Effect of Mischmetal on Oxidation Resistance of 55Al－Zn Alloy Hot Dip Coating

ＥｆｆｅｃｔｏｆＭｉｓｃｈｍｅｔａｌｏｎＯｘｉｄａｔｉｏｎＲｅｓｉｓｔａｎｃｅｏｆ５５Ａｌ－ＺｎＡｌｌｏｙＨｏｔＤｉｐＣｏａｔｉｎｇＺｅｎｇｐｅｎｇ；（曾鹏）（ＧｕａｎｇｄｏｎｇＭｅｃｈａｎｉｃａｌＣｏｌｌｅｇｅ，Ｇｕａｎｇｚｈｏｕ５１０６４３，Ｃｈ...     

Improvement on Hot Workability of γ-TiAl Base Alloy

γ- Ti Al base alloys are potential aerospaceengine materials because of their low density andhigh performance at elevated temperature[1] .Thebrittleness at room temperature is still chiefroadblock to their application. During the lastdecade,the efforts to improve the ductility ofγ-Ti Al base alloy have been made[2 ] .A fine fullylamellar (FFL ) microstructure was founded to havegood ambient ductility and fracture toughness.Itcan be obtained through thermal mechanicalprocessing (TMP) and …     

A Study on Hot Tearing Susceptibility of Al–Cu,Al–Mg,and Al–Zn alloys

The present investigation deals with the hot tearing susceptibility of A206, A518, and A713 alloys. The hot tearing tests of the mentioned alloys were conducted at three different pouring temperatures using sand mold casting. Metallic cores designed to facilitate constrained radial contraction of the aforementioned alloys were used for casting. Macroscopic cracks were found in all the samples except in A518 alloy. It was observed that pouring temperatural and grain size have significant effect on crack susceptibility. Among the investigated alloys, A713 was found to be extremely prone to hot tearing. The microstructure characteristics of the alloys were studied using optical and scanning electron microscopy. Relationships between the pouring temperature, grain size and crack lengths of the alloys were also established.     

Isothermal Solidification of an Al–Zn Alloy

In diffusion brazing, a brazing alloy layer thickness introduced into the gap between brazed parts is very small, which hinders the study of the isothermal solidification process. In this work, the isothermal solidification of an Al–Zn alloy is investigated at large volume and mass of the initial liquid that takes part in isothermal solidification. Zinc cylinders are caulked in the holes bored in aluminum cubes. The samples thus assembled are held at 500 ± 10°C for different times. The volume fraction of isothermal solidified crystals has been determined, and the growth rate of isothermal crystals is shown to decrease upon holding. The crystals formed during isothermal solidification width are up to 380 μm and length more than 1 mm. They are observed in the samples that are held more than 2 days. The zinc content in the isothermal solidified crystals corresponds to its mean content in the aluminum solid solution at 490–510°C, according to the Al–Zn phase diagram. The composition of the former liquid that surrounded the crystals during isothermal solidification coincides with the equilibrium composition of the liquid in the Al–Zn system at a temperature of 490–510°C.     

Effect of Zr Content on the Microstructure and Corrosion Resistance of Al–Cu–Mn Alloy

Russian Journal of Non-Ferrous Metals - In order to improve the overall properties of cast Al–Cu–Mn alloy, the effect of Zr content on the microstructure and corrosion resistance of...     

Investigation on the Wear Properties of Primary Si Modified Al–20Si Alloy

In the present study, Al?C20Si alloy has been modified by Cu?C13P master alloy to obtain Al?C20Si?C0.1P alloy. The wear properties of Al?C20Si?C0.1P alloy have been investigated and compared with that of Al?C20Si alloy. The microstructure of Al?C20Si?C0.1P alloy consisted of primary and eutectic silicon distributed in the Al matrix. The size of primary Si is much smaller than that observed in Al?C20Si alloy. Wear tests have been conducted over a wide range of loads and sliding velocities. It has been observed that the wear rates of Al?C20Si?C0.1P alloy are lower than that of Al?C20Si alloy. The coefficient of friction is more or less constant in both the alloys but is low in Al?C20Si?C0.1P alloy. The better wear resistance of Al?C20Si?C0.1P alloy is discussed in the light of its modified microstructure evolved during solidification.     

