Formation Of Subgrain Boundaries Research Articles

The Nanoparticle-induced Zener Pinning Effect on Strain-softening in a Cold-Worked Cu-Al2O3 Composite with 0.1 wt.% Al Content

The thermo-stability of microstructure during isothermal annealing at 900 °C and 1000 °C in a cold-worked Cu-Al2O3 composite with 0.1 wt.% Al content and its effect on resistance to softening were investigated in this paper. The results reveal that the microstructure following cold deformation consists of a Cu matrix with a refined grain size and high-density dislocations, accompanied by dispersed Al2O3 nanoparticles exhibiting an extremely low volume fraction. During isothermal annealing at 900 °C, the Al2O3 nanoparticles can strongly restrict the migration of the dislocations and suppress the recrystallization of the fine-grained Cu matrix by the Zener pinning effect. Furthermore, the presence of pinned dislocations facilitates the formation of sub-grain boundaries comprising high-density dislocations. Consequently, the Cu-Al2O3 composite with 0.1 wt.% Al content exhibits remarkable thermo-stability in its microstructure due to the incorporation of Al2O3 nanoparticles, resulting in a significantly elevated softening temperature of up to 1000 °C and thereby demonstrating excellent resistance against softening. However, the observed phenomenon of softening after isothermal annealing at 1000 °C for 5 hours can be attributed to extensive recrystallization growth that promotes twin boundary formation, primarily caused by the weakening Zener pinning effect resulting from Oswald ripening of Al2O3 and rod-like Al2O3 formation.

Exploring high-temperature deformation and damage behaviour in high-performance ferritic (HiperFerSCR) steel with Laves phase particles

The mechanical behaviour at high temperatures and the corresponding microstructural characteristics of a newly developed high-performance ferritic, salt-corrosion-resistant (HiperFerSCR) steel containing Laves phase particles were studied to investigate the active deformation mechanisms and the evolution of damage. A series of tensile tests were conducted at both room temperature and elevated temperatures (550, 600, and 650 °C), along with detailed microstructural analyses using scanning electron microscopy and electron backscatter diffraction. The tensile flow characteristics of HiperFerSCR at room temperature exhibit significant strain hardening, which is due to the Laves phase particles that encourage planar slip, demonstrated by the formation of numerous slip bands and low-angle grain boundaries. The intersections of these slip bands with grain boundaries appear to be the initiation sites for cracks, which then propagate intergranularly as well as within grain interiors along the slip bands. At high temperatures, the flow characteristics show strain softening, which is attributed to a dynamic recovery (DRV) mechanism, evident in the formation of subgrain boundaries decorated with Laves phase particles. During high-temperature deformation, damage initiates in the particle-free zone (PFZ), which expands at higher temperatures, leading to strain localisation, void formation along the grains, and eventually, grain boundary decohesion.

Analyzing dynamic strain aging and yield strength anomaly in IN740H, a nickel-based superalloy comprising low volume fraction of γ′

IN740H, a Ni-based superalloy comprising a low volume fraction of γ′, is a promising material for superheater and reheater components in advanced ultra-supercritical (AUSC) power plants. Here, its tensile deformation behavior across a temperature range of 25–800 °C and strain rates of 10−3 to 10−5 s−1 was investigated. Distinct stress-strain curve serrations, consistent with dynamic strain aging (DSA), were predominantly observed between 400 and 600 °C. At lower temperatures and strain rates, Type E serrations appeared, which transitioned to Type B and then to Type B + C serrations with increasing temperature. At 600 °C, Type B serrations emerged at high strain rates, gradually transforming into Type B + C serrations as rates decreased before disappearing at lower rates. Notably, the alloy displayed negative strain rate sensitivity in the DSA regime. Furthermore, the alloy also showed yield strength anomaly (YSA), wherein the yield strength decreased initially with temperature, followed by an increase above a specific temperature. Fractography reveals a transition from transgranular dimple fracture behavior to intergranular fracture behavior with an increase in temperature. Post-deformation electron backscatter diffraction analysis indicated predominant grain alignment along {100} and {111} planes, such that {111}-oriented grains exhibited a lower Schmidt factor and the formation of fewer sub-grain boundaries. This work comprehensively characterizes DSA and YSA in IN740H in the temperature range relevant to AUSC power plants, thereby providing much-needed information to assess its potential suitability for applications under harsh conditions.

