Transmission Electron Backscatter Diffraction Research Articles

Orderly nucleation and competitive growth behaviors of Ti-Al intermetallic compounds in Ti/TiAl3 diffusion couple under high temperature

Precipitation and growth of intermetallic phases during thermal processing play an important role in the formation and evolution of heterogeneous microstructure of Ti-Al intermetallic based alloys, which have not been adequately understood. Herein, we study the nucleation and growth behaviors of Ti-Al intermetallic compounds in Ti/TiAl3 diffusion couple based on high temperature annealing. We combine scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back-scatter diffraction (EBSD) to analyze the microstructure and crystallization behavior of newly-formed intermetallic phases. The experimental results showed that phase transformations of α-Ti → Ti3Al → TiAl → TiAl2 and TiAl3 → Ti2Al5 → TiAl2 occurred orderly during annealing at temperatures from 950 ℃ to 1150 ℃. Intermetallic compounds containing Ti3Al, TiAl, TiAl2 and Ti2Al5 were formed at Ti/TiAl3 interface and comprised four distinct single-phase layers. The newly-precipitated intermetallic grains usually presented certain crystallographic orientation relationships with the adjacent phases. Growth kinetics analysis indicated that the growth of intermetallic layers was governed by volume diffusion and grain boundary diffusion, respectively, during annealing at 950 ℃ and 1050 ℃. Both interfacial reaction and volume diffusion contributed to the growth of intermetallic layers at 1150 ℃. Besides, the competitive growth between different intermetallic phases was revealed. To provide more guidance for the design of high-performance Ti-Al intermetallic based alloys, the hardness and elastic modulus of the above intermetallic compounds were determined preliminarily in the current work.

Microstructures in shocked quartz: linking nuclear airbursts and meteorite impacts

Many studies of hypervelocity impact craters have described the characteristics of quartz grains shock-metamorphosed at high pressures of >10 GPa. In contrast, few studies have investigated shock metamorphism at lower shock pressures. In this study, we test the hypothesis that low-pressure shock metamorphism occurs in near-surface nuclear airbursts and that this process shares essential characteristics with crater-forming impact events. To investigate low-grade shock microstructures, we compared quartz grains from Meteor Crater, a 1.2-km-wide impact crater, to those from near-surface nuclear airbursts at the Alamogordo Bombing Range, New Mexico in 1945 and Kazakhstan in 1949/1953. This investigation utilized a comprehensive analytical suite of high-resolution techniques, including transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). Meteor Crater and the nuclear test sites all exhibit quartz grains with closely spaced, sub-micron-wide fractures that appear to have formed at low shock pressures. Significantly, these micro-fractures are closely associated with Dauphiné twins and are filled with amorphous silica (glass), widely considered a classic indicator of shock metamorphism. Thus, this study confirms that glass-filled shock fractures in quartz form during near-surface nuclear airbursts, as well as crater-forming impact events, and by extension, it suggests that they may form in any near-surface cosmic airbursts in which the shockwave is coupled to Earth’s surface, as has been proposed. The robust characterization of such events is crucial because of their potential catastrophic effects on the Earth’s environmental and biotic systems.

Influence of carbon additions on microstructures and mechanical properties in additive manufactured superalloys

Combined with scanning electron microscopy, transmission electron microscopy and electron backscatter diffraction, the effects of carbon contents on mechanical properties of nickel superalloys fabricated by laser metal deposition were studied.

Abu Hureyra, Syria, Part 1: Shock-fractured quartz grains support 12,800-year-old cosmic airburst at the Younger Dryas onset

