Low Boundaries Research Articles

DenMap single crystal solidification structure feature extraction: Automation and application

A fully automatic, standardised, and validated dendritic core detection algorithm, DenMap, is applied to analyse CMSX-4® and CMSX-10® single crystal microstructure. Through the utilisation of novel imaging techniques such as Gaussian deconvolution and minimisation-based thresholding, the newly enhanced version of DenMap demonstrates a significant improvement in detection accuracy and range of applications. The results indicate dendrites preferentially form channels, with array disorder increasing with height from the chill plate. A new twisting phenomenon has been observed that may have significant impact on the development of low and high angle grain boundaries and porosity formation within the microstructure. DenMap provides the foundation for 3D reconstruction methodologies and advanced pattern recognition techniques. This new standardised approach will facilitate the development of machine learning algorithms and eventually AI for single crystal solidification studies, particularly for the purpose of process optimisation.

Comparison of K-doped and pure cold-rolled tungsten sheets: Tensile properties and brittle-to-ductile transition temperatures

For high-temperature environments, as in future fusion reactors, the use of tungsten materials has been sincerely discussed in the last decade. Although severe cold-rolling of tungsten leads to significant improvements in mechanical properties, the fine-grained microstructure of such tungsten material has to be stabilized. For that, the use of potassium-doping (K-doping) in tungsten sheets is investigated in our ongoing study. In this work, we compare mechanical properties of warm- and cold-rolled sheets of pure tungsten and K-doped tungsten (for five different degree of deformation respectively) by means of fracture toughness tests and tensile tests.Fracture toughness and brittle-to-ductile transition temperatures (TBDT) are assessed, showing a slightly lower transition temperature for the cold-rolled K-doped sheets (lower than −100 °C for the 50 µm thick foil). The better performance of the K-doped sheet is related to its finer grain size. The thickest K-doped sheet shows a much higher TBDT than its pure tungsten counterpart. This is presumably caused by the presence of several tens of micrometre thick bands, containing only low angle boundaries, in the microstructure of the K-doped sheet.Tensile tests reveal an outstanding yield strength of 2860 MPa and an ultimate tensile strength of 2970 MPa for the thinnest K-doped sheet with similar, but slightly lower values for the pure tungsten counterpart. Both thinnest sheets show a drastic increase in ultimate tensile strength in correlation to their mean grain size, much higher than expected by a Hall-Petch relation. This deviation has been observed for the microhardness as well and is assumed to be caused by an extraordinary increase in the density of dislocations.Our results indicate that no disadvantages in tensile strength and brittle-to-ductile transition are to be expected compared to pure tungsten, when K-doped tungsten is used to inhibit recrystallization in high-temperature environments.

Tailoring twist extrusion process; the better strain behavior at the lower required loads

This study dealt with discovering the optimal conditions of the twist extrusion parameters for producing materials possess enhanced strain behavior with the least amount of extrusion load. It was found that the twist angle has a dominant influence on the strain behavior of the deformed sample with the contribution percentage of 56%, while the effect of friction coefficient would be the most noticeable if the required extrusion load is considered. Based on above, pure copper with the square cross-section was subjected to the process with the large twist angle at the best lubricant state. The results showed that the strength and hardness of the deformed copper were considerably enhanced compared to the initial condition due to the substantial grain refinement. The uniform plastic deformation zone of the deformed sample is limited which causes the reduction of strain-hardening exponent and ductility. Moreover, the lateral region of the sample’s cross-section endures larger plastic strain compared to the central one, leading to owning higher hardness. A combined microstructure consisting of low angle dislocation walls and high angle grain boundaries was also determined for the deformed copper.

