Characterization of dispersed intermetallic phases in rapidly quenched Al-Ti-Ce alloys

The microstructures of Al-3Ti-lCe (wt pct) and Al-5Ti-5Ce alloys melt-spun under controlled He atmosphere have been characterized using analytical electron microscopy. The rapidly solidified microstructures comprise uniform, fine-scale dispersions of intermetallic phase in an aluminum matrix, and particular attention has been given to identification of the dispersed phases. In the Al-3Ti-lCe alloy, the dispersed particles are polycrystalline with a complex twinned substructure and a diamond cubic crystal structure(a _o =1.44 ±0.01 nm) and composition consistent with the ternary compound Al₂₀Ti₂Ce (Al₁₈Cr₂Mg₃ structure type, space group Fd3m). In the Al-5Ti-5Ce alloy, there is, in addition to the dispersed ternary phase, a separate uniform array of fine-scale particles of the binary compound Al₁₁Ce₃. The majority of such particles have the body-centered orthorhombic structure of the low-temperature polymorph, α-Al₁₁Ce₃, but there is evidence to suggest that at least some particles developvia initial formation of the high-temperature body-centered tetragonal phase, β-Al₁₁Ce₃. The accumulated evidence suggests that both binary and ternary particles formed as primary phases directly from the melt during rapid solidification, leaving only small concentrations of solute in aluminum matrix solid solution. Both phases are observed to be resistant to coarsening for up to 240 hours at 400 °C. Formerly Research Fellow, Department of Materials Engineering, Monash University.     

Mossbauer Effect of Rapidly Quenched Al-Fe-V-Si-Mm Alloys

ＭｏｓｓｂａｕｅｒＥｆｆｅｃｔｏｆＲａｐｉｄｌｙＱｕｅｎｃｈｅｄＡｌ－Ｆｅ－Ｖ－Ｓｉ－ＭｍＡｌｌｏｙｓＷａｎｇＪｉａｎｑｉａｎｇ（王建强），ＣｈａｏＹｕｅｓｈｅｎｇ（晁月盛），ＺｅｎｇＭｅｉｇｕａｎｇ（曾梅光），ＺｈａｎｇＢａｏｊｉｎ（张宝金），Ｃｈ...     

Characterization of dispersed intermetallic

The microstructures of Al-3Ti-lCe (wt pct) and Al-5Ti-5Ce alloys melt-spun under controlled He atmosphere have been characterized using analytical electron microscopy. The rapidly so- lidified microstructures comprise uniform, fine-scale dispersions of intermetallic phase in an aluminum matrix, and particular attention has been given to identification of the dispersed phases. In the Al-3Ti-lCe alloy, the dispersed particles are polycrystalline with a complex twinned substructure and a diamond cubic crystal structure (α _o = 1.44 ± 0.01 nm) and composition consistent with the ternary compound Al₂₀Ti₂Ce (Al₁₈Cr₂Mg₃ structure type, space group Fd3m). In the Al-5Ti-5Ce alloy, there is, in addition to the dispersed ternary phase, a separate uniform array of fine-scale particles of the binary compound Al₁₁Ce₃. The majority of such particles have the body-centered orthorhombic structure of the low-temperature polymorph, α-Al₁₁Ce₃, but there is evidence to suggest that at least some particles developvia initial formation of the high-temperature body-centered tetragonal phase, β-Al₁₁Ce₃. The accumulated evidence sug- gests that both binary and ternary particles formed as primary phases directly from the melt during rapid solidification, leaving only small concentrations of solute in aluminum matrix solid solution. Both phases are observed to be resistant to coarsening for up to 240 hours at 400 °C. Formerly Research Fellow, Department of Materials Engineering,     

Structural State and Magnetic Properties of Nd2Fe14B-Type Rapidly Quenched Alloys

Using the X-ray, elastic neutron diffraction (END) and small angular neutron scattering (SANS) methods (Diffractometers D2 and D3 respectively), transmitting electronic microscopy (JEOL JEM-200CX) and magnetometry technique (vibrating sample magnetometer - VSM) the structure and magnetic properties of the rapidly quenched (RQ) alloys of the following compositions: A) Nd₁₄Fe₇₈B₈; B) Y₁₂Fe₈₂B₆; C) Nd_13.3Co_6.6Fe_72.6Ge_0.9B_6.6; D)Nd₉Fe₈₅B₆; E) Nd₉Fe₇₉B₁₂; F) Nd₉Fe₇₄Ti₄CB₁₂ have been studied. At some quenching conditions or after consequent heat treatments of these alloys the nanoscale state of the main 2–14–1 phase and α-Fe grains can be formed. Their size depends on the sample-preparation conditions and lies in the interval of 10–200 nm. Their influence on magnetic properties of alloys under study is discussed.     

