiency (IPE) of 84.81 % resulting to 0.76938 mm/year corrosion rate and 356.51 Ω polarization resistance, whereas inhibition performance efficiency (IPE) for friction stir processed (FSPed) AA7075-T651 was 63.99 % while the base metal – AA7075-T651 was taken as the reference point. It was also revealed that the hybridized coconut shell ash (CSA)/titanium-alloy powder on AA7075-T651 enhanced the structural integrity, producing 38.5 nm crystallite size over friction stir processing (FSP) AA7075-T651 with 41.2 nm and the base metal with 48.7 nm crystallite size.     

Formation of a Tribologically Transformed Surface (TTS) on AISI 1045 Steel by Friction Stir Processing

Superficial nanostructuration by friction stir processing (FSP) experiments has been carried out on samples of AISI 45 steel. Sixteen tests were carried out, with a traverse speed in the range of 10–70 mm/min and 900–1800 N for the normal force at a constant rotational speed of 2000 rpm, in order to determine the optimal conditions for the process applied to this material and to test its feasibility. The results obtained have shown that FSP in this range of parameters leads to the formation of a stirred layer of small grains (30 times smaller than the initial grains) with high hardness (approximately doubled). When the load is higher than 1500 N and the traverse speed is superior to 50 mm/min, a white layer (WL) with very high hardness can be produced. It has also been determined that the increase of the stirred layers’ thickness is almost linked to the increase of the normal force.     

Effect of friction stir welding process parameters on Mg-AZ31B/Al-AA6061 joints

In the present study, dissimilar alloys such as Mg-AZ31B and Al-AA6061 were joined by friction stir welding using different rotational (560, 710, 860 and 1010?rpm) and transverse speeds (16 and 25?mm/min). Metallographic studies (by optical, scanning electron microscope, SEM, and energy dispersive spectrometer, EDS) revealed that the speed parameters mainly influenced the microstructure growth mechanism, which further affects the mechanical properties and corrosion behavior. The combined dynamic action of rotational to transverse speed recrystallized and plasticized the material and produced an alternative lamellar shear band of Al and Mg in the stir zone (SZ). Peak temperature and high rotational speed formed an oxide on the top region and also caused liquation and intermetallic (IMCs) formation. Tensile strength and hardness increased as per the Hall–Petch (fine grains) effect. Higher impact energy was found at moderate rotational and low transverse speeds due to the presence of more soft Al patches. Tensile fractographs showed a river-like pattern, which indicated the brittle nature of the joints. High rotational and high transverse speed illustrated higher tensile strength, while better corrosion resistance was observed in high rotational and low transverse speed.