Development and characterization of a low-density TiNbZrAlTa refractory high entropy alloy with enhanced compressive strength and plasticity

A new refractory high entropy alloy (RHEA) is designed by combining refractory elements Nb and Ta with Ti, Zr, and Al, resulting in a (TiNbZr)89(AlTa)11 alloy composition with a low-density of 6.0 g/cm3. The novel RHEA features a BCC matrix with B2 and Zr5Al3 nano precipitates, exhibiting a compressive yield strength of ∼890 MPa and specific yield strength of ∼148.3 MPa g−1 cm3. Remarkably, the alloy demonstrates excellent compressive plasticity of ∼70% at 298 K. As the temperature increases to 873 K, 1073 K, and 1273 K, the yield strength of the RHEA gradually decreases to ∼610 MPa, ∼ 210 MPa, and ∼ 60 MPa, respectively. These results indicate that this novel RHEA showcases a combination of good specific strength and plasticity. Post-compression, B2, and Zr5Al3 phases are observed. The second-phase particles dispersed throughout the grains hinder dislocation motion and contribute to the formation of sub-grain boundaries during hot compression.

Dynamic α globularization in laser powder bed fusion additively manufactured Ti-6Al-4V

As a dual-phase α+β titanium alloy broadly used in the aerospace and biomedicine sectors, Ti-6Al-4V offers a variety of attractive mechanical properties imparted by its tailorable microstructures typically developed via thermomechanical processing. Such a capability in microstructural control, however, is still beyond the reach of laser powder-bed fusion (LPBF) additive manufacturing (AM) of Ti-6Al-4V. Here we demonstrate for the first time the development of near-equiaxed α microstructure in situ via dynamic globularization in the as-built state of LPBF Ti-6Al-4V. Akin to globularization during thermomechanical processing, the globularization process during LPBF is also governed by a series of mechanisms such as sub-grain boundary formation, boundary splitting, thermal grooving, lamellar termination migration and epitaxial growth. This is largely driven by continuous introduction of excess dislocations at the mismatched α/β interphase boundaries while the α↔β phase transformation takes place repeatedly during LPBF. The findings in this study provide new knowledge towards the development of a holistic microstructural control strategy in additively manufactured Ti-6Al-4V.

Influence of annealing on recrystallization and mechanical properties of Zr702 alloy obtained by accumulative roll bonding

The influence of annealing time on the recrystallization evolution and mechanical behavior of Zr702 alloy obtained by accumulative roll bonding (ARB) has been investigated. Results show that the bonding degree of the ARB interface gradually improved with the increase of annealing time from 5 to 20 min, which is because the atoms can obtain relatively more diffusion driving force with the increase of annealing time. In addition, almost complete recrystallization (average size of about 3.98 μm) and excellent comprehensive mechanical properties can be obtained as the annealing time is set to 20 min, and the evolution path of the microstructure with annealing time can be described as: (I) high density stacking dislocations; (II) formation of subgrain boundaries; (III) reduction of dislocation density and formation of recrystallization; (IV) growth of recrystallized grains. In this study, with the increase of annealing time, the release of deformation storage energy and the increase of recrystallized dislocation-free grains are very helpful to improve the ductility.

Microstructure evolution mechanism of tungsten induced by ultrasonic elliptical vibration cutting at atomic/nano scale

Ultrasonic elliptical vibration cutting (UEVC) technology has been utilized for ultra-precision machining of difficult-to-machine metal materials such as tungsten. Nevertheless, the microstructure evolution mechanism of tungsten under the synergistic effect of ultrasonic and mechanical loads remains unclear, particularly at the atomic/nano scale. Additionally, the plastic deformation mechanism of tungsten differs from that of other metallic materials due to its low dislocation mobility (brittle at room temperature). Hence, the molecular dynamics simulation of UEVC for single crystal tungsten was established to study its mechanisms in plastic deformation and microstructure evolution under stress induction in this study. The results indicated that the main plastic deformation mechanisms including dislocation slip, amorphous phase transformation and nanocrystal were found during the tungsten removal, and accompanied by some extent of lattice distortion. The instantaneous shear stress of UEVC reached 16.88 GPa. Compared with common cutting (CC), the formation of nanocrystals mainly occurred in UEVC because the instantaneous shear stress exceeded the critical shear stress of multiple slip systems during cutting. Similarly, the high dislocation density and high plastic deformation degree of the machined zone in UEVC were also attributed to the high shear stress. The dynamic recrystallization of tungsten induced by UEVC was realized from dislocation slip to the formation of dense dislocation walls, followed by the formation of sub-grain boundaries, and finally to the formation of nanocrystals.

