Alpha-beta(α-β)titanium alloys such as Ti-6Al-4V(wt.%,here-after the same)and Ti-6Al-2Sn-4Zr-2Mo fabricated by fusion-based additive manufacturing(AM)typically exhibit a strong columnar prior-βgrain structure.These...Alpha-beta(α-β)titanium alloys such as Ti-6Al-4V(wt.%,here-after the same)and Ti-6Al-2Sn-4Zr-2Mo fabricated by fusion-based additive manufacturing(AM)typically exhibit a strong columnar prior-βgrain structure.These columnar prior-βgrains with their001along the build direction not only lead to solidification tex-ture but also cause subsequentα-phase textures[1].The forma-tion of theseα-phase textures is a consequence of theβ→αtransformation obeying the Burgers orientation relationship(BOR)[1-5],which results in[0001]of theα-phase being orientated at about either 45°or 0°relative to the horizontal.They affect the deformation behaviour and mechanical properties[1,6].Defined by the BOR,a singleβ-phase grain can bring forth 12α-phase vari-ants[2,7],leading to significant microstructural intricacy.Theseα-phase variants do not form randomly in eachβ-phase grain.Rather,their formation displays specific crystallographic features,known asα-variant selection,which is common in Ti alloys.In an extreme case,α-variant selection can lead to the formation of a singleα-phase crystal through anα→β→αtransformation cy-cle[8,9].展开更多
It has been a central task of solidification research to predict solute microsegregation. Apart from the Lever rule and the Scheil-Gulliver equation, which concern two extreme cases, a long list of microsegregation mo...It has been a central task of solidification research to predict solute microsegregation. Apart from the Lever rule and the Scheil-Gulliver equation, which concern two extreme cases, a long list of microsegregation models has been proposed. However, the use of these models often requires essential experimental input information, e.g., the secondary dendrite arm spacing(λ), cooling rate( ˙T) or actual solidification range(△T). This requirement disables these models for alloy solidification with no measured values for λ,˙T and △T. Furthermore, not all of these required experimental data are easily obtainable. It is therefore highly desirable to have an easy-to-apply predictive model that is independent of experimental input,akin to the Lever rule or Scheil-Gulliver model. Gong, Chen, and co-workers have recently proposed such a model, referred to as the Gong-Chen model, by averaging the solid fractions(f_(s)) of the Lever rule and Scheil-Gulliver model as the actual solid fraction. We provide a systematic assessment of this model versus established solidification microsegregation models and address a latent deficiency of the model, i.e.,it allows the Lever rule solid fraction fsto be greater than one(f_(s)> 1). It is shown that the Gong-Chen model can serve as a generic model for alloy solidification until fsreaches about 0.9, beyond which(f_(s)> 0.9) its applicability is dictated by both the equilibrium solute partition coefcient(k) and the solute diffusion coefcient in the solid(Ds), which has been tabulated in detail.展开更多
A general rule of strength and plasticity was proposed for three typical wrought Al alloys(2xxx,6xxx,and 7xxx)subjected to different aging times.Investigations of the work-hardening processes and dislocation configura...A general rule of strength and plasticity was proposed for three typical wrought Al alloys(2xxx,6xxx,and 7xxx)subjected to different aging times.Investigations of the work-hardening processes and dislocation configurations in tensile and compressive testing reveal that this general rule arises because there is a common mechanism for these three kinds of wrought alloys whereby the tendency for cross-slip increases monotonously with aging time.By analyzing the strain hardening exponent and the stacking fault energy,it is demonstrated that the change in the dislocation slip mode is attributed mainly to the formation of second phases rather than to the matrix composition.Accordingly,a new work-hardening model was proposed for wrought Al alloys containing second phases and this explains the interaction between dislocations and second phases and other relevant experimental phenomena.This work is therefore beneficial for quantitatively investigating and optimizing the strength and plasticity of wrought aluminum alloys.展开更多
The authors are very sorry for their carelessness that there are some problems with Eq.(14)and the fund in the original manuscript.Firstly,Eq.(14)in the original manuscript is:k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(s...The authors are very sorry for their carelessness that there are some problems with Eq.(14)and the fund in the original manuscript.Firstly,Eq.(14)in the original manuscript is:k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp)=η(k s−1)+1,the latter step of Eq.(14)is repeated with Eq.(15),thus it should be deleted and Eq.(14)revised to k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp).展开更多
基金supported by the Australian Research Council (ARC) through DP180103205
文摘Alpha-beta(α-β)titanium alloys such as Ti-6Al-4V(wt.%,here-after the same)and Ti-6Al-2Sn-4Zr-2Mo fabricated by fusion-based additive manufacturing(AM)typically exhibit a strong columnar prior-βgrain structure.These columnar prior-βgrains with their001along the build direction not only lead to solidification tex-ture but also cause subsequentα-phase textures[1].The forma-tion of theseα-phase textures is a consequence of theβ→αtransformation obeying the Burgers orientation relationship(BOR)[1-5],which results in[0001]of theα-phase being orientated at about either 45°or 0°relative to the horizontal.They affect the deformation behaviour and mechanical properties[1,6].Defined by the BOR,a singleβ-phase grain can bring forth 12α-phase vari-ants[2,7],leading to significant microstructural intricacy.Theseα-phase variants do not form randomly in eachβ-phase grain.Rather,their formation displays specific crystallographic features,known asα-variant selection,which is common in Ti alloys.In an extreme case,α-variant selection can lead to the formation of a singleα-phase crystal through anα→β→αtransformation cy-cle[8,9].
