Stability of the Transition Zones in a Steel–Vanadium Alloy–Steel Sandwich after Thermomechanical Treatment

A priority in atomic power today is to develop a new material for fuel-rod casings in fast-neutron reactors. A radiation- and corrosion-resistant three-layer composite based on vanadium alloy and stainless steel has been developed. This composite potentially meets the operational requirements on fuel-rod casings in very challenging operating conditions (high temperatures, radiation, and aggressive media). The performance of this material depends on the quality of the joint between the three layers, which is determined by the preliminary deformation and heat treatment. In the present work, the influence of tempering on the chemical composition, structure, and strength of the joint between the vanadium alloy and steel in the sandwich obtained by hot pressing a three-layer pipe blank at 1100°C is studied. The components of the pipe are 20Kh13 (Russian standard) steel for the external layers and V–4Ti–4Cr vanadium alloy in the core. The structure and chemical composition at the interfaces is investigated by optical and electronic microscopy, with X-ray spectral analysis. The strength of the steel–alloy bond is assessed in compressive tests of an annular three-layer sample with a cut; acoustic-emission measurements are employed. Pressing is found to form a transition zone of thickness 10–15 μm between the vanadium alloy and the steel, which is characterized by diffusional interaction and has a variable chemical composition. This zone consists of a series of solid solutions, without the deposition of brittle phases, and consequently the junction between the layers is strong. No pores, peeling, or defect are observed at the steel–alloy junction. However, in compressive tests of semiannular three-layer samples with a cut after hot pressing, a crack is formed in the steel layer at the tip of the cut. Annealing at 800°C improves the transition zone by increasing the thickness corresponding to diffusional interaction. Consequently, in mechanical tests, the sandwich behaves as a monolithic material, without cracking or peeling between the steel and the vanadium alloy.     

Composition and Structure of the Diamond–Low Carbon Steel Transition Zone Obtained by Contact Heating in Vacuum at the Eutectic Temperature of Fe–C

Russian Journal of Non-Ferrous Metals - This study covers the structure, elemental, and phase composition of products formed in the contact interaction between diamond and low-carbon steel in...     

Cold Sintering of Fe–Ag and Fe–Cu Nanocomposites by Consolidation in the High-Pressure Gradient

Russian Journal of Non-Ferrous Metals - The results of fabricating dense Fe–Ag and Fe–Cu nanocomposites from mixtures of powders consolidated by high-pressure cold sintering and from...     

Structure of Fe–Nb–Cu–Si–B Nanocrystalline Alloy Strip Produced by Melt Spinning

Recently, amorphous and nanocrystalline magnetically soft iron alloys have been used to create protective materials that are effective in a broad range of magnetic and electromagnetic fields. These alloys are obtained in strip form by superfast quenching of a plane melt jet on a rapidly spinning cooled disk. In the production of amorphous strip, metal melted in a high-frequency inductor is supplied through a cut on the surface of the cooling disk. The surface layers of the congealing strip in contact with the cooled disk are cooled more rapidly than higher layers in no contact with the disk. As a result, residual compressive stress may be formed on the contact side of the strip, while tensile stress may be formed on the free side. This may lead to anisotropic structure and properties over the strip thickness. In the present work, the structure is investigated by transmission microscopy (planar geometry and cross-sectional geometry) over the thickness of AMAG-200 Fe–Nb–Cu–Si–B alloy strip obtained by spinning. A relation is established between AMAG-200 Fe–Nb–Cu–Si–B alloy strip produced in controlled crystallization and the structure of the amorphous strip obtained by superfast quenching of melt at rates up to 10⁶ K/s. That explains the structural anisotropy over the strip thickness. Heat treatment at 530°C forms excellent magnetic characteristics and decreases the work of destruction on account of the formation of optimal amorphous–nanocrystalline structure in terms of the bulk content and size of the crystallites. A scanning electron microscope is used to study the destruction of strip associated with the structure formed in the strip on superfast quenching from melt and after heat treatment at 530°C. In the state supplied, the surface fracture of the strip on sudden decrease in grain size is ductile; after heat treatment, it is consistently brittle.     