Coarsening of dispersed intermetallic

Dendritic monocrystals of Al-4.5 wt pct Cu-2 wt pct Mn were directionally solidified at 0.20 m/h under a thermal gradient of 3 × 10³ K/m. Crystal pulling was stopped for various lengths of time prior to quenching the remaining liquid, thus making it possible to evaluate the transformation and coarsening kinetics of dispersed intermetallic phases, Al₆Mn and Al₂₀Cu₂Mn₃, as a function of temperature. Coarsening of Al₆Mn intermetallic particles surrounded by liquid (Type II) follows an average particle size relationship much closer than it does a relationship. This suggests that convection plays no important role in coarsening. For coarsening of Al₆Mn particles in a solid matrix (Type I) the relationship fits the experimental measurements reasonably well. Coarsening kinetics studies were extended to intermetallic particle sizes an order of magnitude finer than those occurring in directionally solidified alloy, in order to derive information required by an on-going project on the effect of intermetallic phase geometry on corrosion behavior. Jt was found that coarsening of Al₂₀Cu₂Mn₃ particles contained in a melt-spun ribbon follows a relationship, as predicted by Kirchner for grain-boundary diffusion-controlled ripening. Finally, coarsening of Al₆Mn particles surrounded by liquid indium film and contained in a plastically deformed matrix follows a relationship, as predicted by LSW theory for liquid diffusion-controlled ripening. Shortening the time required to obtain coarse intermetallic particles during a homogenization treatment is important in deep drawing. Formerly Graduate Student, Department of Metallurgy, University of Connecticut, Storrs, CT 06268     

Characterization of Continuous and Discontinuous Precipitation Phases in Pd-Rich Precious Metal Alloys

Aberration-corrected scanning transmission electron microscopy (AC-STEM), X-ray diffraction (XRD), electron backscatter diffraction, and electron probe microanalysis were applied to characterize continuous and discontinuous phase formation in precious metal alloys used in electrical contacts. The Pd-rich Paliney^® (^®Paliney is tradename of Deringer-Ney Inc., Bloomfield, CT) alloys contain Pd, Ag, Cu, Au, Pt (and Zn or Ni). With aging at 755 K (482 °C), nanometer-scale chemistry modulation was observed indicating spinodal decomposition. An ordered body-centered tetragonal (bct) structure was also observed with AC-STEM after the 755 K (482 °C) aging treatment and another phase, tentatively identified as β-Cu₃Pd₄Zn, was found by microscopy and XRD after prolonged holds at higher temperatures. During slow cooling or isothermal holds at high temperature [755 K to 973 K (482 °C to 700 °C)], a two-phase lamellar structure develops along grain boundaries by discontinuous precipitation. XRD and AC-STEM showed that the lamellar structure was comprised of Ag-rich and Cu-rich fcc phases (α ₁ and α ₂). The phases are discussed in relation to a pseudo-ternary diagram based on Ag-Cu-Pd, which provides a simplified representation of the discontinuous phase compositions in the multi-component alloy system.     

Development of Rapidly Quenched Soft Magnetic Materialsin China

Ｓｉｎｃｅｔｈｅｆｉｒｓｔａｍｏｒｐｈｏｕｓａｌｌｏｙｑｕｅｎｃｈｅｄｄｉ－ｒｅｃｔｌｙｆｒｏｍｍｅｌｔｗａｓｏｂｔａｉｎｅｄｂｙＤｕｗｅｚｅｔａｌ．ｉｎ１９６０［１］，ａｎｕｍｂｅｒｏｆｓｔａｂｌｅａｍｏｒｐｈｏｕｓｍｅｔａｌａｌｌｏｙｓｈａｖｅｂｅｅｎｐｒｅｐａｒｅｄａｎｄｅｘｔｅｎｓｉｖｅｌｙｉｎｖｅｓｔｉｇａｔｅｄ．Ｉｎ１９６６，ｔｈｅｆｉｒｓｔｉｒｏｎ－ｂａｓｅｄａｍｏｒｐｈｏｕｓａｌｌｏｙ，ＦｅＰＣ［２］，ｗｉｔｈｈｉｇｈｓａｔｕｒａｔｉｏｎｉｎｄｕｃｔｉｏｎｗａｓｄｉｓｃｏｖ－ｅｒ…     

快淬MmNi_(3.5)Co_(0.75)Mn_(0.55)Al_(0.2)合金的电化学性能

应用不同的快淬速度制取成分为ＭｍＮｉ３．５Ｃｏ０．７５Ｍｎ０．５５Ａｌ０．２的贮氢合金，并做了电化学充放电循环实验，比较了它们的电化学活化速度、放电容量、放电电压性能以及电化学循环稳定性。冷却速度越高，合金的电化学循环稳定性越好、放电电压平台越平坦，放电电压也稍高，但导致放电容量下降，初期活化困难。     

