Relationship among Mechanical Properties Anisotropy,Microstructure and Texture in AA 6111 Alloy Sheets

We comparatively studied the mechanical properties anisotropy, microstructure and texture of the commercial and the new developed AA6111 alloys through tensile test, optical microscopy, and XRD analysis. The results show that the anisotropy of mechanical properties for the developed AA6111 alloy is lower than that of the commercial alloy. The developed alloy possesses higher r value, lower Ar value and more uniform microstructure, compared with the commercial AA6111 alloy, indicating that the deep drawability of the developed alloy has been improved significantly. The recrystallization textures of the two alloy sheets are also different. The recrystallization texture of the commercial alloy sheet mainly includes Cube and { 114}〈311〉 orientations, while the recrystallization texture of developed alloy sheet consists of Cube, Goss and R orientations. The relationships among the deep drawabilities, microstructure and texture were discussed thereafter.

Simultaneous enhancement of mechanical properties and corrosion resistance of as-cast Mg-5Zn via microstructural modification by friction stir processing

Magnesium alloys are ideal lightweight materials;however,their applications are extremely limited due to their low strength,poor ductility,and weak corrosion resistance.In the present study,a friction stir processing(FSP)treatment was employed to optimize the mechanical properties and corrosion resistance of an as-cast Mg-5Zn alloy.The average grain size of the Mg-5Zn alloy was refined from 133.8μm to1.3μm as a result of FSP.Along different directions,FSP exhibited the enhancement effects on different mechanical properties.Furthermore,according to the potentiodynamic polarization results,the corrosion current density at the free-corrosion potential of the FSPed sample,was 4.1×10^(-6)A/cm^(2)in 3.5 wt.%Na Cl aqueous solution,which was significantly lower than that of the as-cast sample.Electrochemical impedance spectroscopy revealed that the polarization impedance,Rp,of the FSPed sample was 1534Ω/cm^(2)in 3.5 wt.%NaCl aqueous solution,which was 71.4%greater than that of the as-cast sample.The corrosion morphology of the FSPed sample in 3.5 wt.%NaCl aqueous solution exhibited largely uniform corrosion,rather than severe localized corrosion characteristics,which further reduced the corrosion depth on the basis of reducing the corrosion current density.The results presented herein indicate that FSP is a viable technique for simultaneously improving the mechanical properties and corrosion resistance of the as-cast Mg-5Zn alloy.

Analysis of anisotropy mechanism in the mechanical property of titanium alloy tube formed through hot flow forming

Anisotropy of mechanical property is an important feature influencing the service performance of titanium(Ti)alloy tube component.In this work,it is found that the hot flow formed Ti alloy tube exhibits higher yield strength along circumferential direction(CD),and larger elongation along rolling direction(RD),presenting significant anisotropy.Subsequently,the quantitative characteristics and underlying mechanism of the property anisotropy were revealed by analyzing the slip,damage and fracture behavior under the combined effects of the spun{0002}basal texture and fibrous microstructure for different loading directions.The results showed that the prismatic slip in primaryαgrain is the dominant deformation mechanism for both loading directions at the yielding stage.The prismatic slip is harder under CD loading,which makes CD loading present higher yield strength than RD loading.Additionally,the yield anisotropy can be quantified through the inverse ratio of the averaged Schmid Factor of the activated prismatic slip under different loading directions.As for the plasticity anisotropy,the harder and slower slip development under CD loading causes that the CD loading presents larger external force and normal stress on slip plane,thus leading to more significant cleavage fracture than RD loading.Moreover,the micro-crack path under RD loading is more tortuous than CD loading because the fibrous microstructure is elongated along RD,which may suppress the macro fracture under RD loading.These results suggest that weakening the texture and fibrous morphology of microstructure is critical to reduce the differences in slip,damage and fracture behavior along different directions,alleviate the property anisotropy and optimize the service performance of Ti alloy tube formed by hot flow forming.

Insight into the formation mechanism and interaction of matrix/TiB whisker textures and their synergistic effect on property anisotropy in titanium matrix composites

Considerable studies on processed pure titanium and titanium alloys have proved the possibility of prop-erty anisotropy induced by crystallographic textures,but limited information is available for the intrinsic coupling of matrix and reinforcement textures and their synergistic effect on property anisotropy in tita-nium matrix composite(TMCs).In the present work,an advanced EBSD/EDS coupling method was used to investigate the formation mechanism of primaryαand secondaryαtextures in the matrix alloy.It is revealed for the first time that the reinforcement TiB_(w)displays a{100}<010>texture after hot rolling and has little effect on the matrix texture component but weakens texture intensity.Significant anisotropies in the tensile strength and ductility can be all noted at room and high-temperatures,which is the syn-ergistic effect of the matrix texture and the aligned TiB_(w).The mean Schmid factor of each slip system was calculated to evaluate the influence of matrix texture on the minimum active stress of slip deforma-tion in the different tensile directions.The analysis shows that the strong T-type matrix texture results in higher strength but lower ductility when loaded in the transverse direction.Moreover,a generalized shear-lag model was modified to quantitatively evaluate the strengthening contribution of aligned TiB_(w),which decreases with increasing off-axis angle and test temperature.A new parameter,defined as the critical aspect ratio of the off-axis whisker,was proposed to rationalize why the TiB_(w) failure mechanism converts from TiB_(w) fracture to TiB_(w)/matrix interfacial debonding with increasing off-axis angle and test temperature.

High Temperature Stress Rupture Anisotropy of a Ni-Based Single Crystal Superalloy

High temperature stress rupture anisotropies of a second generation Ni-base single crystal（SC） superalloy specimens with [001], [011] and [111] orientations under 900 ℃/445 MPa and 1100 ℃/100 MPa have been investigated in the present study, with attentions to the evolution of γ/γ′ microstructure observed by scanning electron microscopy and the dislocation configuration characterized by transmission electron microscopy in each oriented specimen. At 1100 ℃/100 MPa as well as 900 ℃/445 MPa, the single crystal superalloy exhibits obvious stress rupture anisotropic behavior. The [001] oriented specimen has the longest rupture lifetime at 900 ℃/445 MPa, and the [111] oriented sample shows the best rupture strength at 1100 ℃/100 MPa. While the [011] oriented specimen presents the worst rupture lifetime at each testing condition, its stress rupture property at 1100 ℃/100 MPa is clearly improved, compared with900 ℃/445 MPa. The evident stress rupture anisotropy at 900 ℃/445 MPa is mainly attributed to the distinctive movement way of dislocations in each oriented sample. Whereas, at 1100 ℃/100 MPa, together with the individual dislocation configuration, the evolution of γ/γ′ microstructure in each orientation also plays a key role in the apparent stress rupture anisotropy.