EBSD Study of Delta-Processed Ni-Based Superalloy

Nickel-based superalloys are extensively used in the aerospace and power generation industries due to their excellent mechanical properties at elevated temperatures and good corrosion resistance. Typically, these alloys require accomplishing critical standards during their manufacturing process. In this study, an Inconel 718 (IN718) Ni-based superalloy was subjected to a delta-processing treatment (DP718) and subsequently deformed at high temperature. Samples were compressed below and above the δ-solvus temperature at two different strain rates of 0.001 s−1 and 0.01 s−1. A detailed microstructural characterization was carried out by the electron backscattered diffraction technique (EBSD). Kikuchi patterns and the orientation relationship of the δ-phase were identified. For samples deformed above the δ-solvus at 0.01 s−1, an increase in the percentage of low angle grain boundaries (LAGB) within deformed grains and a decrease in high angle grain boundaries (HAGB) were observed. Comprehensive observation of the microstructural evolution of IN718 subjected to DP718 using orientation map images was also performed.

Guanidinium iodide modification enabled highly efficient and stable all-inorganic CsPbBr3 perovskite solar cells

The preparation of high-quality perovskite thin films with low grain boundaries and defect states plays an important role in determining the photovoltaic performance and stability of perovskite solar cells (PSCs). It has been proved that the inorganic CsPbBr3 perovskite material has unique stability. However, the wide band gap and small light absorption range limit the power conversion efficiency (PCE) of the corresponding devices. Here, we report that the addition of guanidine iodide (GAI) into CsPbBr3 precursor solution can greatly improve the quality of CsPbBr3 film, leading to inhibition of interfacial recombination, promotion of charge migration and reduction of trap state density. Ultimately, the planar PSC with GAI modified CsPbBr3 film yields a champion efficiency of 8.54%, much higher than the control one (6.56%).

Microstructure and enhanced mechanical properties of hybrid-sized B4C particle-reinforced 6061Al matrix composites

In the present work, the microstructure and elevated-temperature tensile properties of 6061Al alloy and 6061 Al matrix composites reinforced with bimodal-sized (micron + nano) B4C particles or monomodal micro-sized B4C particles are investigated. The results demonstrate that nanoscale B4C (n-B4C) particles are present both at the grain boundaries and within the grains in the composite. Due to the presence of n-B4C particles, there is a decrease in matrix grain size and recrystallization region percentage, and an increase in proportion of low angle grain boundaries. The combined mechanical property and theoretical analyses reveal that n-B4C particles play a significant role in hindering the dislocation movement and limiting the grain boundary slip during tensile deformation, causing an increase in ultimate tensile strength of the annealed composite with bimodal-sized B4C particles at elevated temperatures. The analysis shows that dislocation glide and climb are responsible for the elevated-temperature strengthening mechanism associated with the n-B4C particle addition. For the annealed composites, the ductile fracture of matrix is the primary failure mode at elevated temperatures.

Effect of Deformation on Precipitation and the Microstructure Evolution during Multistep Thermomechanical Processing of Al-Zn-Mg-Cu Alloy

In order to obtain fine grained structure efficiently, a new multi-step rolling process (MSR: pre-deformation + intermediate annealing + hot deformation) was applied in Al-Zn-Mg-Cu plates. Conventional hot rolling (CHR) was also carried out as a contrast experiment. The evolution of microstructures and improvement of mechanical properties were analyzed by optical microscope, scanning electron microscope, transmission electron microscope, X-ray diffractometer, and tensile tests. The results show that the MSR process can obtain finer longitudinal grain size and better mechanical properties than CHR, which can be explained as follows: spheroidization of precipitates wrapped by high density dislocations could be promoted by increased pre-deformation; numerous ordered substructures were formed during short-period intermediate annealing at high temperature; in the subsequent hot rolling process, the retained spherical precipitates pinned dislocations and boundaries. With the increase of accumulated strain, low angle grain boundaries gradually transformed into high angle grain boundaries, leading to grain refinement. With the increased pre-deformation (MSR1 20 + 60%, MSR2 40 + 40%, MSR3 60 + 20%), the effect of grain refinement and plasticity improvement gradually weakened. The optimum thermomechanical process (MSR1 solid solution + pre-deformation (300 °C/20%) + intermediate annealing (430 °C/5 min) + hot deformation (400 °C/60%)) was obtained, which can increase elongation by ~25% compared with the CHR process, while maintaining similar high strength for reduced longitudinal grain size.

