Characteristics of the Dissipation of Energy at Hot Plastic Deformation of Near-Alpha Titanium Alloy

Change of mechanical properties of near-alpha titanium alloy is experimentally investigated at stretching in the conditions of variation of temperature and high-speed parameters of deformation. It is established that characteristics of mechanical properties, a structural state influence processes of dissipation of the spent energy. Studying of microstructure of samples before deformation by stretching allowed to install the main mechanisms of dissipative processes and to confirm a possibility of realization of superplasticity in the studied alloy

Chemical heterogeneity as a factor of improving the strength of steels manufactured by selective laser melting technology

The aim of this paper was to establish the causes of the heterogeneity of the chemical composition of the metal obtained by the LC technology. The powdered raw material was made from a monolithic alloy, which was fused by the SLM, the initial raw material was a laboratory melting metal of a low-carbon chromium-manganese-nickel composition based on iron. To determine the distribution pattern of alloying chemical elements in the resulting powder, electron-microscopic images of thin sections were combined with X-ray analysis data on the cross-sections of the powder particles. As a result, it was found that transition (Mn, Ni) and heavy (Mo) metals are uniformly distributed over the powder particle cross-sections, and the mass fraction of silicon (Si) is uneven: in the center of the particles, it is several times larger in some cases. The revealed feature in the distribution of silicon is supposedly due to the formation of various forms of SiO4 upon the cooling of the formed particles. The internal structure of the manufactured powder is represented by the martensitic structure of stack morphology. After laser fusion, etched thin sections revealed traces of segregation heterogeneity in the form of a grid with cells of ~ 200 μm

Shock-induced structures in copper

Shock loading of M3 copper within strain rate range of 5·10 6-5,7·10 6 s -1 reveals a nucleation of structural objects of 5-30 µm in diameter, which present the three dimensional frameworks composed from shear bands of 50-200 nm spacing. The structures are shown to be nucleated by means of interference of longitudinal and periphery release waves. Transition of the material into structure unstable state responsible for the shear banding happens when rate of change of the velocity variance at the mesoscale becomes higher than the rate of change of the mean particle velocity. The sites of nucleation of 3D-structures are speculated to be the staking faults generated under action of chaotic velocity pulsations relevant to dynamic deformation. The physical model for formation of 3D-structures takes into account the intersection of the partial dislocations and Lomer - Cottrell barriers

Study of characteristics of steel specimens after selective laser melting of powder materials MS1

At present, there is a great interest in the technologies of laser melting of metallic powders for the any shape items production. Over the past decade, the process of selective laser melting (SLM) of various powders based on alloys and steels was mastered. However, not so long ago, many studies were aimed at SLM stainless steels, including MS1 steel. The effect of laser radiation power, scanning speed, pitch, building direction on the microstructure and mechanical properties of the final product is studied. The influence of the parameters of the initial material, such as the chemical composition, the shape and size of the particles, and their distribution is indicated. Since the SLM process is sensitive to building parameters it is necessary to obtain more information about the mechanical and structural properties of standard samples in order to better understand the capabilities of this technology

Study of characteristics of steel specimens after selective laser melting of powder materials MS1

At present, there is a great interest in the technologies of laser melting of metallic powders for the any shape items production. Over the past decade, the process of selective laser melting (SLM) of various powders based on alloys and steels was mastered. However, not so long ago, many studies were aimed at SLM stainless steels, including MS1 steel. The effect of laser radiation power, scanning speed, pitch, building direction on the microstructure and mechanical properties of the final product is studied. The influence of the parameters of the initial material, such as the chemical composition, the shape and size of the particles, and their distribution is indicated. Since the SLM process is sensitive to building parameters it is necessary to obtain more information about the mechanical and structural properties of standard samples in order to better understand the capabilities of this technology