Papers by Keyword: Deformation Mechanism

Abstract: By means of solution treatment at various temperatures, creep properties measurement and microstructure observation, the effects of heat treatment on composition segregation and creep properties were investigated. Results show that the various segregation extents of the elements are displayed in the alloys solution treated at different temperatures, and the segregation extent of the elements is improved with the solution temperature elevated, which may obvious improve the creep resistance of the alloy. And no rafted structure of the γ phase is detected in the alloy during creep at medium temperature. The deformation features of the alloy during creep at medium temperature are that the slipping of dislocations is activated in the γ matrix channels, and dislocations shearing into the γ phase may be decomposed to form the configuration of partials + stacking faults, which may hinder the cross-slipping of the dislocations to improve the creep resistance of the alloy.

Abstract: According to the defects of powder metallurgy superalloy, especially the influence and damage of inclusions on properties of disk, the deviation between nondestructive testing and metallographic testing of inclusions in FGH96 alloy isothermal forging disk was investigated. Meanwhile, the types and deformation mechanism of inclusions were studied. The results showed that the buried depth tested by metallographic detection was less 67-180μm than nondestructive testing. The size of inclusions with metallographic detection was less about 18-50μm than nondestructive testing. The major types of inclusions in practical disk were Al₂O₃ and Al₂O₃-SiO₂, the inclusions run through several grains, no matter Al₂O₃ or Al₂O₃-SiO₂. The Al₂O₃ inclusion and matrix was purely mechanical bonding, but the Al₂O₃-SiO₂ had reaction zone. There was remarkable effect of extrusion process on crushing and dispersing Al₂O₃ inclusion, but which was unremarkable for Al₂O₃-SiO₂.

Abstract: Taken an open-pit landslide as an example, the cause of formation and the factors inducing the slope to failure are analyzed. According to deformation characteristic of the landslide, the deformation has been exacerbating with the deep mining in depth, and the deformation has close relationship with the rainfall. Rainwater infiltration, which soften the rock mass and induce the pore water pressure to increase, induce envoke landslides. Through analysis on the factors of landslides, the formation lithology(FL) and precipitation are main factors triggering generation and reactivation of landslides. Meanwhile, the deformation failure mechanism and instability mode of the landslide is obtained, which is the sliding and bending deformation model.

Abstract: Deformation mechanism of low-rigidity thin part caused by clamping force is studied in this paper. A coupled thermo-mechanical simulation process of aluminum alloy 6061 is developed using the finite element method with Abaqus. The results of simulation are verified by experimental measurements of cutting force and surface residual stress. Then using the model investigates the effect on residual stresses along the thickness of aluminum alloy 6061 load and unloadthe clamping forces. The deformation condition is also studied after removing fixing.

Abstract: Molecular dynamics simulations were carried out to investigate the plastic deformation mechanism of fcc crystalline materials using the conventional Lennard-Jones potential. An fcc structure with square cross-section was prepared, and a tensile load was applied in the longitudinal direction. A weak potential was assigned to a specific (111) plane to induce a slip on the specified plane. Accordingly, a slip was initiated in the weak plane following an elastic deformation. The step-by-step motion of the atoms on the slip plane was studied, and a detailed trajectory is presented. The slip then expanded to other planes, and plastic deformation progressed in the whole model. The weak plane was also set as (110) or (100) plane, where different deformation modes were observed: not only slip but also gradual distortion or brittle fracture occurred.

Abstract: Hot compressive deformation tests of burn resistant titanium alloy (Ti-35V-15Cr-Si-C) with initially as-cast and as-extruded microstructure were performed at deformation temperature between 900°C to 1200°C for as-cast and 900°C to 1150°C for as-extruded alloy, and strain rates between 10^-3 s^-1 to 1s^-1. The compressive true stress vs. true strain curves were measured, the deformation activation energy was calculated and the microstructures after deformation were studied. The results show that dynamic reversion is the primary soften mechanism of the burn resistant titanium alloy during hot deformation. At the higher strain rate ( =1s^-1), the ‘Necklace’ Dynamic Recrystallization will occur for as-cast alloy, and a Continuous Recrystallization will occur for as-extruded alloy. At the lower strain rates, both as-cast and as-extruded burn resistant titanium alloy display the continuous recrystallization. The extruded alloy presents larger dynamic recrystallization regions than that of the as-cast alloy.

Abstract: Under pressure and activity difference between drilling mud and poro fluid, the degredation of mudstone mechanic features will change with the saturation time. It reveals that the reduction of the mudstone strength parameter and the decrease of the elastic modulus are the results of hydration stress development after the mudstone hydration. This paper proposed that the damage of soft mudstone is caused by the hydration stress development. After introduced the internal damage variable in the linear constitutive equations of viscoelastic materials, the approximate equation about the changing rate of the internal damage variables and the changing rate of the hydration stress can be got.

Abstract: This paper investigates the evolution of the deformation mechanisms in a homogenized Mg-10Gd-2Y-0.5Zr alloy ingot compressed at 300-500 °C and 0.1-20 s^-1. It can be found that the basal slip and mechanical twinning are the major deformation mechanisms in the alloy compressed at 300 and 0.1-20 s^-1. Increasing the testing temperature to 350 °C, basal slip, non-basal slip and mechanical twinning control the plastic deformation of the alloy compressed at 0.1-20 s^-1. When the testing temperatures increase further to 400-500 °C, the mechanical twinning is replaced gradually by the local shear bands which are formed by dynamic recrystallization (DRX) grains (referred as transformation bands). The transformation bands have the trend to form the typical DRX microstructure with increasing the temperatures (might be caused by increasing testing temperatures or strain rates). Besides, the transformation bands can also be found in the sample compressed at 350 °C and 20 s^-1 when the temperature in the deformation alloy is high enough to activate non-basal slip and form DRX grains at local zone.

Abstract: In the present work, mechanical properties and microstructures of hot-rolled and solution-treated Fe-26Mn-6Al-1C steel (6Al steel) were investigated. Tensile tests were carried out at room temperature. The samples were characterized by using XRD, OM, SEM and TEM. The results suggested that the microstructure of the hot rolled 6Al steel was fully austenitic. After solution treatment and deformation, the microstructure was still single austenite. With the increase of the solution treatment temperatures, the strength decreased and the elongation increased. After solution treated at 1100°C for 1h, the yield strength, ultimate tensile strength and elongation were 378MPa, 756MPa and 57%.

Abstract: Based on rock Mechanical theory under unloading, according to the analysis of rock mechanics state of pre and post excavation of the layered dip rocky slope, it was found that excavation unloading cause deterioration of rock constitutive relation and structure plane’s mechanical parameters, deformation mechanism of high layered dip rocky slope was analyses when rock is at unloading condition in this study. Its deformation consists of the two parts which are rock mass unloading rock mass springback displacement and bedding-slip displacement along the rock mass discontinuity, and deduced the calculating formula of slope displacement. Research results with great guide significance and practical engineering value to similar engineering construction afterward.