A previous investigation revealed that shock-fracturing, a form of low-pressure shock metamorphism in quartz grains, can be produced during near-surface atomic airbursts and in cosmic impact structures, most likely at pressures lower than 8 GPa. This discovery implies that similar shock-fracturing may also form in quartz grains exposed to near-surface airbursts by comets and asteroids. Here, we investigate this hypothesis by examining quartz grains in a sedimentary profile from Abu Hureyra, a prehistoric archaeological site in northern Syria. This site was previously proposed to have experienced a nearby, low-altitude cosmic airburst at the onset of the Younger Dryas (~12,800 years ago). The Younger Dryas boundary layer (YDB) at Abu Hureyra has previously been shown to contain a rich assemblage of materials consistent in indicating a cosmic impact. These include anomalously high concentrations of melted micro-spherules displaying increased remanent magnetism; meltglass with low water content indicative of high-temperature melting; nanodiamonds, potentially including lonsdaleite; carbon spherules produced by biomass burning; black carbon or soot; total organic carbon; and abnormally high-temperature melted refractory minerals and elements, including platinum, iridium, chromite, and zircon. To further test this impact hypothesis, we searched for evidence of shocked quartz, a robust, widely accepted indicator of cosmic impacts. We used a comprehensive analytical suite of high-resolution techniques, including transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD), to examine and characterize quartz grains from the YDB layer at Abu Hureyra. Our analyses revealed the presence of quartz grains with sub-planar, sub-parallel, and sub-micron-wide intragranular fractures, most likely produced by mechanical and thermal shock or the combination of both. Furthermore, these fractures are typically filled with amorphous silica (glass), a classic indicator of shock metamorphism. Elemental analyses of the weight percentages of oxygen in the amorphous silica indicate that this could not have formed from the deposition of hydrated silica (e.g., opal and hyalite), which is enhanced in oxygen. Instead, the silica we observed is typically depleted in oxygen, consistent with melting under highly reducing conditions. The shock fractures in quartz grains also display Dauphiné twinning, which sometimes develops during the stress of high temperatures or pressures. This evidence is consistent with the hypothesis that the glass-filled fractures in quartz grains were produced by thermal and mechanical shock during a near-surface cosmic airburst at Abu Hureyra. These glass-filled fractures closely resemble those formed in near-surface atomic airbursts and crater-forming impact events.

Influence of Partitioning Temperature on Microstructure and Mechanical Performance of Medium Manganese Fe-C-Mn-Cu-Cr-Mo-Nb Steel

A hot-rolled medium manganese Q&P steel was annealed at an intercritical annealing temperature (670 °C) and quenched to four partitioning temperatures (300 °C, 280 °C, 260 °C, and 240 °C). The effect of the partitioning temperature on the microstructure and mechanical properties of the steel was studied. The microstructure evolution at different partitioning temperatures was characterized using scanning electron microscopy (SEM), a transmission electron microscope (TEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). The results showed that, as the partition temperature increased, the fractions and the size of the fresh massive martensite (M2) increased, the initial lamellar martensite (M1) was coarsened, and the amount of M1 decreased. Moreover, the amounts of lath-like retained austenite (RA) decreased and the amounts of bulky austenite increased. The tested steel partitioned at 260 °C had relatively greater fractions of RA, in which there were sufficient contents of carbon diffused from M1. Therefore, the test steel partitioned at 260 °C showed fine comprehensive mechanical properties. The combination of tensile strength and elongation reached 30.3 GPa.%, and its work-hardening plateau was the longest, showing excellent ductility as it had sufficient fractions of the retained austenite with good stability.

STRENGTHENING MECHANISM OF 15-5PH STAINLESS STEEL UNDER DIFFERENT AGING TEMPERATURES

The research described here was aimed at illuminating the variation in the strengthening mechanism of Cr15Ni5 precipitation hardening stainless steel (15-5PH stainless steel) processed at aging temperatures ranging from 440–610 °C. The variation in the tensile property corresponding to different aging processes was measured, and the microstructure features were further characterized using a transmission electron microscope (TEM) and electron back-scatter diffraction (EBSD). Results indicated that the strength contribution induced by grain-refinement strengthening, precipitation strengthening and dislocation strengthening corresponding to different aging temperatures varying from 470–610 °C were determined to be distributed in strength ranges of 296–345 MPa, 0–469 MPa and 97–803 MPa, respectively. The strength increments caused by different combinations of precipitation strengthening and dislocation strengthening were crucial for determining the final mechanical properties of the studied 15-5PH stainless steel.