Effect of Deep Cryogenic Treatment on Wear and Corrosion Resistance of an Al–Zn–Mg–Cu Alloy

Russian Journal of Non-Ferrous Metals - The 7075 aluminum alloy was subjected to deep cryogenic treatment (DCT) at –196°C with liquid nitrogen for different hours. The wear and corrosion...     

Processability and Structure Formation of the Al–Zn–Mg–Ca–Fe–Zr–Sc Alloy upon Hot Rolling and TIG Welding

Russian Journal of Non-Ferrous Metals - Technological regimes for producing wrought products (2 and 1 mm) from the Al–4.5%Zn–2.5%Mg–2.5%Ca–0.5%Fe–0.2%Zr–0.1%Sc...     

The Study of Hot Deformation Behavior of Mechanically Milled and Hot Extruded Al–BN Nanocomposite

Hot deformation behavior of mechanically milled and hot extruded Al–BN nanocomposite is investigated by hot compression test in the temperature range of 350–500 °C and strain rate of 0.001–1 s^?1. The plastic flow of the nanocomposite as a function of temperature and strain rate is described using a constitutive equation. Based on dynamic materials model, the processing map is developed at the strain of 0.7 representing stable and instable domains. The stable and instable domains in the processing map are verified by microstructural evaluation using transmission and scanning electron microscopes. The results show that the flow instability domains including micro voids and surface cracks have occurred in the range of: (1) T = 350–380 °C, \(\dot{\varepsilon }\) = 0.001–0.015 s^?1, (2) T = 370–430 °C, \(\dot{\varepsilon }\) = 0.1–1 s^?1, and (3) T = 460–500 °C, \(\dot{\varepsilon }\) = 0.001–0.03 s^?1. The safe and stable domains for hot deformation of nanocomposite have occurred in the range of: (1) T = 350–370 °C, \(\dot{\varepsilon }\) = 0.1–1 s^?1, (2) T = 390–450 °C, \(\dot{\varepsilon }\) = 0.003–0.05 s^?1, and (3) T = 440–500 °C, \(\dot{\varepsilon }\) = 0.1–1 s^?1. Finally, the investigation shows that the best processing parameters for this new nanocomposite are within the temperature range of 390–450 °C and strain rate range of 0.003–0.05 s^?1.     

Effect of Yttrium on Microstructure and Hot Corrosion Preformance of Laser Clad Co-Based Alloy

The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re-sults show that the Y-containing cobalt base clad alloy has a finer microstructure and higher corrosion re-sistance to the salt mixture of 75% Na_2SO_4+25%NaCl at high temperature.The unique properties are ob-tained with addition of 0.875% Y for the formation of a continuous and compact oxide scale.The compactscale may act as a barrier for the inward diffusion of oxygen and sulphur and also for the outward diffusionof alloying elements.     

Influence of Strontium Addition on Microstructure and Mechanical Properties of an Al–10Si–5Cu Alloy

The microstructure and mechanical properties of Al–10Si–5Cu cast alloys with micro-addition of alloying elements (V, Cr and Ni) were studied before and after strontium addition. Samples were examined using the X-Ray diffraction, the optical microscope, the scanning electron microscope and the energy dispersive spectrometer. The results indicated that the α-Al matrix, eutectic Si phase and Al₂Cu phase were the main constituent phases of Al–10Si–5Cu alloys before or after strontium addition. Strontium addition affected the refining of the α-Al grains and transforming the configuration of interdendritic phases. The un-modified alloy showed a brittle nature because of existing brittle and aggregated AlSiMnFe phases. Contributing to the alteration of microstructure in strontium modified alloy, the strength and elongation of the alloy were improved. In addition, the fracture mechanism and crack propagation process were investigated in both the alloys.     

Commencement of Ordering in Al–0.69Mg–0.31Si Alloy

Transactions of the Indian Institute of Metals - Early stages of ordering in dilute Al–0.69(at.%)Mg–0.31(at.%)Si alloy, aged at 373 K for 120 h and 7200 h and...     