基金funding from the Australian Research Council(ARC) via DP180103205。
文摘It has been a central task of solidification research to predict solute microsegregation. Apart from the Lever rule and the Scheil-Gulliver equation, which concern two extreme cases, a long list of microsegregation models has been proposed. However, the use of these models often requires essential experimental input information, e.g., the secondary dendrite arm spacing(λ), cooling rate( ˙T) or actual solidification range(△T). This requirement disables these models for alloy solidification with no measured values for λ,˙T and △T. Furthermore, not all of these required experimental data are easily obtainable. It is therefore highly desirable to have an easy-to-apply predictive model that is independent of experimental input,akin to the Lever rule or Scheil-Gulliver model. Gong, Chen, and co-workers have recently proposed such a model, referred to as the Gong-Chen model, by averaging the solid fractions(f_(s)) of the Lever rule and Scheil-Gulliver model as the actual solid fraction. We provide a systematic assessment of this model versus established solidification microsegregation models and address a latent deficiency of the model, i.e.,it allows the Lever rule solid fraction fsto be greater than one(f_(s)> 1). It is shown that the Gong-Chen model can serve as a generic model for alloy solidification until fsreaches about 0.9, beyond which(f_(s)> 0.9) its applicability is dictated by both the equilibrium solute partition coefcient(k) and the solute diffusion coefcient in the solid(Ds), which has been tabulated in detail.
基金financially supported by the Youth Innovation Promotion Association CAS(Nos.2021192,2018226,51871223,51790482,52130002)the KC Wong Education Foundation(No.GJTD-2020–09)+1 种基金the Chinese Academy of Sciences(Grants 174321KYSB20210002)One of the authors was supported by the European Research Council(No.267464-SPDMETALS(TGL))。
文摘A general rule of strength and plasticity was proposed for three typical wrought Al alloys(2xxx,6xxx,and 7xxx)subjected to different aging times.Investigations of the work-hardening processes and dislocation configurations in tensile and compressive testing reveal that this general rule arises because there is a common mechanism for these three kinds of wrought alloys whereby the tendency for cross-slip increases monotonously with aging time.By analyzing the strain hardening exponent and the stacking fault energy,it is demonstrated that the change in the dislocation slip mode is attributed mainly to the formation of second phases rather than to the matrix composition.Accordingly,a new work-hardening model was proposed for wrought Al alloys containing second phases and this explains the interaction between dislocations and second phases and other relevant experimental phenomena.This work is therefore beneficial for quantitatively investigating and optimizing the strength and plasticity of wrought aluminum alloys.
基金supported by the Youth Innovation Promotion Association CAS(Grant No.202,1192)the National Natural Science Foundation of China(NSFC)(Nos.51,871,223,51,790,482,52,130,002)+2 种基金the KC Wong Education Foundation(No.GJTD-2020-09)the Chinese Academy of Sciences(Grants 174321KYSB20210002)supported by the European Research Council(No.267,464-SPDMETALS(TGL))。
文摘The authors are very sorry for their carelessness that there are some problems with Eq.(14)and the fund in the original manuscript.Firstly,Eq.(14)in the original manuscript is:k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp)=η(k s−1)+1,the latter step of Eq.(14)is repeated with Eq.(15),thus it should be deleted and Eq.(14)revised to k=k_(s)f^(O)_(sp)/f_(sp)+f^(C)_(sp)/f_(sp).