Ferroelectricity and negative piezoelectric coefficient in orthorhombic phase pure ZrO2 thin films

A new approach for epitaxial stabilisation of ferroelectric orthorhombic (o-) ZrO2 films with negative piezoelectric coefficient in ∼ 8nm thick films grown by ion-beam sputtering is demonstrated. Films on (011)-Nb:SrTiO3 gave the oriented o-phase, as confirmed by transmission electron microscopy and electron backscatter diffraction mapping, grazing incidence x-ray diffraction and Raman spectroscopy. Scanning probe microscopy techniques and macroscopic polarization-electric field hysteresis loops show ferroelectric behavior, with saturation polarization of ∼14.3 µC/cm2, remnant polarization of ∼9.3 µC/cm2 and coercive field ∼1.2 MV/cm. In contrast to the o-films grown on (011)-Nb:SrTiO3, films grown on (001)-Nb:SrTiO3 showed mixed monoclinic (m-) and o-phases causing an inferior remnant polarization of ∼4.8 µC/cm2, over 50% lower than the one observed for the film grown on (011)-Nb:SrTiO3. Density functional theory (DFT) calculations of the SrTiO3/ZrO2 interfaces support the experimental findings of a stable polar o-phase for growth on (011) Nb:SrTiO3, and they also explain the negative piezoelectric coefficient.

Effects of Heat Treatment on Microstructure and Mechanical Properties of a Transformation-Induced Plasticity-Aided Economical Duplex Stainless Steel

In order to obtain steel with high tensile strength and elongation and good pitting resistance, the economical duplex stainless steel with and without the addition of tungsten (W) was prepared in this paper. The comparison and distribution of the two phases were controlled by optimizing the heat treatment process. The highest product of tensile strength and elongation of Cr19 series duplex stainless steel (DSS) DSS were obtained after solution treatment at 1050 °C for 5 min, up to 58692 Mpa%(876 Mpa * 67%), when the area f.raction of α was about 50.7%. The addition of tungsten reduces tensile strength due to the increased area fraction of α at 1050–1150 °C. Finer grain size leads to higher tensile strength after solution treatment at 1050 °C. The microstructure is characterized by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The steels exhibit an excellent transformation-induced plasticity (TRIP) effect after the solution treated is at 1050 °C, which may primarily be due to the existence of a more unstable austenite phase. The TRIP effect acts through the phase transformation of γ to α′-M during high deformation, and the orientation relationship of {111}γ || {110}α′-M & <110>γ || <001>α′-M belongs to the standard variants of Nishiyama–Wassermann relationship.

Shock compression and spallation damage of high-entropy alloy Al0.1CoCrFeNi

• The accurate Hugoniot equation of state of Al 0.1 CoCrFeNi. • Nanotwins are only observed at high shock stress. • Damage in the Al 0.1 CoCrFeNi is ductile in nature. • Void nucleation depends on GB misorientation and peak stress. Shock compression and spallation damage of a face-center cubic phase high-entropy alloy (HEA) Al 0.1 CoCrFeNi were investigated via plate impact experiments along with free surface velocity measurements. Postmortem samples were characterized with transmission electron microscopy and electron backscatter diffraction. The Hugoniot equation of state and spall strength at different impact strengths were determined. There exists a power-law relation between spall strength and strain rate. The spall strength of Al 0.1 CoCrFeNi HEA is about 50% higher than those of previously studied HEAs and comparable to those widely applied structural stainless steels at the same shock stress. Dislocation glide and stacking faults are the important deformation mechanisms in the Al 0.1 CoCrFeNi HEA. Nanotwins are only observed at high shock stress. Damage in the Al 0.1 CoCrFeNi HEA is ductile in nature. Voids are nucleated preferentially in grain interiors, and the intragranular voids show a strong dependence on grain boundary misorientation and peak stress.

Effect of Reprocessing on Microstructure and Corrosion Resistance of Zr-Sn-Nb Alloy

To study the effect of reprocessing on the microstructure and corrosion resistance of Zr-Sn-Nb alloy, the original plates of Zr-Sn-Nb alloy were hot-rolled, cold-rolled and recrystallized to obtain the reprocessed plates. The microstructure of both plates was observed with a scanning electron microscope (SEM), a transmission electron microscope (TEM) and electron backscattering diffraction (EBSD). The original plates and reprocessed plates were put into a static autoclave for 300 days in 360 °C/18.6 MPa water. The relationship between the microstructure and corrosion resistance of the Zr-Sn-Nb alloy was discussed. The coarse deformation grains with twins and fine recrystallized grains were obtained, and grain sizes became smaller. The Ostwald ripening of second phase particles (SPPs) happened, and the average size of SPPs increased. Some SPPs changed from an HCP structure to an FCC structure. Reprocessing made the transition advance, which is related to the accelerated evolution of cracks in the oxide film and the increase in metal-oxide film interface roughness. The deterioration of corrosion resistance is closely related to the change of grain size, SPP size and SPP structure.