Role of bainitic microstructures with M-A constituent on the toughness of an HSLA steel for seismic resistant structural applications

Fracture toughness of the coarse-grained heat-affected zone (CGHAZ) of fusion welded HSLA steel is severely reduced at low temperatures with the combination of deleterious microstructures such as bainitic ferrite (BF), granular bainite (GB), polygonal ferrite (PF), and the martensite-austenite (M-A) constituents. Toughness is one of the basic requirements for seismic resistant steels. The three heat input conditions (different cooling rate) were thermo-mechanically simulated, and the combined effect of M-A constituents with bainitic microstructures on toughness was examined. As the heat input changes from low to high, a combination of acicular ferrite (AF) and BF microstructures changes to a combination of PF, GB and M-A constituent. The former microstructure combination provides better toughness (ductile), whereas the latter makes the samples more brittle. The coarse BF, GB, and PF microstructures with low angle grain boundaries (LAGBs) make them brittle by easy crack propagation. Moreover, harder microstructures such as M-A can potentially act as cleavage initiation sites. However, a high frequency of high angle grain boundaries (HAGBs) in the AF microstructure can suppress the crack propagation, which turns the fracture to completely ductile. Also, it is observed that the M-A constituent in CGHAZ was abundant in martensite rather than the austenite.

Investigation on micromechanism involved in ferrite hardening after prestraining of dual-phase steel

The evolution of low angle grain boundaries (LAGBs) and Taylor factor (TF) was investigated by EBSD analysis to reveal the micromechanism of ferrite hardening for dual-phase steel during prestraining from 1% to 5%. The results showed plastic deformation was dominated by soft ferrite phases during prestraining from 1% to 3%, and subsequently, transformed to interface deformation during prestraining from 3% to 5%. Due to the evolution of LAGBs, dislocation substructures were generated during prestraining. The fraction of soft grains within the range of TF~2–3 gradually decreased after the hardening, indicating the slip system was more difficult to be activated within ferrite. The hardening of ferrite was attributed to the formation of stable dislocation subgrain structures and the hardening of grain orientation as well. When the prestraining degree went above 3%, the ferrite phases can be completely hardened. After ferrite hardening, the strain hardening ability of the dual-phase steel was reduced, the yield strength was increased and the uniform elongation was decreased at the same time. It was noteworthy that the stress drop (up to 10 MPa) occurred on the stress-strain curve after the completion of strain hardening, and the plastic deformation was initiated directly at interface, exhibiting a mixed mode of failure involving both cleavage brittle and dimple ductile fracture. This work is aiming to provide detailed insights and experimental evidence for ferrite hardening behaviour after prestraining, which is expected to make great contribution for better service protection of the pipeline using dual-phase steel.

Vacuum superplastic deformation behavior of a near-α titanium alloy TA32 sheet

The superplastic deformation and microstructure characterization of a near α titanium alloy TA32 sheet with a nominal composition of Ti-5.5Al-3.5Sn–3Zr–1Mo-0.5Nb-0.7Ta-0.3Si in vacuum environment were systematically investigated. The maximum superplastic elongation was obtained to be 702% at 940 °C with a strain rate of 3.33 × 10-3 s-1. The superplastic deformation constitutive equation was established and the average apparent activation energy (Q) and strain rate sensitivity (m) were calculated to be 316.3 kJ/mol and 0.46, respectively. The spheroidizing process of α lath was accelerated by dynamic globularization (DG). Active dislocation motion was observed and developed an attractive interaction with Silicides ((TiZr)6Si3). Transformation of low angle grain boundaries (LAGBs,2° < θ < 15°) to high angle boundaries (HAGBs, θ > 15°) was promoted by dynamic recrystallization (DRX). Significant change in texture intensity of B-type and R-type texture was observed after superplastic deformation, which was attributed to grain rotation. Superplastic deformation of TA32 sheet was mainly controlled by grain boundary sliding (GBS) along with kinds of accommodation processes, including DG, DRX, dislocation motion, grain rotation and grain growth.