快速凝固偏晶合金的显微结构

采用雾化快速凝固技术制备了ＡｌＰｂ二元偏晶合金。对合金的显微结构分析结果表明，在快速凝固条件下，偏晶合金中的第二相形态从带条状转变为颗粒状。随冷速的增加，第二相在基体中的分布更趋均匀、细化；随冷速的降低和第二相含量的增加，第二相趋于分布于材料的表面。本文从凝固过程的凝固速度和固／液界面对第二相液滴的界面排斥对上述现象进行了解释。     

Factors Influencing the Return to Equilibrium of Quenched Beta Ti Alloys and of Massively Transformed TiAl-Based Alloys

The return to equilibrium of quenched beta Ti alloys and of massively transformed TiAl alloys are discussed in this article. In the case of Ti-15-3 (Ti-15V-3Sn-3Al-3Cr), it is shown that the addition of carbon leads to very significant refinement of the alpha, which precipitates during the aging of quenched samples and to the virtual elimination of grain boundary alpha. Correspondingly, there is no enrichment of oxygen at grain boundaries during aging of the C-containing alloy but significant enrichment in the C-free samples. The precipitation of alpha 2 in annealed massively transformed cast samples of TiAl alloys is shown to lead to very significant refinement of the as-cast structure and thus to a significant improvement in properties. The cast samples were either hot isostatically pressed (“hipped”) or annealed to precipitate the alpha, and it has been shown that the pressures used in “hipping” strongly influence the microstructure and properties. This unexpected result is shown to be due to the fact that the molar volume of alpha 2 is larger than that of gamma, and that cooling within the hot isostatic press or after annealing is rapid enough to retain the different proportions of alpha formed at the high temperature.     

非调质塑料模具钢中易切削相的分析

运用光学显微镜、扫描电镜、电子探针以及图像分析仪，分析了Ｓ、Ｓ－ＲＥ、Ｓ－Ｃａ－ＲＥ非调质塑料模具钢中易切削相的形貌、分布、组成及其对力学性能的影响。结果表明，经Ｃａ、ＲＥ处理的钢中，出现以ｍＣａＯ·ｎＡｌ２Ｏ３为核心的ＭｎＳ和ＣａＯ·Ａｌ２Ｏ３·ＴｉＮ·（Ｍｎ，Ｃａ）Ｓ·ＲＥ２Ｓ３组成的复合硫化物，多呈纺锤形，提高了钢的横向冲击韧性，另外采用适量的铝和微量的钛也有利于改善易切削相形态     

Characterization of a Rapidly Solidified Iron-Based Superalloy

Rapidly-solidified powders of an iron-based superalloy were characterized before and after consolidation by hot isostatic pressing. Powders made by inert gas atomization were compared to powders made by centrifugal atomization. Although many of the powder characteristics were similar, the microstructures were not. The inert gas atomized powder structure is cellular while the centrifugally atomized powder structure is dendritic. In general the finer powder particles have the finer micro-structure with the effect more noticeable in centrifugally atomized powders. After consolidation, the differences in microstructure are more dependent on the consolidation temperature and post-consolidation heat treatment than in the powder type or size. Higher consolidation temperatures and/or post-consolidation heat treatment will result in transformation of the as-solidified microstructures. The transformed microstructure and the mechanical properties can in some cases be related to the as-solidified structure. Heat treatment is needed to obtain mechanical properties equivalent to those of ingot metallurgy processed material.     

Structure-Property Relationships in Dual-Phase Cu-Al Alloys: Part I . Individual Phases

Dual-phase (α + martensite) microstructures were produced in binary Cu-Al alloys by quenching from the (α + β) phase field. A wide range of martensite volume fraction V_M was obtained, depending on alloy composition and quench temperatureT. Linear dependence onT of V_M was established. Predefined values for V_M can thus be achieved by adjustment ofT and alloy composition. Furthermore, the size, shape, and distribution of component phases can be varied in a predetermined fashion by means of controlled cooling from the β range. The properties of α and martensite were tracedvia microhardness measurements. The microhardness of martensite increases with quench temperature in spite of the accompanying decrease of its solute content. This is in accord with previous work and emphasizes the dominating role of martensite ordered structure on strength. Such strength depends only on quench temperature irrespective of overall alloy composition or morphology. The α microhardness is not affected by alloy composition or quench temperature. The martensitic phase can be hardened by means of short time tempering due to order hardening or solute clustering effects. Depending on quench temperature, optimum use of such temper hardening can be achieved. Moreover, cold working of dual-phase structures followed by annealing at temperatures around 300 °C achieves substantial strengthening of both α and martensite. The strengthening of α is a consequence of anneal hardening. Although such high strength levels are accompanied by reduction of the ductility (as measured by thickness reduction achieved by cold rolling), the heat treatment schedule can be optimalized to achieve high strength while restoring ductility.