نشریه مهندسی متالورژی و مواد
سال سی و پنجم شماره 4 (پیاپی 36، زمستان 1403)

Heavy tungsten alloys are made by liquid phase sintering for application in protective weights, radiation shields, and anti-missiles. The change in each of the production parameters of these alloys affects the mechanical behavior of these alloys. The aim of this research is to assess the effect of annealing heat treatment cyclic on the bonding strength of tungsten particles with the matrix. Tungsten alloy with a chemical composition of 93.5W-5.4Ni-1.95Fe (in wt.%) is first compressed in a plastic mold (cold isostatic) following by liquid phase sintering at 1480 °C and two cycles of annealing heat treatment. In order to study the mechanical properties, tensile and hardness tests are used. Also, the microstructures and fracture surfaces (after tensile test) of the samples are examined using optical and scanning electron microscopes. The obtained results show that due to the thermal stresses during cooling and heating through the cyclic annealing heat treatment, the matrix phase is penetrated into the interface of tungsten particles which causes a decrease in the contiguity (from 0.44 to 0.31). Also, the cyclic annealing heat treatment reduces the impurities in the interface between tungsten particles and the matrix, resulting in an increase in strength (from 842 MPa to 960 MPa). Comparison of fracture surfaces of samples with annealing cyclic shows the change of brittle fracture mechanism to soft fracture. Keywords: Heavy tungsten alloys; Sintering; Heat treatment; Particles/matrix interface; Contiguity.

The rolling process is one of the common and widely used methods in manufacturing and forming various parts. The rolling process has a significant effect on the mechanical properties and microstructure of materials, which making it important in the manufacturing of products. 3D printing or additive manufacturing is a of the new method in producing parts that allows for the direct creation of parts from digital models. This process is based on creation parts layer by layer and can produce various parts quickly and with high precision. The unique features of additive manufacturing, such as design freedom, no need to dies and auxiliary equipment, and the ability to produce complex and integrated parts, have caught the attention of many industries such as aerospace, oil and gas, marine and automotive industries to use this method. In the other hand, problems such as microstructure defects, distortion, residual stress and anisotropy of mechanical properties are among the challenges in additive manufactured or 3D printed parts. Using the rolling process to modify 3D printed parts is one way to improve the microstructure and mechanical properties of materials. By combining the rolling process with additive manufacturing, hardness, strength, and elongation can be increased by homogenizing and refining grains of the structure. Also, this process can reduce distortion and residual stress in the additive manufactured parts.

Metal-phenolic networks are an emerging organic-inorganic hybrid network system that has been gradually developed in recent years through the coordination between metal ions and organic ligands containing phenolic groups, such as gallol or catechol. These networks exhibit exceptional multifunctional properties, specifically anti-inflammatory, antioxidant, and antibacterial functions. These materials greatly change the surface characteristics, resulting in improved performance in areas such as anti-corrosion, hydrophobicity, biocompatibility, and binding of specific molecule on various surfaces, including metals, oxides, polymers and biological materials. Furthermore, phenolic metal networks have attracted considerable attention in the field of infection prevention and advanced cancer therapies due to their easy synthesis process, remarkable biocompatibility, and outstanding antimicrobial properties facilitated by polyphenols and metal ions. The aim of this article is to provide an overview of the recent biomedical applications of phenolic metal networks in different structures, with a particular focus on their inherent characteristics, including novel antimicrobial and anticancer properties.

The precise prediction of forming limit curves (FLCs) is vital for improving the formability of steel sheets, significantly impacting industries like automotive and aerospace manufacturing. Despite its significance, current approaches for determining FLCs are complex and necessitate more reliable prediction models. This paper aims to introduce theoretical relationships for accurately predicting limit strains and constructing the FLC of steel sheets. By selecting four specific points on the FLC, the corresponding maximum and minimum limit strains were determined using analytical models based on finite element simulations of the M-K model. Two sets of parameters were considered: GTN damage model parameters (micro-scale) and Swift's equation variables (macro-scale). The seven studied parameters, including void volume fractions, adjustment parameter (q2), critical void volume fraction, nucleation void volume fraction, coefficient of strength, initial strain, and hardening exponent, were used as inputs for a central composite design of experiments. Each experiment represented a combination of the parameters and was simulated in four forming paths, providing coordinates for the FLC points. Interpolation of data from the finite element simulations led to the development of practical analytical functions for predicting the FLC of steel sheets. The functions' validity was demonstrated by computing multiple FLCs with randomly chosen parameter values and comparing them to FLCs obtained from the M-K model's simulations. The findings indicated that the formulated equations precisely determine the FLC of steel sheets. The predicted limit strain in the AISI304’s plane strain zone was 0.3647, exhibiting an error of 0.44% relative to the experimental value of 0.370.

In this research, the mechanical properties (microhardness and wear) of Al-8Si-3Cu-2Zn nanocomposites with 0, 2, and 5% by weight of tungsten disulfide nanoplates have been investigated. The studied nanocomposite was produced through mechanical grinding and hot pressing at a temperature of 510 degrees Celsius. The microstructures of powders before and after mechanical grinding and sintered samples were studied through electron microscopy (SEM). By examining the worn surfaces after the wear test by electron microscope, the cause of weight loss was investigated. The results show that by adding tungsten disulfide nanoplates up to 5% by weight, the microhardness of the samples increases more than twice and from 50 Vickers for Al-8Si-3Cu-2Zn to 101 Vickers for Al-8Si.-3Cu-2Zn nanocomposite reaches -5%WS2. According to the results of the wear tests, the wear rate for Al-8Si-3Cu-2Zn-5%WS2 will decrease by 32% %, compared to the Al-8Si-3Cu-2Zn alloy background. Therefore, Al-8Si-3Cu-2Zn-5%WS2 nanocomposite can be used as a self-lubricating nanocomposite with favorable wear properties.

In this research, the effects of solution annealing heat treatment on the hardness and microstructure characteristic of TM-321 Ni base superalloy are investigated. The temperature of annealing was chosen on the basis of thermodynamic analysis of Procast 2018 for TM-321 superalloy. At 1080°C the volume percent of γ/γ′ eutectic pool which was 9 Vol% in the as cast structure reduced to 1.7 vol% at 4h and it is stable till 6h. At 1180°C again it is considerably decreased to 1.2 vol%. At 1180°C and times more than 2h, numerous and fine clusters of γ′ precipitates formed. The formation of γ′ precipitates clusters will disrupt the creation of the proper distribution of γ′ precipitates. At 1180°C/2h, the lowest eutectic volume fraction (0.9%), the highest dissolution and reduction in the fraction and size of primary γ′ (21.5% and 84nm) are present, which has been chosen as the best conditions for solutionizing in this research.