Importancia de los estilos de socialización parental en los roles del acoso entre pares

The family is a primary scenario when studying harassment among equals. Particularly, the parent-child relationship has built up importance in scientific investigations regarding this topic. In this regard, parental socialization may be key as a protection or risk aspect in the occurrence of harassment situations. The development of this study focuses in the achievement of two main objectives. The first objective is aimed to identifying differences in the strategies of parental socialization in both parents, in accordance to the role of the participants involved in harassing behavior. The second objective is based in stablishing if the roles adopted by students have any co-relation with the parental socialization style. In order to fulfill these objectives an empirical, comparative, investigation took place that was based in the design of natural groups, which facilitates the comparison of different variables in social groups that belong to a same culture, e.g. students, where the analyzed variables source differences among individuals. The study had a base of 551 students (290 male and 261 female) from four different educational institutions, with ages ranging from 12 to 18 (µ = 15.2, of = 1.3). Harassment conducts were evaluated in accordance to the Defensor del Pueblo questionnaire, from a version adjusted to the Colombian context. Whereas the parental style of socialization was evaluated in accordance with Escala de Estilos de Socialización Parental en la Adolescencia (ESPA-29) . The participant-type descriptive evaluation highlights that 296 (53.8 %) of the students take part as bully-victims, 95 (17.2 %) take part as non-involved, 87 (15.8 %) take part as victims, and 73 (13.2 %) take part as bullies. These roles were embraced similarly in men and women without a significant relationship between gender and the type of participant ( χ 2 = 5.328, p = .149 &gt; .05). Concerning to the socialization strategies of parental figures, in the mother’s case, the obtained data indicates that the main differences are found in the group of students who embrace the role of offender-victims. In this group, participants show a higher level of i ndifference that non-involved ( p = .023 &lt; .05) and bullies ( p = .007 &lt; .05), a higher level of physical coercion than non-involved ( p = .000 &lt; .05) and victims ( p = .023 &lt; .05), as well as a higher level of the strictness/imposition axis than non-involved ( p = .001 &lt; .05). The latest show higher verbal coercion ( p = .009 &lt; .05) and strictness/imposition ( p = .032 &lt; .05) than bullies. In the father’s case, the obtained data also highlights the bully-victims as the group with higher ennui than non-involved ( p = .000 &lt; .05) and bullies ( p = .046 &lt; .05), higher indifference than non-involved ( p = .000 &lt; .05) and bullies ( p = .010 &lt; .05), higher physical coercion than non-involved ( p = .000 &lt; .05) and victims ( p = .021 &lt; .05), as well as a higher number than non-involved ( p = .001 &lt; .05) in the strictness/imposition axis. The most common parental style strategy in mothers is indulgent (n = 240, 43.6 %), followed by authoritative (n = 161, 29.2 %), neglectful (n = 102, 18.5 %) and last authoritarian (n = 48, 8.7 %). Meanwhile, the indulgent style is also the most common among fathers (n = 211, 38.3 %), followed by neglectful (n = 171, 31 %), authoritative (n = 109, 19.8 %) and authoritarian (n = 60, 10.9 %). This discards the existence of a significant association between the mother’s socialization style and student’s harassment roles. On the other hand, the indulgent style in fathers was significant in relation to the witnesses (χ 2 = 16.88, p = .000 &gt; .001; ϖ = .18, 1-β = .97) and the bully-victims (χ 2 = 8.96, p = .03 &gt; .05; ϖ = .14, 1-β = .80). The parenthood focused on fulfilling the children demands with low boundaries delimitation is reiterative in parents where indulgent is their most common style of parent socialization, which seems to be associated with an expectation to harass. This work highlights the important role that the parent figures play in the formation of psychosocial skills to the integration of children and teenagers. Furthermore, it features the importance of how parents build bonding relationships with their children.

