Evaluation of defect density, microstructure, residual stress, elastic modulus, hardness and strength of laser-deposited AISI 4340 steel

The series of books represents a thorough treatment of ultra-high temperature materials with melting (sublimation or decomposition) points around or over 2500 °C. In the third volume are included physical (structural, thermal, electromagnetic, optical, mechanical, nuclear) and chemical (more than 1100 binary, ternary and multi-component systems, including those used for materials design, data on solid-state diffusion, wettability, interaction with chemicals, gases and aqueous solutions) properties of titanium monocarbide TiC1–x, vanadium monocarbide VC1–x and related 2D-molecular (graphene-like) carbide MXenes, discovered and developed only in the last decade. TiC1–x and VC1–x are also widely applied in the general technological and engineering practice in a wide range of temperatures as parts of highly hard materials (alloys) and special steels. This book will be of interest to researchers, engineers, postgraduate, graduate and undergraduate students alike. For the named materials, readers/users are provided with the full qualitative and quantitative assessment, which is based on the latest updates in the field of fundamental physics, chemistry, nanotechnology, materials science, design and engineering.

http://link.springer.com/content/pdf/10.1007/978-94-024-2039-5.pdf

Ultra-High Temperature Materials III: Refractory Carbides II (Ti and V Carbides)

Amorphous solids such as glass are ubiquitous in our daily life and have found broad applications ranging from window glass and solar cells to telecommunications and transformer cores. However, due to the lack of long-range order, the three-dimensional (3D) atomic structure of amorphous solids have thus far defied any direct experimental determination. Here, using a multi-component metallic glass as a model, we advance atomic electron tomography to determine its 3D atomic positions and chemical species with a precision of 21 picometer. We quantify the short-range order (SRO) and medium-range order (MRO) of the 3D atomic arrangement. We find that although the 3D atomic packing of the SRO is geometrically disordered, some SROs connect with each other to form crystal-like networks and give rise to MROs, which exhibit translational but no orientational order. We identify four crystal-like MROs - face-centred cubic, hexagonal close-packed, body-centered cubic and simple cubic - coexisting in the sample, which significantly deviate from the ideal crystal structures. We quantify the size, shape, volume, and structural distortion of these MROs with unprecedented detail. Looking forward, we anticipate this experiment will open the door to determining the 3D atomic coordinates of various amorphous solids, whose impact on non-crystalline solids may be comparable to the first 3D crystal structure solved by x-ray crystallography over a century ago.

Determining the three-dimensional atomic structure of an amorphous solid

Precipitate evolution and strengthening behavior during aging process in a 2.5 GPa grade maraging steel

The microstructure, precipitates and mechanical properties of Nb-V-Ti microalloyed ultra-high strength steel under different tempering temperatures are investigated. With the increasing tempering temperature, the width of martensitic laths gradually increased with reduced dislocations within them, and the volume fraction of retained austenite first increased and then decreased. Furthermore, the Charpy impact toughness, reduction of area and elongation are enhanced at the sacrifice of the strength. Four kinds of precipitates are identified at different tempering temperatures, namely M 3 C, M 2 C, M 23 C 6 and M 7 C 3 . M 3 C precipitated when tempering at 200–400 °C, and it was replaced partially by M 2 C when the temperature is elevated to 500 °C, at which M 23 C 6 also precipitated. For a higher temperature, above 600 °C, M 3 C disappeared, and some M 2 C transformed into M 7 C 3 . The other two types of MC precipitates are found to be the stable phases existing over different tempering temperatures. The correlation between the mechanical properties and microstructure was established, and the precipitation mechanisms of carbides at the different tempering temperatures are explained.

Carbide precipitation in Nb-V-Ti microalloyed ultra-high strength steel during tempering

The influence of tempering temperature on the reversed austenite formation and tensile properties are investigated in Fe-13%Cr-4%Ni-Mo low carbon martensite stainless steel in the temperature range of 550-950 degrees C. It is found that at the temperatures below 680 degrees C, the reversed austenite formation occurs by diffusion. Amount of the reversed austenite is determined I:IN the tempering temperature and the holding time. The segregation of Ni is the main reason for the stability of the reversed austenite. When the temperatures are above 680 degrees C, the reversed austenite formation proceeds by diffusionless. The reversed austenite will transform back to martensite after cooled to room temperature. The tensile properties are most strongly influenced by the amount of the reversed austenite obtained at room temperature. The excellent combination of good strength and ductility is at 610 degrees C. (C) 2011 Elsevier B.V. All rights reserved.

The influence of tempering temperature on the reversed austenite formation and tensile properties in Fe–13%Cr–4%Ni–Mo low carbon martensite stainless steels

Fe–Cr–Ni–Mo high-strength steels with four different V contents (0%, 0.03%, 0.08% and 0.14%) were prepared in this paper and carbides evolution was investigated by means of three-dimensional atom probe (3DAP) and transmission electron microscopy (TEM). The results indicated that there appeared M C, M 2 C and M 6 C types of carbides after addition of V in the steels while it was M 23 C 6 in 0.0%V steel ( M is any combination of Cr, Mo, Mn, Fe or V), and the size of carbides decreased gradually with improving V content. The mechanical properties significantly depended on the content of V. The strength and elongation increased gradually with increase in the V content, meanwhile the impact toughness decreased gradually. The excellent combination of mechanical properties can be obtained in the steel with about 0.03%—V content.

Yuanyuan Song

Papers

The influence of tempering temperature on the reversed austenite formation and tensile properties in Fe–13%Cr–4%Ni–Mo low carbon martensite stainless steels

Carbides and mechanical properties in a Fe–Cr–Ni–Mo high-strength steel with different V contents

Precipitates and alloying elements distribution in near α titanium alloy Ti65

Microstructure and Mechanical Properties of 06Cr13Ni4Mo Steel Treated by Quenching–Tempering–Partitioning Process

Anomalous Phase Transformation from Martensite to Austenite in Fe-13%Cr-4%Ni-Mo Martensitic Stainless Steel