Through thickness inhomogeneous microstructure and texture evolution in annealing process of cold-rolled TA18 tube

The evolution of microstructure and texture in commercially pure titanium has been studied as a function of strain path during rolling using experimental techniques and viscoplastic self-consistent simulations. Four different strain paths, namely unidirectional rolling, two-step cross rolling, multistep cross rolling, and reverse rolling, have been employed to decipher the effect of strain path change on the evolution of deformation texture and microstructure. The cross-rolled samples show higher hardness with lower microstrain and intragranular misorientation compared to the unidirectional rolled sample as determined from X-ray diffraction and electron backscatter diffraction, respectively. The higher hardness of the cross-rolled samples is attributed to orientation hardening due to the near basal texture. Viscoplastic self-consistent simulations are able to successfully predict the texture evolution of the differently rolled samples. Simulation results indicate the higher contribution of basal slip in the formation of near basal texture and as well as lower intragranular misorientation in the cross-rolled samples.

The evolution of texture and microstructure of commercially pure titanium during unidirectional rolling at room and cryogenic temperature was studied for two different initial orientations, namely RD (rolling direction)-split basal (BA orientation) and prismatic-pyramidal (PP orientation) till 90 pct rolling reduction. Effect of micro-mechanisms of deformation by slip and twinning on texture evolution and grain fragmentation was studied by employing characterization tools like bulk texture measurement using X-ray diffraction and electron back scatter diffraction. Both orientations yield split TD (transverse direction) texture for 90 pct rolling reduction at both the temperatures. Orientation BA showed severe twinning that saturated at deformation of 50 pct followed by slip dominated deformation, while orientation PP showed slip dominated deformation with marginal twinning throughout the rolling reduction at room temperature. Profuse twinning led to homogeneous grain refinement in orientation BA, while orientation PP showed heterogeneous grain refinement due to absence of twinning in some grains at the final stage of deformation. Rolling at cryogenic temperature enhances grain refinement due to extensive twinning that leads to weakening of texture in BA orientation and increase in intensity of texture for PP orientation compared to room temperature rolling. The evolution of microstructure and texture contributed to similar hardness for 90 pct room and cryogenic temperature rolled BA orientation, while 90 pct room temperature rolled PP orientation showed lower hardness.

An aluminium single crystal of cube orientation has been rolled to 15, 30 and 50% reductions under controlled homogeneous rolling conditions. The deformation structure of the rolled specimens was investigated by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) over several scales of magnification. The local crystallographic orientations have been measured by an automatic electron back scattering patterns (EBSP) technique and a semiautomatic TEM method. Orientation image maps based on the local orientation data have been used to reveal the evolution of the deformation structure during rolling. It is observed that by an opposite rotation around transverse direction (TD) the crystal was subdivided into four macroscopic bands, termed matrix bands in the present paper, which are parallel to the rolling plane. Between the four bands there are three transition bands in which the orientation changes continuously from that of a matrix band to that of the adjoining one. A model based on the idea of location–dependent shear strain caused by geometric and friction effects together with a plasticity analysis has been used to explain the macroscopic subdivision of the crystal. In addition to the macroscopic subdivision, a microscopic subdivision by the formation of cell–blocks within the matrix bands and a cell structure within transition bands has also been observed. A difference related to shear amplitude difference between the active slip systems changing continuously across the crystal has been observed. Both the macroscopic orientation of the dislocation boundaries and the misorientation angles and axes across dislocation boundaries are analysed and it is found that Frank9s formula is a useful tool in analysing the dislocation boundaries formed during deformation.

Microstructural inhomogeneities in polycrystalline copper was intentionally varied by the deformation at the liquid nitrogen temperature and the rolling without lubrication. The effect of different rolling conditions on the evolution of microstructure and texture during rolling and subsequent recrystallization was studied by means of X-ray texture measurement and microstructural observations. Applying cold rolling at a low temperature led to the formation of deformation twins in grains at the Cu-orientation, and shear bands developed when cold rolling was performed without lubrication. The evolution of the normal rolling texture was suppressed by deformation twinning. Shear bands in deformed structure resulted in a very weak cube-recrystallization texture.

Effect of heavy cryo-rolling on the evolution of microstructure and texture during annealing of equiatomic CoCrFeMnNi high entropy alloy

Present work addresses the evolution of texture and microstructure of equal channel angular extrusion (ECAE) processed AA 2014 Al alloy upto four passes at room temperature by adopting route BC. TEM is used to assess the microstructural changes during each ECAE pass. Texture measurements on samples of each pass were carried out by XRD technique. The evolution of texture components after each ECAE pass are analyzed and the changes are discussed with respect to the initial texture.

Analysis of the tensile behavior of a TWIP steel based on the texture and microstructure evolutions

Effects of strain rate on the microstructure evolution and mechanical response of magnesium alloy AZ31

Evaluation of Microstructure and Texture Development in Zr 1.0Nb Sheet during Cold-Rolling