Microstructure Evolution and Tempering Transformation Kinetics in a Secondary Hardened M50 Steel Subjected to Cold Ring Rolling

The microstructure evolution and tempering transformation kinetics of the M50 steel subjected to cold ring rolling (CRR) have been investigated. The results indicate that the brass R{110}<110> texture is weakened with the enhancement of the <111>//ND texture during CRR. Due to the increased low angle boundaries by CRR, the Ac1 temperature decreases while the carbon content and volume fraction of RA increase. During tempering, the activation energy of carbon atoms segregation and transition carbide precipitation decrease, while the activation energy of retained austenite (RA) decomposition increases after CRR. The kinetic analysis shows that the CRR is beneficial to the carbon atoms segregation during the beginning of tempering. Then, the CRR leads to the delay of the onset of transition carbide precipitation, but decreases the whole reaction time, which has been verified by the transmission electron microscopy (TEM) and hardness results. The lagging of transition carbide precipitation in the early stage is caused by the increased segregation trapping of carbon atoms, while the higher nucleation rate is responsible for the enhanced precipitation of transition carbide during the later stage. For the cementite formation, there are no significant changes in the predictive kinetics after the applied CRR. However, the kinetic transformation of RA decomposition is inhibited by the CRR, which is attributed to the higher carbon content and smaller grain size of RA. Additionally, the alloy carbides precipitation is also enhanced by the CRR process during secondary hardening.

Improvement of Mechanical Properties of Multiple Surface Rolled Pure Copper

High strength can be achieved by severe plastic deformation but at the cost of ductility. A novel strategy, which named multiple surface rolling was applied on a homogeneous annealed pure copper to break the strength and ductility trade-off. A combination of high strength and acceptable ductility was achieved in copper strips after submitted to multiple surface rolling. The detail microstructure evolution rolled samples were characterized by EBSD observation and compared with the initially annealed ones. The average grain size does not show significant deviation in both initially annealed and multiple surfaces rolled copper. Detailed observations show a heterogeneous distribution of low angle grain boundaries through thickness direction. The low angle grain boundaries and misorientations revealed the potential strengthening mechanisms in the material. Both microstructural characterization and numerical simulations indicate that multiple surface rolling contributes to strain hardening at the sample surface, while the interior layer was undergoing elastic deformation or partial plastic deformation. This heterogeneous deformation renders copper sheet with a combination of high strength and ductility.

Effect of retrogression re-aging treatment on corrosion behavior of 7055 Al-Zn-Mg alloy

The effect of retrogression re-aging treatment (RRA) on the corrosion behavior of 7055 Al-Zn-Mg alloy was studied in this paper. Results provided that corrosion resistance could be greatly improved by RRA. After the RRA treatment, the isolated precipitates occurred on grain boundaries (GBs) and the low angle grain boundaries (LAGBs) presented a larger fraction compared to that of single-stage peaking aging treatment. The samples after RRA treatment also show better corrosion resistance than that of single-stage peak aging treatment. In addition, of the electrochemical impedance spectroscopy (EIS) analysis showed that the impedance spectrum was consisted of semi-infinite layer diffusion impedance and stagnant Weber impedance. The semi-infinite layer diffusion impedance corresponded to a limited retention layer on the electrode surface while the Weber impedance represented a stagnant layer of corrosion products generated by the anode branches. The aluminum alloy after RRA treatment achieved higher Rf and low Cf, Cp values and its corrosion current density was ten times smaller compared to the single-stage peak aging samples with the 10% hardness losing.