Epitaxy of single-crystalline GaN films on novel Ca3Ta(Ga0.5Al0.5)3Si2O14 substrates by metal-organic chemical vapor deposition

The langasite (La3Ga5SiO14, LGS) is a nearly lattice-matched substrate for epitaxy of GaN films. However, it is a challenge to grow GaN films on LGS substrates by metal-organic chemical vapor deposition (MOCVD) because LGS is unstable in aggressive gas atmosphere at high temperature of ∼1000 °C. To overcome the problem, this study chooses another LGS family crystal Ca3Ta(Ga0.5Al0.5)3Si2O14 (CTAGS) which has the same crystal structure as LGS and is more stable in high temperature. The morphology of GaN films at different growth stages are characterized and the results show continuous and smooth GaN films could be obtained after growing for 3 h. Single-crystalline GaN films are determined by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) measurements. The epitaxial relationship between GaN and CTAGS is GaN(0001)//CTAGS(0001) and GaN(101¯0)//CTAGS(213¯0), the lattice mismatch between GaN and CTAGS is 4.15%. The work is great potential in promoting the development of GaN-based devices.

Characterization of hot extrusion deformation behavior, texture evolution, and mechanical properties of Mg–5Li–3Sn–2Al–1Zn magnesium alloy

The effects of four different hot extrusion processes on the microstructure, texture, and mechanical properties of Mg–5Li–3Sn–2Al–1Zn alloys were investigated with the help of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) techniques. The results show that the magnesium alloy experienced dynamic recrystallization during the hot extrusion processes, the grain size was significantly refined compared with that of the cast alloy, and the mechanical properties of the alloy were significantly improved. After the 105° forward-parallel channel extrusion process, the alloy exhibited optimal strength and plasticity with 178 MPa, 270 MPa, and 21.03% for tensile yield strength, ultimate tensile strength, and elongation, respectively, which were 61.8%, 44.4%, and 134.4% higher compared to the homogeneous state. The increase in strength is attributed to fine grain strengthening, while the significant increase in plasticity is due to the weakening of the basal texture and the improved coordination of plastic deformation of the magnesium alloy following grain refinement.

Phase evolution characteristics, thermal stability, and strengthening processes of Fe–Ni based ODS invar steel produced by mechanical alloying and spark plasma sintering

In the present study, the base composition of Fe-42 wt% Ni invar was used to prepare three different oxide dispersion strengthened (ODS) steel compositions with addition of 2 wt% Y2O3 and a varying amount of Ti (0.3%, 1%, and 2% wt.%) by mechanical alloying (MA) using SPEX8000 M high energy ball mill. The mechanically alloyed samples were compacted first to make pellets, and batch-annealed at 400, 600, 800, and 1000 °C to verify its thermal stability. The hardness of the as-milled and annealed samples was estimated to apprehend the effect of Ti content and temperature on the mechanical properties. Phase evolution was studied by using the x-ray diffraction (XRD) technique of the as-milled and annealed samples of all the compositions. Then, all the milled samples were spark plasma sintered (SPSed) at 1000 °C for further investigation of sintering characteristic, microstructure, and mechanical properties. The SPSed samples were subjected to compression and Vickers hardness testing to study the change in mechanical properties of the different compositions after sintering. Yield strength values of the three compositions were theoretically calculated through strengthening mechanisms analysis using XRD data and microstructural information of the SPSed samples and correlated with the experimentally determined compressive yield strength. The microstructural study of the SPSed samples was performed using transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) analysis. The relationship between microstructure and mechanical properties has been examined in the context of various strengthening processes such as dislocation strengthening, solid solution strengthening, grain size strengthening, and precipitation/dispersoid strengthening in the SPSed alloys.

