Design of a Co–Al–W–Ta Alloy Series with Varying γ′ Volume Fraction and Their Thermophysical Properties

The γ′ volume fraction is a key parameter in precipitation-strengthened Co- and Ni-base superalloys and mainly determines the alloys’ properties. However, systematic studies with varying γ′ volume fractions are rare and the influence on thermal expansion has not been studied in detail. Therefore, a series of six Ta-containing Co-based alloys was designed with compositions on a γ–γ′ tie-line, where the γ′ volume fraction changes systematically. During solidification, Laves (C14-type) and µ (D85-type) phases formed in alloys with high levels of W and Ta. Single-phase γ or two-phase γ/γ′ microstructures were obtained in four experimental alloys after heat treatment as designed, whereas secondary precipitates, such as χ (D019-type), Laves, and μ, existed in alloys containing high levels of γ′-forming elements. However, long-term heat treatments for 1000 hours revealed the formation of the χ phase also in the former χ-free alloys. The investigation of the thermal expansion behavior revealed a significant anomaly related to the dissolution of γ′, which can be used to determine the γ′ solvus temperature with high accuracy. Compared to thermodynamic calculations, differential scanning calorimetry (DSC) and thermal expansion analysis revealed a larger increase of the γ′ solvus temperatures and a lesser decline of the solidus temperatures when the alloy composition approached the composition of the pure γ′ phase.

The Basis for Reliability-Based Mechanical Properties of Structural Aluminium Alloys

Adequate knowledge of mechanical properties and their statistical description is the basis for performing reliable verification of design methods and design of structures in general. The probabilistic design approach implemented in Eurocodes requires statistical data on all variables used in the design procedure. Although aluminium was introduced in structural Eurocodes more than four decades ago (ENV), the statistical database of mechanical properties is still inadequate. To provide a reliable statistical background, data collection was performed concerning aluminium products mainly found in the European market, within the last 20 years regarding certificates from the aluminium industry and 30 years regarding data from the research community. The collected data include aluminium alloy series 1xxx, 5xxx, 6xxx, and 7xxx, mainly extruded, and relevant mechanical properties such as 0.2% proof strength, ultimate strength, Young’s modulus, and Poisson’s ratio. They were fit to distributions, and relevant fractiles were determined, along with an analysis of nominal to characteristic and design value ratios. Variation of ratios obtained shows that that the majority of nominal values are economical and reliable. However, certain adjustments to nominal values are required to achieve a uniform reliability level in terms of the choice of alloy and temper.

Entropy of Conduction Electrons from Transport Experiments

The entropy of conduction electrons was evaluated utilizing the thermodynamic definition of the Seebeck coefficient as a tool. This analysis was applied to two different kinds of scientific questions that can—if at all—be only partially addressed by other methods. These are the field-dependence of meta-magnetic phase transitions and the electronic structure in strongly disordered materials, such as alloys. We showed that the electronic entropy change in meta-magnetic transitions is not constant with the applied magnetic field, as is usually assumed. Furthermore, we traced the evolution of the electronic entropy with respect to the chemical composition of an alloy series. Insights about the strength and kind of interactions appearing in the exemplary materials can be identified in the experiments.

Tribology of Ti6Al4V: A review

The deleterious innate attribute of Ti6Al4V, the workhorse material among the alloy series of titanium is its incompetent tribo-behavior. Infinite surface modification techniques, viz., the accretion of adherent appendage layers, diffusion hardening, infusion of residual stresses, microstructural evolution, and phase transformations were attempted to enhance the wear resistance of the alloy. The need lies to establish a bridge between the indigenous material properties and the tribo-characteristics of Ti6Al4V so that the enforced improvement techniques can raise the barriers of its applicability. A critical review of the microstructural transitions, mechanisms governing tribo-behavior and the parametric conditions leading to material removal at dry sliding conditions of Ti6Al4V, falls under the scope of this manuscript. Hence, the prime focus of the approach is to impart a clear-cut perception of the minute variations in mechanical, metallurgical, and tribological characteristics of the alloy at interactive instances with distinct counter-body surfaces.