Microstructural evolution and mechanical properties of friction stir welded 12Cr-ODS steel

Abstract 12Cr oxide dispersion strengthened (ODS) steel was welded by friction stir welding (FSW) method. The weld joint is composed of heat-affected zone (HAZ), advancing side thermo-mechanically affected zone (AS-TMAZ), retreating side thermo-mechanically affected zone (RS-TMAZ) and stir zone (SZ). Electron back scattering diffraction (EBSD) results reveal that dynamic recrystallization occurs in SZ and AS-TMAZ, and the size and orientation of the grains change drastically compared with base mental (BM). Structures transfer from elongated grains in BM towards equiaxed grains in SZ. The dynamic recrystallization process is accompanied by a transition from low angle boundaries (LAB) to high angle boundaries (HAB). In SZ, parts of oxide particles are found to agglomerate together. High compressive stress exists in all the FSW joint region, and two peaks are detected in AS-TMAZ and RS-TMAZ, respectively. Compared with the hardness of BM (295 HV), the hardness of SZ increases obviously, and the highest value is up to 350 HV.

Effect of carbon nanotube incorporation on texture evolution and grain boundary constitution in NiCo coatings

Corrosion response of NiCo-carbon nanotube (CNT) composite coatings is extremely sensitive to the CNT content and an optimum CNT amount yields highest corrosion resistance performance. Here, electron back scatter diffraction (EBSD) technique was employed to correlate the microstructure and corrosion behaviour of Ni–Co and NiCo-CNT composite coatings. Texture and grain boundary character distribution (GBCD) analysis revealed that for coating with the “optimum” CNT amount, factors like {111} orientation texture along [100] direction, high density of geometrically necessary dislocations (GNDs), high fraction of low angle grain boundaries (LAGBs) and Σ3 coincidence site lattice (CSLs) (coherent twins) are responsible for decelerated corrosion rate. Whereas, in pristine NiCo coating and NiCo coatings with high CNT content both of which show significantly higher corrosion rates, high energy orientation texture and high fraction of high energy grain boundaries like Σ3 CSLs (incoherent twins), asymmetrical tilt boundaries and high angle grain boundaries HAGBs increased corrosion rate.

Deformation and fracture behavior of the novel NiAl alloy sheet with bimodal laminated structure by in-situ reaction synthesis

Due to the intrinsic brittleness of NiAl alloy, its sheets are difficult to fabricate with traditional casting and rolling methods. To solve this problem, a novel NiAl alloy sheet with a special bimodal laminated structure was successfully designed and fabricated via the in-situ solid-state reaction synthesis using pure Ni and Al foils. The mechanical properties of the bimodal laminated NiAl alloy sheet were tested by hot tensile tests at temperatures ranging from 850 °C to 1000 °C and strain rates ranging from 0.01/s to 0.0005/s. To clarify the deformation mechanism, the deformation microstructure was characterized by scanning electron microscopy and electron backscatter diffraction technology. The fracture behavior was characterized by a three dimensional X-ray microscope. It was found that the sheet with the bimodal laminated structure composed of overlapped coarse-grained layers (CGLs) and fine-grained layers (FGLs) exhibits a significant deformation incompatibility between CGLs and FGLs, leading to a special deformation and fracture behavior. During hot deformation, dislocations mainly accommodate in FGLs at the beginning, and the coarse grains then begin to play a major role in replacing the privilege of FGLs and vital in storing dislocations during further deformation. The bimodal laminated grains are broken up into many fragments and the average grain sizes are refined after deformation due to the transformation of low angle boundaries into high angle boundaries. The nucleation of dynamic recrystallization grains preferentially takes place in FGLs, and DRX will occur in CGLs when sufficient strain and storage energy are accumulated. The fracture surface demonstrates a jagged fracture pattern parallel to the loading direction, which results from the special laminated grain structure. The fracture morphology along the thickness direction experiences dramatic changes related to the non-uniform strain distribution, which presented as the density and size distribution of voids in 3D space. The study is vital to guiding the high temperature forming and service performance of NiAl alloy.

