Effects of thermo-mechanical processing and trace amount of carbon addition on tensile properties of Cu–2.5Fe–0.1P alloys

The effects of thermo-mechanical processing, including intermediate aging treatment and/or solution heat treatment, and a trace amount of carbon (C) addition were studied on tensile behavior of Cu–2.5Fe–0.1P alloys. In this study, Cu–2.5Fe–0.1P alloy sheets without and with a carbon content of 0.05 wt.% were cast and subsequently rolled and thermo-mechanically treated following various processing routes. The introduction of intermediate aging treatment between cold rolling improved the tensile strength of Cu–2.5Fe–0.1P alloys. Solution heat treatment prior to aging was proved to be detrimental on the tensile strength, probably due to recovery and recrystallization causing the complete loss of work hardening during previous cold rolling. The present study also suggested that two-step aging is more effective in improving the strength of Cu–2.5Fe–0.1P alloys than one-step aging. The effect of C addition on improving the tensile strength of Cu–2.5Fe–0.1P alloys was real but marginal, probably due to the limited solubility of C in Cu–2.5Fe matrix. The effects of intermediate heat treatments between cold-rolling processes on tensile properties of Cu–2.5Fe–0.1P specimens with and without C addition are discussed based on optical, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs, and SEM fractographs.     

Synthesis of Superconducting 2212 Phase in the Bi–Pb–Sr–La–Cu–O System

There have been no report about synthesis of the Bi-2212 compound in the Bi–r–La–Cu–O system. We have succeeded in synthesizing the Bi-2212 compound by partial substitution of Pb for Sr and/or Bi in the Bi–Sr–La–Cu–O system. Two samples of nearly the single 2212 phase have been obtained at a nominal composition of Bi_1.5Pb_0.5Sr_2.5La_0.5Cu₂O _z . Both of the samples crystallize in a psedotetragonal lattice, and their lattice parameters are a = 0.5476 nm and c = 3.085 nm or a = 0.5479 nm and c = 3.055 nm. They are both superconductors. The sample with longer lattice parameter c shows an onset of the resistivity drop and zero resistivity at higher temperatures of about 40 K and about 13 K, respectively. This sample also shows a diamagnetic signal starting at about 35 K with lowering temperature.     

Solidification microstructures and mechanical properties of high-vanadium Fe–C–V and Fe–C–V–Si alloys

Fe–C–V and Fe–C–V–Si alloys of various C, V and Si compositions were investigated in this work. It was found that the phases present in both of these alloy systems were alloyed ferrite, alloyed cementite, and VC_x carbides. Depending on the alloy composition the solidified microstructural constituents were granular pearlite-like, lamellar pearlite, or mixtures of alloyed ferrite + granular pearlite-like or granular pearlite-like + lamellar pearlite. In addition, it is shown that in Fe–C–V alloys the C/V ratio influences (a) the type of matrix, (b) the fraction of vanadium carbides, f_v and (c) the eutectic cell count, N_F. In Fe–C–V alloys, a relationship between the alloy content corresponding to the eutectic line was experimentally determined and can be described by where C_e and V_e are the carbon and vanadium composition of the eutectic. Moreover, in the Fe–C–V alloys (depending on the alloy chemistry), the primary VC_x carbides crystallize with non-faceted or non-faceted/faceted interfaces, while the eutectic morphology is non-faceted/non-faceted with regular fiber-like structures, or it possesses a dual morphology (non-faceted/non-faceted with regular fiber-like structures + non-faceted/faceted with complex regular structures). In the Fe–C–V–Si system, the primary VC_x carbides solidify with a non-faceted/faceted interface, while the eutectic is non-faceted/faceted with complex regular structures. In particular, spiral eutectic growth is observed when Si is present in the Fe–C–V alloys. In general, it is found that as the matrix constituent shifts from predominantly ferrite to lamellar pearlite, the hardness, yield and tensile strengths exhibit substantial increases at expenses of ductility. Moreover, Si additions lead to alloy strengthening by solid solution hardening of the ferrite phase and/or through a reduction in the eutectic fiber spacings with a decrease in the alloy ductility.     

Measurements of Vapor–Liquid Equilibria in the Systems NH3–H2O–NaOH and NH3–H2O–KOH at Temperatures of 303 and 318 K and Pressures 0.1 MPa<p<1.3 MPa

A static method has been used to obtain vapor–liquid equilibrium data for the systems ammonia (NH₃)–water (H₂O)–potassium hydroxide (KOH) and ammonia–water–sodium hydroxide (NaOH) at temperatures of 303 and 318 K and pressures from 0.1 to 1.3 MPa. The salt concentration in the liquid phase was chosen in the range from 2 to 60 mass% salt in water. In both systems NH₃–H₂O–NaOH and NH₃–H₂O–KOH, solid–liquid–vapor equilibria were observed. In the NH₃–H₂O–KOH system, liquid–liquid–vapor equilibrium was observed at 318 K and 1.1 MPa but at yet unknown concentrations of the liquid phases.     