STRUKTUR MIKRO DAN SIFAT MEKANIS ALUMINIUM PADUAN SERI 6063 HASIL COR DARI CETAKAN LOGAM, PASIR RESIN FURAN DAN PASIR KOMOSSA

Material developments in Indonesia is already very advanced rapidly certainly need high level of violence but has a mass of light. Aluminum should be developed because it possesses a lightweight and available in the land of our country that is rich in agricultural products. As an alternative to strengthen aluminum alloy that is with Si and Mg, as well as the rapid cooling process when smelting. This study was conducted to observe the microstructure and mechanical properties of the raw material of aluminum alloy series 6063. Tests conducted with metal mold, furan resin sand mold, commossa sand mold, the cooling rate of each mold will affect the hardness of the material which can be seen microstructure with microstructural observations. The survey results revealed that the aluminum with a metal mold casting has a hardness of 54 HRB, furan resin sand has a hardness of 40 HRB, sand commossa has a hardness of 33 HRB. Metal mold has a shock force of 0,316 J/mm2, particularly a furan resin sand shock force of 0,265 J/mm2, commossa sand has a shock force of 0.206 J/mm2. Metal mold has a high hardness compared with furan resin sand rated second, while the sand was rated commossa end but increasingly harsh mean tenacity of a material value will increase. According to the test micro structure, the aluminum is brittle, the distance or the distribution of grain will be a meeting or a lot.

Formation of Al-Ti-B Phases for Grain Refinement of Al Alloys Produced by High Energy Ball Milling

In this experimental study, Al-Ti-B powders were ground in planetary ball mill to produce AlxTiyBz where x, y and z stands for the relative molar ratios of elements for the compilation of grain refiner compound. Powder size distribution, phase formation (XRD) and particle morphology was investigated by means of SEM and XRD. The fabrication of AlTiB phases and the grain refinement of Al alloys by adding this phase were aimed. For this purpose, the powders were fed to planetary ball mill to be milled at a speed of 600 rpm. The powders were also milled at different milling times as 30 min and 150 min either in metallic form or compound form of Al, Ti and B powders. The powders were dried after each milling to be characterized by SEM and XRD. The phases and morphology-elemental analysis were also conducted by XRD and SEM, respectively. Moreover, the powders were added to Al alloy castings avoiding the breaking through alloy series which are mainly used in aluminum industry. The Al alloy series were examined for grain refinement by Brinell hardness and optical microscopy for mechanical properties and grain formation as well as by SEM (EDS) for grain formation, morphology and elemental distribution analysis.

Iron as a Promising Alloying Element for the Cost Reduction of Titanium Alloys: A Review

This article focuses on the effect of iron (Fe) addition on the fabrication of Ti-alloys. Fe is a potential inexpensive element that can be added to Ti-alloys to reduce their cost. This metal can also be used to replace expensive β-stabilizing alloying elements, such as vanadium (V) and molybdenum (Mo), for Ti-alloys. Fe has also been utilized as a novel cost-effective alloying element to decrease Ti-alloy costs and to design other alloys, such as Ti metal 62S (Ti-6Al-1.7Fe-0.1Si) and Ti-Fe-O-N Ti-alloy. This technical perspective has been further applied to fabricate new Ti-alloys. For example, Ti8LC and Ti-5.5Al-1Fe with good mechanical features have been developed as novel Ti-alloys in China and Japan, respectively. Nowadays, vanadium (V) of Ti-6Al-4V alloy is completely replaced with Fe to produce Ti-Al-Fe alloy series. Three new alloys, namely, Ti-6Al-xFe, where x = 1, 2, and 3 wt%, are introduced to examine the effect of Fe addition on the microstructure and mechanical properties of Ti-alloys.