Discussion on the presence condition of suboxide ZrO beneath the oxide in zirconium alloys

Characteristics related to the oxide-metal interface of oxidized (corroded) zirconium alloys in an autoclave have been extensively explored using both experimental and theoretical methods during the last ten years. A thin intermediate or suboxide layer with an approximate 1:1 ZrO stoichiometry was observed at the oxide-metal interface in several zirconium alloys. Through investigating its chemical composition, morphology, grain size and orientation relationship with the substrate α-Zr, some researchers assumed that the suboxide layer is related to the oxidation (corrosion) rate, whereas others did not. The majority of earlier studies used aqueous corrosion samples that were exposed to high pressure and low temperature, simulating in-service conditions. However, the interfacial characteristics at higher temperature have been scarcely reported. In this study, we focused on the microstructure and micro-chemistry of the oxide and suboxide ZrO in Zircaloy-4 and Zr-1.0Nb-0.01Cu oxidized at 650–1000 °C by combining Backscattered Electron (BSE) mode in Scanning Electron Microscope (SEM), Transmission Electron Backscatter Diffraction (t-EBSD) and (Scanning) Transmission Electron Microscope fitted with an Energy Dispersive X-ray Spectroscope ((S)TEM-EDS). The results show that the suboxide ZrO in oxidized Zircaloy-4 and Zr-1.0Nb-0.01Cu alloys has different morphologies. With increasing oxidation temperature, the suboxide ZrO distribution varies significantly, from a continuous layer to a few occasional blocky grains, until any ZrO grains are undetectable at the ZrO2/α-Zr(O) interface. The hexagonal crystallographic structure of ZrO has also been confirmed. According to discussions combining our investigations and earlier reports, the presence of suboxide ZrO and their morphology are probably related to the oxidation temperature, chemical composition of alloys and complex stress accumulation adjacent to the interfacial region.

Influence of Mo on the dynamic recrystallization behavior of Al–Cu–Mg–Ag alloy

High-throughput double cone specimens were used to study the influence of Mo on the microstructure evolution of Al–Cu–Mg–Ag alloy under a wide range of strain along the axis. The microstructure evolution was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). Results demonstrated that Al6(Fe, Mn, Mo) dispersoids formed in the Al–Cu–Mg–Ag alloy with the addition of 0.2% Mo during double-step homogenization. Meanwhile, rod-like Al20Cu2Mn3 and disk-like Al6(Fe, Mn, Mo) dispersoids segregated to opposite distribution in interdendritic regions and dendrite cores, respectively, which obviously eliminated the dispersoid-free zones and intragranular sparse regions. With different effective strains along the axis, Al6(Fe, Mn, Mo) dispersoids obviously reduced the transformation from Low-angle grain boundaries to High-angle grain boundaries. The nucleation and growth of dynamic recrystallization grains were effectively inhibited by the coupling of Al20Cu2Mn3 and Al6(Fe, Mn, Mo) dispersoids due to the obstruction of dislocation movement.

Theoretical Diffraction Pattern Characteristics of Cubic Twin Crystal

Twin crystal is a common lattice arrangement of crystal structure. The commonly used characterization methods for crystal structure include transmission electron diffraction (TED) pattern and electron backscatter diffraction (EBSD) pattern, but there is currently no specific reference standard for twin crystal. In this research, the mathematical relationship between crystal structure and TED and EBSD patterns of twin was calculated. The characteristics of twin electron diffraction spectrum, as well as the calibration of TED and EBSD patterns, were discussed and analyzed towards the examples of face-centered cubic crystal and body-centered cubic crystal. Overall, our results establish a theoretical calculation standard of diffraction spectrum, which provides a reference for further explorations to characterization of twin crystal structures.

Deuterium permeation behavior in a FeCrAl-based alloy containing Mo, Nb and Ta elements for LWR cladding application

The deuterium permeation behavior of a FeCrAl-based alloy containing Mo, Nb and Ta elements was investigated by gas-phase deuterium permeation testing, transmission electron microscopy, X-ray diffraction and electron backscatter diffraction methods. The results show that the higher the test temperature, the greater the steady-state permeation flux of the FeCrAl-based alloy. As the upstream deuterium pressure increases, the steady-state permeation flux of the FeCrAl-based alloy also increases. The pressure exponent n is between 0.5 and 1, indicating that deuterium permeation in the FeCrAl-based alloy is controlled by a combination of bulk diffusion and surface processes. This phenomenon is caused by the oxide film generated on the surface of the FeCrAl-based alloy during deuterium permeation test. The deuterium permeability of the FeCrAl-based alloy is about 37 times that of 316 L and 95 times that of Zircaloy-4 at the typical operating temperature of 300 °C. At 360 °C, the deuterium permeability of the FeCrAl-based alloy is about 25 times that of 316 L, and about 32 times that of Zircaloy-4. Compared with 316 L and Zircaloy-4 alloy, the activation energy of deuterium permeation of the FeCrAl-based alloy is smaller, indicating that deuterium permeates more easily in the FeCrAl-based alloy. The activation energy of deuterium diffusion in the FeCrAl-based alloy is also smaller, indicating that deuterium diffuses more easily in the FeCrAl-based alloy.