Effect of mixture constituents on properties of slaked lime–metakaolin–sand mortars containing sodium hydroxide

In the present study, percentage of slaked lime (20–30%) in binder with metakaolin, water–binder ratio (0.8–1.0), sand–binder ratio (1–3) and sodium hydroxide (NaOH)–binder ratio (0.02–0.04) were factors varied to investigate properties of fresh or hardened mortars. Sodium hydroxide was used as a chemical activator in the slaked lime–metakaolin binders. Properties studied after 7 or 28 days of curing mortars at 40 ± 1 °C were consistency, compressive strength and water absorption. The physical, chemical, mineralogical and pozzolanic characteristics of materials used in study were determined. It was concluded that water–binder and sand–binder ratios are the most influential factors for consistency and water absorption of mortars. Compressive strength is influenced by all mixture constituents but NaOH–binder ratios less than 0.03 are recommended for use in mortars.     

Interaction of Cu–Al–Ni shape memory alloys particles with molten In and In + Sn matrices

Metal matrix composites for high-damping application were produced by embedding soft metallic matrices (pure In, In–10 wt.% Sn and In + Sn eutectic alloys) in powders of Cu–Al–Ni shape memory alloys (SMAs). During the composite production, the shape memory alloy particles interact with the molten matrices giving place to Cu dissolution from the shape memory alloy particles to the matrices, grain boundary penetration, and formation of intermetallic compounds. Adhesion, wetting and interfacial reaction are crucial for the final composites properties. Preliminary results on microstructural investigations performed applying optical and electron microscopy are presented in this contribution. The influence of thermal treatments on the microstructure of one composite is also discussed.     

Fatigue crack initiation in Ti–5Al–4Sn–2Zr–1Mo–0.7Nd–0.25Si high temperature titanium alloy

Ti–5Al–4Sn–2Zr–1Mo–0.7Nd–0.25Si alloy is a new high temperature titanium alloy for aeroengine use. In this paper, the fatigue crack initiation in this alloy was investigated. At applied maximum nominal stresses less than 500 MPa, most cracks initiate in the matrix away from the Nd-rich particles. Initiation of these cracks is related to the cracking of equiaxed α phase on the prior β grain boundaries. At high applied stresses, almost half of the cracks initiate in the matrix away form the Nd-rich particles and the other half initiate near Nd-rich particles. The probability that an Nd-rich particle initiates a fatigue crack decreases very rapidly as the particle size falls below 12 μm.     

Anisotropy of Young's modulus and tensile properties in cold rolled α′ martensite Ti–V–Sn alloys

Young's modulus and tensile properties of cold rolled Ti–8 mass% V and (Ti–8 mass% V)–4 mass% Sn alloy plates consisting of α′ martensite were investigated as a function of tensile axis orientation in this work. A single phase of α′ (hcp) martensite is obtained in Ti–8 mass% V and (Ti–8 mass% V)–4 mass% Sn alloys by quenching after solution treatment. By 86% cold rolling, acicular α′ martensite microstructures change into extremely refined dislocation cell-like structure with an average size of 60 nm, accompanied with the development of cold rolling texture in which the basal plane normal is tilted from the plate normal direction (ND) toward transverse direction (TD) at angles of ±49° for Ti–8% V alloy and ±46° for (Ti–8 mass% V)–4 mass% Sn alloy. No apparent anisotropy of Young's modulus (E) is observed for as-quenched Ti–8% V (E = 76–83 GPa) and (Ti–8% V)-4%Sn (E = 69–79 GPa). In contrast, Young's modulus increases with increasing angle from the rolling direction (RD) to TD for cold rolled Ti–8% V (E = 72–94 GPa) and (Ti–8% V)–4%Sn (E = 63–85 GPa). The observed anisotropy of Young's modulus can be reasonably explained in terms of the cold rolling α′ texture.0.2% proof stress and tensile strength are independent of tensile orientation for cold rolled Ti–8% V and (Ti–8% V)–4%Sn alloys. In contrast, larger elongation to fracture is obtained in specimens deviated by 30°, 45° and 60° from RD than by 0°, 75° and 90°. Scanning electron microscopy (SEM) fractographs reveal that quasi-cleavage-like fracture plane appears in 0° specimen of cold rolled Ti–8% V which shows brittle fracture and other specimens of cold rolled Ti–8% V and (Ti–8% V)–4%Sn alloys are fractured accompanied with necking and dimple formation. It is suggested from these results that brittle fracture is related to the activation of limited number of slip system and Sn addition leads to the activation of multiple slip systems.     

Effect of radio frequency and direct current modes of deposition on protective metallurgical hard silicon carbon nitride coatings by magnetron sputtering

Siliconcarbonitride (Si–C–N) coatings were deposited on silicon (100) by magnetron sputtering using radio frequency alternating current and direct current. The mechanical performance of the coatings in the two modes was compared through static indentation and scratch test in both microlevel and nanolevel. A structure–property correlation was attempted to establish mechanical behavior, microstructure and bond present in the film. Studies showed RF films to be mechanically tougher and having higher scratch resistance compared to the DC films.     

Interfaces Between Two or Three Coexisting Fluid Phases in the System Methane–Perfluoromethane: Calculations with the Born–Green–Yvon Equation

Wetting is studied for the binary mixture methane–perfluoromethane (CH₄–CF₄) with the Born–Green–Yvon (BGY) equation in the attractive mean field approximation (AMFA). The general phase behavior is consistent with the AMFA equation of state. Close to a three-phase equilibrium L₁L₂ V, perfect wetting of the interface L₁ V by the second liquid phase L₂ occurs. Liquid–vapor and liquid–liquid interfaces in the vincinity of the three-phase equilibrium are calculated with the BGY equation, and the surface tension is estimated from the density profiles. The results are compared to previous investigations of wetting in fluid systems, especially the theory of Cahn.