Innovative processing routes in manufacturing of metal matrix composite materials

Metal matrix composites (MMCs) belong to a group of modern materials owing to their excellent technological, mechanical, and physical properties such as excellent wear and corrosion resistance, high electrical and thermal conductivity, improved strength and hardness. Final properties of MMCs are affected equally by all steps of its manufacturing process. It is shown that by using adequate process parameters to obtain starting materials (reaching the specific size, shape, and reactivity) the control of volume fraction and distribution of reinforcements within the matrix can be achieved. For this purpose, mechanical alloying has been appointed as a good approach. MMCs can be produced using powder metallurgy, ingot metallurgy, and additive manufacturing techniques. Combining high-energy ball milling with these techniques enables the design of an innovative processing route for MMCs manufacturing. Mechanochemical process (achieved using high-energy ball milling) was employed in three manufacturing procedures: hot pressing, compocasting, and laser melting/sintering for obtaining of the suitable powder. These production routes for MMCs manufacturing were the subject of this work. The aim of MMCs design is to establish an optimal combination of production techniques merged into the cost-effective fabrication route for obtaining MMCs with required properties.

Microstructure, Properties and Corrosion Resistance of As-Cast Al-12Si-1.0Mn-0.6Mg-xSc Alloys

Al-12Si-1.0Mn-0.6Mg-xSc (x = 0, 0.1, 0.2, and 0.3) alloys for electronic packaging were prepared by ingot metallurgy, and the microstructure, mechanical properties, thermo-physical properties and corrosion resistance were compared. A fine and dispersed Al3Sc phase is observed and the acicular β-Fe phase transforms into a Chinese character or massive α-Fe phase in the alloys with Sc addition. When the Sc content increases from 0 to 0.3%, the secondary dendritic arm spacing and the size of the eutectic Si reduce from 17.9 μm and 5.3 μm to 12.8 μm and 3.1 μm, respectively. Simultaneously, the morphology of eutectic Si changes from a rough long rod to an ellipsoid. The thermal expansion coefficient and thermal conductivity of the alloys reduce slightly with increasing the Sc content. The flexural strength of 291.9 MPa is obtained for the Al-12Si-1.0Mn-0.6Mg-0.3Sc, an increment of 20.4% as compared with the Sc-free alloy. Furthermore, the corrosion resistance of the alloys is improved by the minor Sc addition.

An Additively Manufactured Titanium Alloy in the Focus of Metallography

Additive manufacturing processes allow the production of geometrically complex lightweight structures with specific material properties. However, by contrast with ingot metallurgy methods, the manufacture of components using this process also brings about some challenges. In the field of microstructural characterization, where mostly very fine structures are analyzed, it is thus indispensable to optimize the classic sample preparation process and to furthermore implement additional preparation steps. This work focuses on the metallography of additively manufactured Ti‑6Al‑4V components produced in a selective laser melting process. It offers a guideline for the metallographic preparation along the process chain of additive manufacturing from the metal powder characterization to the macro- and microstructural analysis of the laser melted sample. Apart from developing preparation parameters, selected etching methods were examined with regard to their practicality.

Effect of process parameters on the phase transformation kinetics in copper-based alloys and composites

Copper-based alloys and composites, owing to their convenient properties, are being considered essential materials in various industries. Since copper possesses an ability to develop high corrosion resistance, putting it in the domain of a desirable material in the manufacturing of valves, pipes, and also systems that carry industrial gases and aqueous fluids. Its usage is also invaluable for cables and electrical wires. This review paper describes diversity in copper alloy processing techniques (powder and ingot metallurgy) which are alongside the phase transformation kinetics interpreted and explained in detail. Furthermore, the focus is put on the copper alloys, as well as the kinetics present in these systems, with the application being highlighted. Correlation between physical properties and phase transformation kinetics in copper alloys is made. It is shown that if certain alloying elements are to be added, different properties could be improved. The effect of phase precipitation on phase transformation kinetics of copper alloys is shown by studying the Cu–15Ni–8Sn alloy.

Influence of Forging and Heat Treatment on the Microstructure and Mechanical Properties of a Heavily Alloyed Ingot-Metallurgy Nickel-Based Superalloy

The newly designed ingot-metallurgy nickel-based superalloy SDZhS-15 intended for disc applications at operating temperatures up to 800–850 °C was subjected to homogenization annealing and canned forging at subsolvus temperatures, followed by solid solution treatment and ageing. Mostly a fine-grained recrystallized microstructure was obtained in the forgings. It was revealed that post-forging solid solution treatment at T > (Ts-50), where Ts is the γ′ solvus temperature, led to a significant γ grain growth, which in turn led to a decrease in strength and ductility of the superalloy. The solution treatment at (Ts-60)–(Ts-50) allowed to save fine γ grains (dγ = 10–20 μm) and to provide the formation of secondary γ′ precipitates with a size of around 0.1 μm. In the forged and heat-treated conditions, the superalloy demonstrated superior mechanical properties, particularly excellent creep resistance at 650–850 °C in the stress range of 400–1200 MPa. Microstructure examination of the creep-tested samples showed that a decrease in the creep resistance at 850 °C can be associated with enhanced diffusivity along γ grain and γ/γ′ interphase boundaries leading to formation of cracks along the boundaries. In spite of the heavy alloying, the topologically close-packed phases were not detected in the superalloy, including in the creep tested samples.

Synthesis and Evaluation of Biocompatibility of Cu-Al-Mn Shape Memory Alloy

In recent days, it is being found that shape memory alloys can be used in the medicinal field which helps to alleviate numerous disabilities in people. The Shape memory alloy are evaluated for biocompatibility in present work. The objective is to determine the biocompatibility of Cu-Al-Mn SMAs using the alloy of composition 10-14 weight. % Aluminium (Al), 5-9 weight% Manganese (Mn) and rest copper (Cu) through ingot metallurgy in a constrained atmosphere. The casted samples were homogenisation at 900°C for one and half hours and then rolled at 900°C. The rolled specimens were betatized for half an hour at 900°C followed by Step quenching in boiling water (100°C) and quenching in water at room temperature (30°C). They are cut to the dimension of 10 mm * 10mm * 1mm (breadth*length*height) and then effect of shape memory on obtained alloy was assessed. In continuation, in order to understand the biocompatibility of obtained alloy, the samples were analysed for antibacterial movement by turbido-metric process. The microorganisms utilized for biocompatibility are S.aureus and E.coli. The outcomes showed remarkable biocompatibility with the inference that it can be employed for invitrouses.