Microstructural characterisation of Ti–Nb–(Fe–Cr) alloys obtained by powder metallurgy

Abstract

β alloys based on the Ti–Nb alloy system are of growing interest to the biomaterial community. The addition of small amounts of Fe and Cr further increases β-phase stability, improving the properties of Ti–Nb alloy. However, PM materials sintered from elemental powders are inhomogeneous due to restricted solid state diffusion and mechanical alloying provides a route to enhance mixing and elemental diffusion. The microstructural characteristics and bend strength of Ti–Nb–(Fe–Cr) alloys obtained from elemental powder mixture and mechanical alloyed powders are compared. Mechanical alloying gives more homogeneous compositions and particle morphology, characterised by rounded, significantly enlarged particles. In the sintered samples α and β phase are observed. The α phase appears at the grain boundaries and in lamellae growing inward from the edge, and is depleted in Nb. The β phase is enriched with Nb, Fe and Cr. The addition of Fe and Cr significantly increases the mechanical properties of Ti–Nb alloys, providing increased ductility.     

Chemical Composition and Structure of Interfacial Boundaries in Cr3C2–Ti Powder Hard Alloys after Explosive Compaction and Subsequent Heating

Russian Journal of Non-Ferrous Metals - The results of studying the fine structure, chemical composition, and phase composition of boundaries between components of the Cr3C2–Ti hard alloy...     

Effect of Processing Parameters on the Structure and Properties of Powder Fe–Al Intermetallic Compounds Obtained by Sintering and Impulse Hot Pressing

Powder Metallurgy and Metal Ceramics - The paper examines the effect of high-energy grinding and post-treatment conditions on the structure and physical and mechanical properties of iron aluminide...     

Nanostructured Gradient Material Based on the Cu–Cr–W Pseudoalloy Fabricated by High-Energy Ball Milling and Spark Plasma Sintering

Russian Journal of Non-Ferrous Metals - Nanostructured mechanical composites of immiscible metals Cu, Cr, and 5–70 wt % W; nanostructured consolidated materials based on them; and...     

Effect of Homogenization Treatment on Microstructure and Eutectic Precipitates in Ce-Containing 15Cr–22Ni–1Nb Austenitic Heat-Resistant Stainless Steel

The effects of homogenization temperature and time on microstructure and eutectic precipitates in Ce-containing heat-resistant stainless steel are studied. The increase in the homogenization temperature and time promotes the diffusion of alloying elements and the transition from dendrite structure to austenitic grain. Laves phase particles are fully dissolved after the homogenization of the ingots regardless of the cerium contents and homogenization temperature and time, except for the case of the homogenization at 1130 °C for 4 h. Honeycomb Laves phases gradually dissolve and become clusters of small blocky during homogenization treatment. The amount of eutectic NbC dissolved into the matrix is increased with the increase in the homogenization temperature and time. The solubility of niobium and carbon in austenite is increased with increasing the cerium content, which is beneficial to the dissolution of eutectic NbC. The distribution homogeneity of alloying elements in the austenitic matrix is increased with the increase in the cerium content. The homogenization temperature for reaching full diffusion of alloying elements into austenitic matrix is decreased with increasing the homogenization time. The decrease in the secondary dendrite arm spacing by cerium addition is favorable to the homogenization of alloying elements during homogenization treatment.     

Formation of a Tribofilm in the Surface Layer of Al–Ti–Cr–N–B Magnetron Coating on Boron Nitride During Turning of Hardened Steel

Powder Metallurgy and Metal Ceramics - The effect of cutting ShKh15 hardened steel on the element and phase composition of the surface layer of the coating deposited on the cBN-based tool is...     

Impact of in Situ Heat Treatment Effects during Laser-Based Powder Bed Fusion of 1.3343 High-Speed Steel with Preheating Temperatures up to 700 °C

For laser-based powder bed fusion (PBF-LB) of high carbon steels, preheated build platforms can reduce thermal stresses and crack formation inside the generated material. Furthermore, the heat distribution during PBF-LB is affected by laser energy input and heat transfer into the surrounding area. Depending on the preheating temperature and the thermal conditions during PBF-LB, thermal gradients and different thermal exposure times of the manufactured layers can lead to in situ heat treatment effects. As a result, gradients in microstructures and properties are observed in the manufactured material. The effects are investigated on AISI M2 high-speed steel (1.3343). Specimens are manufactured at platform preheating temperatures between 200 and 700 °C. Base plate and surface temperatures in the building layer are monitored by thermocouples and pyrometry. Local variations in the material microstructure and properties are determined and the effects of temperature distribution on microstructure and hardness are discussed.     

Mechanical Alloying with the Partial Amorphization of the Fe–Cr–Co–Ni–Mn Multicomponent Powder Mixture and Its Spark Plasma Sintering to Produce a Compact High-Entropy Material

Russian Journal of Non-Ferrous Metals - The results of studying the influence of mechanical alloying (MA) on the surface morphology, microstructure, and atomic–crystalline structure of...