In Situ Observation of CGHAZ Microstructure Evolution of Hot‐Rolled Ship Plate Steel Containing 0.012 Yttrium under High‐Heat‐Input Welding

The laser scanning confocal microscope is used to simulate the microstructural evolution of a coarse‐grained zone composed of hot‐rolled ship steel with yttrium under high‐energy input welding. The results demonstrate that Y2O3 near the austenite grain boundary can effectively block the overall migration of the austenite grain boundary during the application of the welding heating process. Additionally, the presence of Y2O3 in the austenite grain can promote the formation of new grain and subgrain boundaries, thereby refining the austenite grain. During the postweld cooling process, the undercooling degree is high under a lower heat input, and the phase variation occurs along the direction at a large angle to the proto‐austenite boundary. Thus, a large amount of acicular ferrite (AF) is formed perpendicular to the proto‐austenite boundary. Based on the first principle, Y2O3 can be used as the nucleation site for AF phase transformation to promote the formation of a fine interlocking structure. However, its impact is limited because the cooling rate significantly affects the microstructure evolution of the coarse‐grain zone of the weld during welding with a high heat input.

The microstructure and mechanical properties of 316L austenitic stainless steel prepared by forge and laser melting deposition

In this study, the 316L austenitic stainless steel blocks were prepared by forge and laser melting deposition (LMD). To clarify the effect of deposition strategy on microstructure and mechanical properties of 316L samples, three different deposition strategies (30°, 67° and 90°) are selected. The results showed that the molten pool of LMDed sample consists of a large number of coarse columnar grains and a few irregular equiaxed grains, which contains plentiful cellular and fiber sub-structures with an average size of ∼4 μm. The LMD process can significantly improve the comprehensive mechanical properties perpendicular to the build direction of 316L austenitic stainless steel, which was mainly attributed to sub-structural strengthening, but also slightly due to the local misorientation and texture distribution. The yield strength and ultimate tensile strength of R90 sample increased to 484.0 MPa and 627.6 MPa from 305.3 MPa to 601.4 MPa of as-forged 316L, and its elongation has a negligible reduction. The sub-structures produced during solidification have the same fine grain strengthening effect as the high-angle grain boundary, and the yield strength and average size of sub-structures conform to the Hall-Petch relationship. The deterioration of the plastic deformation capacity of the R67 sample is attributed to the larger thermal stress and texture distribution with a certain hard orientation. The plastic deformation of as-forged sample is mainly coordinated by multi-system slip, while twinning and slip are activated together during deformation of LMDed 316L austenitic stainless steel. The grain boundary map indicated that the strain location preferentially appears along cell wall of sub-structures, which promotes the formation of sub-grain boundaries during deformation of LMDed samples.

X-ray diffraction line broadening and radiation damage

The diffraction line profiles of single crystal Zr and Zr-2.5Nb pressure tubing have been measured and analysed before and after irradiation in a nuclear reactor. The irradiation produces damage in the form of prismatic dislocation loops. In all cases, Fourier analysis of the deconvoluted peak using the method of Warren and Averbach shows that the magnitude of the distortion (micro-strain) component is not consistent with the dislocation density measured by transmission electron microscopy. The discrepancy can be related to the reduced strain energy from the dipoles on opposite sides of the prismatic dislocation loops and loop alignment, which reduces the average strain in the same way as polygonization or sub-grain boundary formation. The Fourier analysis also gives a value for the coherent diffraction domain size that is consistent with the mean spacing between the dislocations and thus the dislocation density.

Mechanistic investigation on Ce addition in tuning recrystallization behavior and mechanical property of Mg alloy