Combined Effect of Calcium and Silicon on the Phase Composition and Structure of Al–10%Mg Alloy

Phase transformations in the Al–Ca–Mg–Si system in the region of aluminum–magnesium alloys are investigated using the Thermo-Calc program. The liquidus projection of the quaternary system is constructed with a Mg content of 10% and it is shown that phases Al4Ca, Mg₂Si, and Al₂CaSi₂ can crystallize (in addition to the aluminum solid solution (Al)) depending on the calcium and silicon concentrations. The crystallization character of quaternary alloys is investigated with the help of a polythermal cross section calculated at concentrations of 10% Mg and 84% Al. Based on the analysis of phase transformations occurring in alloys of this section, the presence of the Al–Al₂CaSi₂–Mg₂Si quasi-ternary section in the Al–Ca–Mg–Si system was assumed. Three experimental alloys were considered from a quantitative analysis of the phase composition, notably, Al–10% Ca–10% Mg–2% Si, Al–4% Ca–10% Mg–2% Si, and Al–3% Ca–10% Mg–1% Si. Metallographic investigations and electron-probe microanalysis were performed using a TESCAN Vega 3 scanning electron microscope. Critical temperatures are determined using a DSC Setaram Setsys Evolution differential calorimeter. The experimental results agree well with the calculated data; in particular, a peak at t ~ 450°C is revealed for all alloys in curves of the nonequilibrium solidus and invariant eutectic reaction L → (Al) + Al₄Ca + Mg₂Si + Al₃Mg₂. It is established that the structure of the Al–3% Ca–10% Mg–1% Si alloy is closest to the eutectic alloy. It is no worse that the AMg10 alloy in regards to density and corrosion resistance and even surpasses it in hardness, which allows us to consider this alloy as the basis for the development of a new cast material: “natural composites.”     

Effect of Melting Process on the Microstructure and Mechanical Properties of Fe–7 wt% Al Alloy

This article presents the effect of melting process on chemical composition, microstructure and mechanical properties of Fe–7 wt% Al alloy. The alloy ingot was prepared by air induction melting (AIM), air induction melting with flux cover (AIMFC) and vacuum induction melting (VIM) and cast into 50 mm diameter split cast iron mould. These cast ingots were hot-forged and hot-rolled at 1,373 K to 2 mm thick sheet. Hot-rolled alloys were characterized with respect to chemical composition, microstructure and mechanical properties. Ingots produced by AIM, AIMFC and VIM were free from gas porosity, however AIM ingots exhibited higher concentration of hydrogen as compared to AIMFC and VIM. The recovery of aluminium as well as reduction of oxygen during AIM is very poor as compared to AIMFC and VIM. AIMFC ingots exhibit low level of sulphur as compared to AIM and VIM ingots. The alloys produced by AIMFC and VIM exhibited superior tensile ductility compared to the alloys produced by AIM. The tensile properties of alloys produced by AIMFC are comparable to the alloys produced by VIM.     

Microstructure and Properties of Hot Rolled Ti23Al17Nb Alloy Sheets

 Microstructure and tensile properties of the Ti-23Al-17Nb alloy sheets rolling at （α2＋B2＋O）phase field with the various heat treatments were studied. Before rolling the microstructure of B2 phase particles embedded in O phase continuity matrix is acquired. The B2 phases deform more greatly and recrystallize more easily than α2/ O phases during the same rolling step. The (α2＋B2) two-phase equiaxed microstructure is obtain by solution treatment at (α2＋B2) phase field. The B2 phases become the continuity matrix by recrystallization and growing up of B2 grains and the anisotropy caused by rolling disappears. The microstructure obtained by solution treatment has more excellent tensile properties than the microstructure gained by subsequent aging treatment at (O＋B2) phase field because the O phases precipitate as the block structure during aging and the B2 matrix continuity is broken down.     

Effects of Al content on porous Fe–Al alloys

Abstract

Porous Fe–Al alloys with the nominal composition ranging from Fe–20 wt-%Al to Fe–60 wt-%Al have been fabricated by Fe and Al elemental powder reactive synthesis. The effects of the Al content on the pore properties of resultant porous Fe–Al alloys were systematically studied. It has been found that the volume expansion, the open porosity and the permeability can be manipulated by varying the Al content and that their maximum values are reached at Fe–45 wt-%Al. Their mechanical properties suggest that they are strong enough for the filtration applications.     