Magnesium alloys are known to be one of the lightest structural alloys and hence they are of interest to the potential applications in aerospace and automobile industry. However, widescale commercial usage of magnesium alloys is limited given its low formability at room temperature. Conventional processing techniques fail to alter the formability and other mechanical properties significantly. A severe plastic deformation processing technique called friction stir processing (FSP) developed on the principles of friction stir welding (FSW) is touted to significantly change the microstructure, texture and hence the mechanical properties of magnesium alloys. This thesis is primarily based on investigating the mechanisms of microstructure and texture evolution during FSP of a commercial AZ31 magnesium alloy. The work presented in the thesis comprise of four projects, all under the broad theme of investigating the microstructure and texture evolution in AZ31 alloy: (i) Microstructural origin of friction stir processed zone in a magnesium alloy, (ii) Microstructural evolution during multipass friction stir processing of a magnesium alloy, (iii) Friction stir processing under different thermal history, and (iv) Study of grain structure evolution during annealing of a twin roll cast AZ31 Mg alloy. In (i) microstructural and texture evolution at the edge regions of a friction stir processed (FSP) magnesium alloy AZ31 was studied which was aimed at explaining the mechanism of the microstructural evolution during FSP. A model of microstructural development through grain boundary sliding of the ultra-fine grains was proposed based on the texture and microstructural observations in the concerned regions. Further, in (ii) the microstructure and texture developments and also prediction of texture using visco-plasticself-consistent (VPSC) modelling of commercial magnesium alloy AZ31 being friction stir processed through multi-pass and multi-directional (unidirectional, reverse and transverse tool movements) was studied. Later, in (iii) the effect of various coolant mediums viz. air, liquid nitrogen and water on the microstructural and thermal profiles in the friction stir processed zone was investigated. Experimental observations, on the process zone dimensions and temperature profiles, showed significant differences: which highlighted the effect of the thermal history. A numerical simulation was made using multi-physics finite element method. A three-dimensional steady-state coupled laminar fluid flow and heat transfer model was developed, which could capture the experimentally observed process zone dimensions and temperature profiles. Lastly, in (iv) evolution of microstructure under static annealing at 300°C and 500°C for different times of twin-roll-cast (TRC) magnesium alloy AZ31 was outlined. Grain path envelope analysis was used for quantitatively analyzing the microstructural evolution. Twin-rolled structure had bimodal grain size which was preserved after annealing at 300°C. However, annealing at 500°C led to a unimodal grain size. A deformation induced recrystallization recovery (DIRR) model was proposed which could explain the observed microstructural features. Thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy of the Indian Institute of Technology Bombay, India and Monash University, Australia.

A comprehensive description of processes occurring during the plastic deformation requires confrontation of the variation of texture with the accompanying changes in microstructure and physical properties. However, the variation of texture and microstructure in low stacking fault energy f.c.c, metals and alloys has not been till now well recognized as investigations were generally limited to texture analysis at high rolling reductions Not enough attention has also been paid to the effect of initial texture and grain size, and to the influence of geometry of the rolling gap on inhomogeneity of texture and microstructure. Equally, the commonly used method of series expansion for the quantitative description of texture does not allow a satisfactory identification of texture details, especially in lower levels of orientation density. The orientation distribution function is then burdened with truncation errors and those ensuing from the phenomenon of ghosts; the ghosts are observed in the ODF in the positions which are in twin relations with the pronounced components, and mechanical twinning is a very important process in the deformation of low stacking fault energy metals and alloys. In the present research the rolling has been carried on with unit draughts generally not much smaller than 0.5 and not greater than 5. In these conditi.ns the texture does not exhibit the through-thickness inhomogeneity-. Texture analysis has been carried out on samples from the central layer of the rolled material when applying the direct ADC method bae on discretization, in which the above described errors do not appear For all experiments the copper 8 wt pct germanium alloy was used, rolled from the annealed state up to 98 pct reduction. In the initial state the alloy was characterized by a rather sharp texture, and the mean grain size was 95 /m. The stacking fault _energy determined by the dislocation nodes method was equal to 10 mJ/m-.

Texture evolution and controlling of high-strength titanium alloy tube in cold pilgering for properties tailoring

It is well established that there is an interplay and interaction between the processing steps at fabrication of non-oriented electrical steels: hot rolling, cold rolling and annealing with respect to the evolution of the microstructure and texture. In this paper we will analyse in detail by optical microscopy and EBSD-measurements the influence of the microstructure of hot band prepared in different ways on the deformation structure after cold rolling and finally the evolution of microstructure as well as texture at final annealing due to recrystallization followed by grain growth. It will be demonstrated that the microstructure of the hot band effects the start of the recrystallization and finally the start of the grain growth at final annealing. The evolution of the microstructure at the stage of recrystallization is rather inhomogeneous across the thickness. This results from the complex deformation substructures after cold rolling. It will be pointed out that an explanation of the texture evolution at recrystallization only by in-plane compression stress fails. The inclusion of shear stress may explain the observed figure for the texture. The grain growth, which is necessary for the non-oriented electrical steels to reach the desired low values of specific magnetic losses, is finally the dominant process at the relevant higher annealing temperatures. The evolution of texture at recrystallization is different from those at grain growth.

Non-oriented grain type electrical steels are used mainly in electrical rotating machines such as motors and compressors, in which the magnetization direction rotates 360 ° every cycle while remaining in the plane of the plate. The performance of these devices is affected by crystallographic texture of electrical steels due to strong anisotropy of magnetic properties. The electrical steel is supplied in the form of plates which are processed by cold rolling and subsequent annealing. Both, cold rolling and annealing directly influence the formation of crystallographic texture components. During annealing, recrystallization occurs, and this phenomenon gives rise to changes in texture that influences the quality of the final product and its application. Several works have been published in the study of the evolution of crystallographic texture and grain size in this type of electrical steel. In this work, samples have been taken in industrial conditions at various temperatures during the annealing in a coil box. Electrical steel samples cold rolled with reductions of 50% and 70% in thickness were removed during the process of annealing, and the evolution of texture with increasing temperature was studied. Aspects related to recrystallization, grain size and the evolution of texture and magnetic properties were discussed. Texture and recrystallization were studied by X-ray diffraction and electron backscatter diffraction (EBSD). The magnetic properties were measured in a vibrating sample magnetometer.

Microstructure and texture evolution in warm rolled API 5L X70 pipeline steel for sour service application