Constructing bimodal grain structure is a promising approach to achieve the high strength-ductility synergy in Mg alloy. Formation of bimodal grain is closely related to the dynamic and/or static recrystallization process, which has not been fully understood in the typical Mg-RE based alloy. In this work, it is claimed for the first time that the minor Ce addition (∼0.3 wt%) into Mg matrix significantly promotes the pyramidal <c+a> and non-basal <a> dislocations at the early stage of extrusion, which consequently enhances the formation of sub-grain boundaries via the movement and recovery of pyramidal II-type <c+a> dislocations. At this stage, fine sub-grain lamellae are widely observed predominantly due to the low migration rate of sub-grain boundary caused by the limited mobility of <c+a> dislocations. At the later stage, the sub-grains continuously transform into dynamic recrystallized (DRXed) grains that have 〈101¯0〉 Taylor axis and also strong fiber texture, indicating substantial activation of pyramidal II-type <c+a> dislocation. The low mobility of <c+a> dislocations, accompanied with the solute drag from grain boundary (GB) segregation and pinning from nano-phases, cause a sluggish DRX process and thus a bimodal microstructure with ultra-fined DRXed grains, ∼0.51 µm. The resultant texture hardening and grain refinement hardening effects, originated from bimodal microstructure, result in a yield strength of ∼352 MPa, which is exceptional in Mg-Ce dilute alloy. This work clarifies the critical role of Ce addition in tuning recrystallization behavior and mechanical property of magnesium, and can also shed light on designing the other high-performance Mg alloys.

Microstructural response and surface mechanical properties of TC6 titanium alloy subjected to laser peening with different laser energy

In this paper, the main purpose was to investigate the effects of laser peening (LP) on the microstructural evolution and frictional wear resistance of TC6 titanium alloy. The surface topographic features, microhardness and residual stress distribution in the depth direction of differently treated specimens were measured using three-dimensional topography instrument, digital microhardness tester and residual stress instrument. The frictional wear test was carried out using a multifunctional friction wear tester. Meanwhile, X-ray diffraction (XRD), optical microscope (OM) and transmission electron microscopy (TEM) were utilized to investigate the effects of LP on the microstructural response of TC6 titanium alloy. The results indicated that the micro-pits induced by LP increased the surface roughness to a maximum of 6.94 μm. LP technique effectively improved the microhardness and frictional wear resistance of TC6 titanium alloy, and the wear form changed from abrasive wear, adhesive wear and fatigue spalling wear to abrasive wear at the laser energy of 8 J. Compared to the untreated specimens, the surface microhardness of the specimens treated by LP with 8 J increased from 356 HV to 442 HV, and the affected layer depth was approximately 500 μm. Moreover, the friction coefficient decreased from 1.2 to 0.5, the abrasion depth of the abrasion track was reduced by approximately 32 % compared to the untreated specimen. Additionally, the surface compressive residual stress induced by LP with 8 J reached about −510 MPa. The microstructural evolution of the specimens processed by LP was dominated by twin formation and dislocation slip, while the intercalation between multidirectional twins and the formation of sub-grain boundaries promoted grain refinement of TC6 titanium alloy. Refined grains, high density of dislocations, mechanical twins and the implantation of compressive residual stresses effectively improved the friction and wear resistance of TC6 titanium alloy.

Effect of split sleeve cold expansion on microstructure and fatigue performance of 7075-T6 aluminum alloy holes

7075-T6 aluminum alloy is widely used in the manufacture of various structural parts of aircraft, most of which are joined and assembled through hole structures. However, stress concentration will occur around the hole during the service process of the part, which is easy to cause fatigue failure. It is significant to improve the fatigue performance of the hole structure. In this work, surface strengthening of 7075-T6 aluminum alloy holes induced by split sleeve cold expansion (SCE) was studied regarding surface microstructure, microhardness, and residual stress profiles. The effects of SCE process on the fatigue properties in different stress levels were finally discussed. The results show that the surface of the SCE sample undergoes severe plastic deformation and forms a gradient grain structure with a layer of nanocrystals in the outermost layer. This process lead to an increase of surface microhardness by about 14.3% and a compressive residual stress of up to 255 MPa. Dislocation slip is dominant deformation mechanism in the expansion process. During expansion, more dislocation tangles, dislocation walls and dislocation cells appear, which induces the formation of sub-grain boundaries and refines the grains. In the SCE samples, the high-strength nanocrystals on the surface of holes, the excellent resistance to strain localization of the gradient structure and the high compressive residual stress can effectively hinder the initiation of fatigue cracks and increase the high-cycle fatigue life by 9 times.

