R.K. Ray

Effects of composition and processing parameters on precipitation and texture formation in microalloyed interstitial free high strength (IFHS) steels

Abstract Precipitation in IFHS steels affects texture formation during annealing, which in turn determines the formability. The single most important type of precipitates in IFHS steels is FeTiP. Precipitation of FeTiP leads to the decrement in the intensity of the favourable {111} texture, which causes a degradation of the formability properties. The batch annealed steels are particularly susceptible to this. Since formation of FeTiP as well as of the other types of precipitates in IFHS steels is dependent on steel composition and processing parameters, a detailed and systematic investigation is urgently needed to look into the various aspects of precipitation in IFHS steels. Proper scientific investigation is expected to provide necessary processing windows that will not allow formation of unwanted precipitates. This will help in maximising the strengthening effects of P, without any degradation of the deep drawability of the steels.

Microstructure and Texture Evolution in Interstitial-Free (IF) Steel Processed by Multi-Axial Forging

In this study, severe plastic deformation (SPD) of Ti-bearing interstitial-free steel was carried out by multi-axial forging (MAF) technique. The grain refinement achieved was comparable to that by other SPD techniques. A considerable heterogeneity was observed in the microstructure and texture. Texture of multi-axially forged steels has been evaluated and reported for the first time. The material exhibited a six-fold increase in the yield strength after four cycles of MAF.

Recrystallization in a low-density low-alloy Fe–Mn–Al–C duplex-phase alloy

The recrystallization behaviour of a cold-rolled, low-density, low-alloy duplex-phase alloy (Fe–6.57Al–3.34Mn–0.18C, wt.%) has been studied. Temperature-resolved X-ray diffraction and dilatometry showed that the alloy recrystallizes at 850 °C during continuous heating. However, electron back-scattered diffraction investigations using Kernel average misorientation revealed that during annealing ferrite recrystallizes at lower temperatures while austenite remains strained up to 1200 °C. This study underlines the complexity of recrystallization of a microstructure comprising of constituents with high and low stacking fault energy.

Phase transformation behaviour in two C–Mn–Si based steels under different cooling rates

Abstract The continuous cooling transformation (CCT) behaviour of two C–Mn–Si based steels was investigated. The effects of chemical composition and cooling rate on γ→α transformation were studied using dilatometric measurements. Quantitative phase analysis was carried out in order to determine the effect of cooling rate on the precise phase distribution after transformation. Presence of Cr and Mo in the experimental steels appears to retard pearlitic transformation and promotes formation of acicular products (combination of acicular ferrite, Widmanstatten ferrite and bainite). Martensitic transformation also starts at a perceptibly lower cooling rate in the Mo containing alloy as compared with the one without any Mo.

Precipitation and Texture Formation in Interstitial Free High Strength (IFHS) Steels: A Short Review

Interstitial free high strength steels (IFHS) are widely used in the automobile sector due to their high strength and excellent formability. However, these properties of IFHS steels are very much dependent on the processing parameters, like hot rolling, cold rolling and annealing. The composition and processing parameters influence the chemistry and morphology of the precipitates formed in these steels, which in turn control the texture and thus the deep-drawability. This review will briefly summarize the findings of the ongoing research in this area. An attempt will also be made to elucidate the correlation of precipitation behavior and texture formation (and thus formability) in these steels.

Microstructure, texture, grain boundary characteristics and mechanical properties of a cold rolled and annealed ferrite–bainite dual phase steel

Abstract The microstructural, textural evolution and changes in grain boundary character distribution during annealing of a prior cold worked (30 %, 50 % and 80 %) ferrite–bainite dual phase steel have been studied and correlated with mechanical properties. It has been shown that submicron sized subgrains can be obtained by selecting the appropriate amount of cold rolling and annealing cycle. Increasing the annealing temperature in all the materials produces the expected results, namely decrease in strength with a simultaneous increase in ductility. Although reasonably sharp γ-fibres were obtained in 80 % cold rolled and its 500 °C annealed counterpart, the very low values (< 1.0) make the steel unsuitable for the purpose of deep drawing. It is envisaged that grain boundary engineering may lead to better strength–ductility combinations in this steel for an enhanced range of applications.

Correlation between substrate steel texture and coating texture of two industrially produced galvanised and galvannealed steels

Abstract The substrate steel texture appears to control the texture of galvanised and galvannealed coating on steels. The ratio of the volume fraction of {113} and {111} orientations of the substrate steel may be important in controlling the texture of the overlying coating.

Texture Evolution in Thin Films

Thin films of metals, ceramics, or polymers find many applications in electronic, magnetic, and optical devices. Thin films are usually characterized by the presence of very sharp crystallographic textures. In fact, it is rather difficult to produce thin films without texture.

Experimental Determination of Texture

The previous chapter describes how texture of a material can be represented in terms of pole figures and ODFs. These methods of representation require the basic orientation data to be obtained from the crystallites or grains, which constitute the material. This chapter will deal with the different experimental techniques that are employed for this purpose.

Textures of Non-metals

The preceding chapters mainly dealt with texture formation in metallic materials. However, textures do form in non-metallic materials also during processing. The mechanism of texture evolution in non-metals is similar to that in metals. Although the method of texture measurement is essentially the same for all crystalline materials, however, non-metallic materials pose some complications in the measurement technique.