Effect of strain-induced martensite reverse transformation on microstructure evolution and electrochemical behaviour of 2304 lean duplex stainless steel

ABSTRACT The effect of strain-induced martensitic transformation (SIMT) and its reversion (SIMRT) on the microstructure evolution and localised corrosion of 2304 lean duplex stainless steel (LDSS) was investigated. The cold-rolled LDSS was subjected to reverse annealing at 600°C to 900°C for 1800 s. To evaluate the microstructure, scanning (SEM) and transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) were used as the main techniques. Subsequent electrochemical characterisation included cyclic polarisation and double loop-electrochemical potentiokinetic reactivation test. SIM formation was noticed after cold rolling, and a partial reverse transformation was seen after annealing at 600°C. At 600°C, SIMRT led to decrease in pitting resistance and increase in the degree of sensitisation (DOS). Increasing the annealing temperature favoured localised and intergranular corrosion resistance. The obtained results indicate that reversed austenitic and recrystallised grains have a beneficial effect on desensitisation and corrosion resistance of 2304 LDSS.

Micro-crystallographically unraveling strength-enhanced behaviors of the heavy-thick Ti-6Al-4V welded joint

Developing high-strength welded joint of heavy-thick titanium alloy plates is in immediate need to unravel the strength-enhanced behaviors for high-pressure and low-temperature performance of deep-sea submersibles. Here, we synergistically employed transmission electron microscope (TEM) and electron back-scattered diffraction (EBSD) technologies to micro-crystallographically unravel the evolution behaviors of weld microstructure, grain orientation and grain boundaries for the welded joint of the heavy-thick Ti-6Al-4V plates with the thickness of up to 60 mm. Resulted, the strength-enhanced welded joint was evidently ascribed to the transformation of lath martensite into basketweave-martensite and the rigid-flexible mixture strategy of the enhanced conical-texture and the weakened basal-texture and cylindrical-texture. Furthermore, the remarkably lowered geometrically necessary dislocations (GNDs) density and the greatly decreased deformation-prone grains number due to the transformation of low-into-high angle grain boundaries indispensably strengthened the joint strength. Therefore, this work has made clear the strength-enhanced behaviors of Ti-6Al-4V welded joints for substantially improving high-strength welded structure of heavy-thick titanium alloy plates, and sufficiently promoting the service safety for deep-sea submersibles. • Transformation of lath martensite into basketweave-martensite enhanced the welded joint strength. • Thermal cycling caused the rigid-flexible mixture of the enhanced conical-texture and the weakened basal-texture. • Transformation of low-into-high angle grain boundaries lowered GNDs density and decreased deformation-prone grains number.

The role of primary α grains in the degree of transformation texture obeying the Burgers orientation relationship in Zr alloys

The microstructure and texture evolution of Zr-xNb-0.4Mo (x = 0, 0.2, 0.4, 0.6 and 1.0 wt%) alloys are characterized using scanning electron microscopy (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) technique. The aim is to elucidate the role of primary α grains in the degree of transformation texture obeying the Burgers orientation relationship (OR) in Zr alloys. The primary α grain is produced by adjusting Nb content in Zr alloys. The crystallographic orientations of Zr-xNb-0.4Mo alloys show that the degree of transformation texture obeying the Burgers OR increases with the proportion of primary α grains decreasing. Until no primary α grains exist, the transformation texture obeys the Burgers OR strictly. The primary α grains can exert great influence on variant selection by restricting the growth of high-temperature β grains and acting as nucleation sites. The fact that primary α grains are the origins of variant selection is observed. Meanwhile, variant selection occurs in both the duplex microstructure and full martensite plates during the water-quenching process. The texture weakening of the duplex microstructure is attributed to the new texture components given by martensite plates. In terms of microstructure, a series of precipitates, Zr3(Nb, Mo, Fe), are found in a primary α grain.