Cyclic Extrusion Compression Process for Achieving Ultrafine-Grained 5052 Aluminum Alloy with Eminent Strength and Wear Resistance

Previous studies have yet to show a consistent effect of severe plastic deformation (SPD) processing on the wear behavior of different metals and alloys. To fill this scientific gap, this study investigated the effect of the cyclic extrusion compression (CEC) process, as one of the prominent SPD techniques, on the wear behavior of AA5052. In addition, the microstructure evolution and mechanical properties of the sample before and after the process were experimentally examined and studied. It was found that the yield and ultimate tensile strength of the AA5052 improved significantly after the first pass, while the elongation-to-failure decreased considerably. Further, the subsequent passes mildly changed the trend of increasing strength and reducing elongation-to-failure. SEM morphology indicated that the ductile mode of the initial annealed alloy changed to a combination of ductile and brittle failure modes, in which the level of the brittle failure mode increased with the addition of passes. TEM observations showed that the grain refinement during the CEC process included the formation of dislocation cell structures, subgrain boundaries, and low-angle grain boundaries, with the subgrain boundaries initially evolving into low-angle grain boundaries and, eventually, due to the imposition of additional plastic strain, into high-angle grain boundaries. Furthermore, the CEC process and its increased number of passes led to a significant improvement in wear resistance due to the enhanced tensile strength achieved through grain refinement. In this regard, the wear mechanism of the initial alloy was a combination of adhesion and delamination, with the plastic deformation bands changing to plowing bands with decreased adhesive wear during the process. Eventually, oxidization was found to be a mechanism contributing to wear under all conditions.

A novel ultrasonic consolidation method for rapid preparation of diamond/Cu composites

• An innovative method is proposed to design and manufacture diamond/Cu composites. • Diamond/Cu composites were fabricated via ultrasonic consolidation and resistance fast diffusion process. • The interfacial configuration of diamond/Cu composites was investigated. In this study, diamond/Cu composites were fabricated using ultrasonic consolidation and resistance rapid diffusion technology with Cr addition to improve the wettability between diamond and Cu martix, the interfacial configuration and thermal conductivity of diamond/Cu composites were also investigated. Excellent interfacial bonding between diamond and Cu matrix was achieved by surface metallization of diamond with Cr, and the formation of subgrain boundaries was observed in the Cr 7 C 3 and Cu matrix grains near the interface. The thermal conductivity of the composite prepared by this process reaches 421.314 W/m·K when diamond added mass at 1.34%, which is 12% higher than that of the Cu matrix.

Spheroidization and dynamic recrystallization mechanisms of a novel HIPed P/M superalloy during hot deformation

The spheroidization behavior of γ′ phase and dynamic recrystallization (DRX) mechanisms of a novel HIPed powder metallurgy (P/M) superalloy deformed at high temperatures (1080−1170 ℃) and different strain rates (1–0.001 s−1) are investigated. The results show that the spheroidization behavior of γ' phase and DRX mechanisms are greatly influenced by deformation condition. The coarse γ′Ⅰ phase promotes the DRX process, while the fine spherical γ'Ⅲ phase results in the formation of sub-grain boundaries. Thus, the grains are refined. During hot deformation, some coarse γ′Ⅰ and γ′ⅠⅠ phases transform into the fine spherical γ'Ⅲ phases, while some initial γ'Ⅲ phases gradually diminish. Besides, the spheroidization rates of γ′Ⅰ, γ′Ⅱ and γ'Ⅲ phases increase with the increase of strain rate. The low DRX volume fraction and refined grains with the average size of 2.27 µm are obtained at 1110 ℃/1 s−1. It is attributed to the fact that the DRX nucleation is obviously enhanced and the pinning effects of spherical γ′Ⅲ phases on dislocations accelerate the formation of sub-grains. In addition, the discontinuous DRX is the main DRX mechanism of this novel P/M superalloy.

Enhancing ambient temperature grain boundary plasticity by grain refinement in bulk magnesium

Room temperature ductility of magnesium is known to be dramatically enhanced by partial contribution of grain boundary sliding. However, the effect of grain size on grain boundary plasticity as well as accommodation process for this unique room temperature grain boundary sliding are unclear. In this study, tensile tests at ambient temperatures and detailed deformed microstructural observations are performed to investigate these points using extruded magnesium of average grain sizes between 1 μm and ∼50 μm. The results of tensile tests exhibit that elongation-to-failure in tension and deformation mechanism vary with grain sizes. Fine-grained magnesium (in orders of several micrometer) shows the elongation-to-failure in tension of ∼100% with activation energy of 80 kJ/mol, which is close to grain boundary diffusion of magnesium. This high ductility results from grain boundary sliding accommodated with dislocation slip by diffusion process. Accordingly, the ductility and activation energy reduces with grain size coarsening. Deformed microstructural observations using EBSD and TEM display the activation of non-basal dislocations at grain boundaries. Specific regions in geometrically necessary dislocation map of grain interior consisting of meso- and coarse-structures (>∼10 μm) show a high value, which suggests the presence of strains. Moreover, the formation of sub-grain boundaries is confirmed in grain interior of coarse-grained structure. This is attributed to dominant occurrence of intragranular deformation mode, associated with insufficient diffusivity, such as grain boundary diffusion.