Influence of a Silicon Additive on Resistivity and Hardness of the Al–1% Fe–0.3% Zr Alloy

Isothermal sections of the diagram of the Al–Fe–Si–Zr alloy at temperatures of 450 and 600°C, as well as polythermal sections at concentrations of silicon up to 2 wt % and zirconium up to 1 wt %, are analyzed using computational methods with the help of Thermo-Calc software. It is shown that the favorable phase composition consisting of the aluminum solid solution (Al), the Al₈Fe₂Si phase, and Zr (which completely enters the composition of the solid solution (Al) during the formation of the cast billet) can be attained in equilibrium conditions at silicon concentrations of 0.27–0.47 wt %. To implement the above-listed structural components in nonequilibrium conditions and ensure that Zr enters the (Al) composition, experimental ingots were fabricated at an elevated cooling rate (higher than 10 K/s). A metallographic analysis of the cast structure of experimental samples revealed the desired structure with contents of 0.25 wt % Si and 0.3 wt % Zr in the alloy. The microstructure of the Al–1% Fe–0.3% Zr–0.5% Si alloy also contains the eutectic (Al) + Al₈Fe₂Si; however, the Al₈Fe₂Si phase partially transforms into Al₃Fe. The structure of the alloy with 0.25 wt % Si in the annealing state at 600°C contains fragmented particles of the degenerate eutectic (Al) + Al₈Fe₂Si along the boundaries of dendritic cells. It is established that the Si: Fe = 1: 2 ratio in the alloy positively affects its mechanical properties, especially hardness, without substantially lowering the specific conductivity during annealing, which is explained by the formation of the particles of the Al₈Fe₂Si phase of the compact morphology in the structure. Moreover, silicon accelerates the decay of the solid solution by zirconium, which is evidenced by the experimental plots of the dependence of hardness and resistivity on the annealing step. The best complex of properties was shown by the Al–1% Fe–0.3% Zr–0.25% Si alloy in the annealing stage at 450°C with the help of the optimization function at specified values of hardness and resistivity.     

Microstructure and Properties of Fe–Cr–B–Al Alloy After Heat Treatment

By means of optical microscope, scanning electron microscope, X-ray diffraction, energy dispersive spectrometer, Rockwell and Vickers hardness tester, and wear tester, the microstructure and properties of Fe–10Cr–1B–4Al alloy quenched in different temperature has been studied. The results show that the microstructure of as-cast Fe–10Cr–1B–4Al are composed of pearlite, ferrite and the eutectic borocarbide which shows a network distribution along grain boundaries. The eutectic borocarbides are composed of M₇(C, B)₃, M₂(B, C) and M₂₃(C, B)₆. As the quenching temperature increases, the network structure of eutectic borocarbide breaks, but the type of eutectic borocarbide has no obvious change, and the matrix structure changes gradually from ferrite to pearlite. As the quenching temperature increases, the macro-hardness and the matrix micro-hardness of Fe–10Cr–1B–4Al alloy increases gradually. The macro-hardness and matrix micro-hardness of alloy reach the highest value of 45.7 HRC and 388.1 HV, respectively when the quenching temperature is 1150 °C. The hardness of alloy decreases slightly when the quenching temperature is too high. While quenching at 1150 °C, the alloy has the highest wear resistance and good comprehensive properties.     

Effect of Rare Earth on Superplasticity of Zn—5Al Eutectic Alloy

Zｎ Ａｌａｌｌｏｙｉｓｏｎｅｏｆａｌｌｏｙｍａｔｅｒｉａｌｓｗｉｄｅ ｌｙｕｓｅｄｉｎｉｎｄｕｓｔｒｙ .Ｚｎ 5Ａｌｅｕｔｅｃｔｉｃａｌｌｏｙｉｓｎｏｔｏｎｌｙｅｘｔｅｎｓｉｖｅｌｙｕｓｅｄａｓｄｉｅ ｃａｓｔｉｎｇａｌｌｏｙ ,ｈｏｔｐｌａｔｉｎｇａｎｄｓｐｒａｙｉｎｇａｌｌｏｙ ,ｂｕｔｏｂｔａｉｎｓｒｅｃｏｇｎｉｔｉｏｎｉｎｓｕｐｅｒｐｌａｓｔｉｃｓｈａｐｉｎｇａｎｄｓｕｐｅｒ ｐｌａｓｔｉｃｔｈｅｏｒｅｔｉｃａｌｒｅｓｅａｒｃｈｅｓｏｗｉｎｇｔｏｉｔｓｅｘ ｔｒａｏｒｄｉｎａｒｙｓｕｐｅｒｐｌａ…