Effects of finish rolling deformation on hydrogen-induced cracking and hydrogen-induced ductility loss of high-vanadium TMCP X80 pipeline steel

An optimum finish rolling deformation (FRD) of thermomechanical controlled processing (TMCP) is suggested to improve the hydrogen-induced ductility loss of high-vanadium X80 pipeline steel in this study. The results demonstrate that with increasing FRD the microstructure refines, the grain size of the steel decreases and the recrystallization degree deepens. The increase of FRD leads to the reduction of low angle grain boundaries (LAGBs) and the grains oriented with plane {100} parallel to normal direction ({100}//ND) fibres, which plays a significant role in improving the resistance of crack propagation. Besides, the differences of effective hydrogen diffusion coefficient and diffusible hydrogen concentration are negligible among four experimental steels with various FRD. However, the best hydrogen-induced ductility loss resistance is obtained in the steel with 40% FRD containing the most nano-scale precipitates acting as effective hydrogen traps.

Contribution of grain boundary misorientation to intragranular globular austenite reversion and resultant in grain refinement in a high-strength low-alloy steel

This paper elucidates the determining role of grain boundary types/misorientations on formation of intragranular globular austenite, which has random orientation or large deviation from the parent austenite, in a high-strength low-alloy bainitic steel during reaustenitization. Results revealed that within the parent austenite with lath bainite, reverted austenite with random orientation or large deviation from the parent austenite can nucleate at the packet and block boundaries with high misorientations, and rapidly evolve to become globular austenite with increase of temperature, making a significant contribution in final austenite grain refinement. While in granular bainite, the low misoriented boundaries belonging to the same Bain group are the preferred nucleation sites for the reverted austenite, which is detrimental to the formation of intragranular globular austenite. In addition, the precipitation mode of cementite is different in the reverse process, that is, cementite is precipitated from the matrix of lath bainite, but it is precipitated from retained austenite or martensite/austenite (M/A) particles in granular bainite, which will also lead to the different or consistent variant orientation of reverted austenite and matrix. Therefore, the final austenite grain refinement in initial granular bainite was mainly due to the formation of intergranular globular reverted austenite, and the refining effect is much lower than that of lath bainite.

Role of Al addition in modifying microstructure and mechanical properties of Mg-1.0 wt% Ca based alloys

In this work, the role of Al addition in modifying the microstructure and mechanical properties of the Mg-1.0Ca-xAl (x = 0.6, 1.0 wt%; termed as XA10 and XA11, respectively) based alloys has been systematically investigated. Microstructural examination showed that, when the Al content is low, the Al and Ca atoms were inclined to segregate to the dislocation lines in the XA10 sample. As a result, the mobility of dislocation was restrained and the dynamic recovery behavior was hindered, which leads to a low degree of dynamic recrystallization. When the Al content is high, in contrast, no apparent Ca/Al segregations along dislocations have been found in XA11-0 extrusion billet during the whole stages of processing, which results in the enhanced dislocation mobility. Consequently, the recovery of dislocations and dynamic recrystallization rate can be largely enhanced at the earlier stage of extrusion. More importantly, subsequently formed high density Guinier-Preston (G.P.) zones and nano-disk Al2Ca phases in the high-Al content Mg sample can play an effective role in inhibiting the growth of subgrains and dynamically recrystallized (DRXed) grains, which enhance the thermal stability of high density low angular grain boundaries (LAGBs) in the later extrusion stage. The high density nano-disk phases, high volume fraction of DRXed grains, as well as the high density LAGBs in the un-DRXed grains, can together contribute to both high strength and good elongation of the XA11 sample. The findings lead to the controllable Mg-Ca based alloy designing strategy that can improve the strength and ductility simultaneously.