Tension/compression asymmetry of quasi – Static and dynamic mechanical properties in a face centered cubic Ni-W-Co ternary alloy

In this paper a typical tension/compression asymmetry (TCA) behavior of a Ni48W35Co17 alloy is found by quai-static and dynamic mechanical tests and then systematically investigated by in-situ tensile and compression tests equipped with SEM, EBSD, TEM, etc. The true stress obtained by compression of this alloy is found increasing to 2500 MPa or even larger with strain over 0.5, which is almost twice of the value of tension. In tension, a little increase of reinforcement coefficient is found with increasing strain rates, from 0.36 to 0.56 max. In compression, reinforcement coefficient is found increased apparently from 0.76 to 1.24 according to the exponential stress-strain relationship. The TCA behavior of this alloy is related to the dislocation nucleation stress asymmetry. The TCA of yield strength is related to the formation of textures on [111] and [110] directions, since a larger nucleation stress is required in uniaxial compression than tension. TCA is also promoted by the formation of twin boundaries or sub-grain boundaries due to the higher average nucleation stress tilt grain boundaries in compression than intension. TCA behavior of this alloy in dynamic deformation is attributed to the high dislocation densities due to the formation of very thin deformation twins.

Hot compression behaviors and deformation mechanisms of a Ni–Co-based superalloy with columnar grains

In this work, hot compression behaviors and deformation mechanisms of a Ni–Co-based superalloy prepared using directional solidification (DS) were investigated by carrying out the isothermal compression tests within the temperature range of 1080–1190 °C and the strain rate range of 0.001–1 s-1 under the true strain of 0.693. The effects of temperature and strain rate on dynamic recrystallization (DRX) were analyzed, and constitutive equations were established. The activation energies for γ+γʹ dual-phase and the γ single-phase regions of Ni–Co-based superalloy with columnar grains were 1190 kJ mol-1 and 415 kJ mol-1, respectively. The results showed that the dominant deformation mechanisms were closely related to the strain rate and temperature. DRX was accelerated at low strain rate conditions, while the DRX process was apparently sluggish at strain rates higher than 1 s-1. The undissolved γʹ phase interacted with dislocations and accelerated the DRX of the matrix during γʹ sub-solvus temperature (1080–1120 °C) deformation. Continuous dynamic recrystallization (CDRX) nucleation proved to play a dominant role. During γʹ super-solvus temperature (1150–1190 °C) deformation, the dominant dynamic softening mechanism of the alloy is discontinuous dynamic recrystallization (DDRX). Local migration of grain boundaries (GBs) causes an increase of misorientation within the deformed grains and induced the formation of subgrain boundaries near the GBs, which subsequently evolved into high angle grain boundaries (HAGBs) and participated in DDRX. Furthermore, during high-temperature deformation in Ni–Co-based superalloys, the relatively rare microtwins (MTs) were detected under compression at 1100 °C/1 s-1.

Characterization of Structural Defects in (Cd,Zn)Te Crystals Grown by the Travelling Heater Method

Structural defects and compositional uniformity remain the major problems affecting the performance of (Cd, Zn)Te (CZT) based detector devices. Understanding the mechanism of growth and defect formation is therefore fundamental to improving the crystal quality. In this frame, space experiments for the growth of CZT by the Travelling Heater Method (THM) under microgravity are scheduled. A detailed ground-based program was performed to determine experimental parameters and three CZT crystals were grown by the THM. The structural defects, compositional homogeneity and resistivity of these ground-based crystals were investigated. A ZnTe content variation was observed at the growth interface and a high degree of stress associated with extensive dislocation networks was induced, which propagated into the grown crystal region according to the birefringence and X-ray White Beam Topography (XWBT) results. By adjusting the growth parameters, the ZnTe variations and the resulting stress were efficiently reduced. In addition, it was revealed that large inclusions and grain boundaries can generate a high degree of stress, leading to the formation of dislocation slip bands and subgrain boundaries. The dominant defects, including grain boundaries, dislocation networks and cracks in the interior of crystals, led to the resistivity variation in the crystals. The bulk resistivity of the as-grown crystals ranged from 109 Ωcm to 1010 Ωcm.