This work explores the correlation between the characteristics of the cast structure(dendrite growth pattern,dendrite morphology and macro-texture)and strain hardening capacity during high temperature deformation of M...This work explores the correlation between the characteristics of the cast structure(dendrite growth pattern,dendrite morphology and macro-texture)and strain hardening capacity during high temperature deformation of Mg-5Sn-0.3Li-0 and 3Zn multi-component alloys.The three dimensional(3D)morphology of the dendrite structure demonstrates the transition of the growth directions from<1123>,<1120>and<1122>to<1123>and<1120>due to the addition of Zn.The simultaneous effects of growing tendency and the decrement of dendrite coarsening rate at the solidification interval lead to dendrite morphology transition from the globular-like to the hyper-branch structure.This morphology transition results in the variation of the solidification macro-texture,which has effectively influenced the dominant deformation mechanisms(slip/twin activity).The higher activity of the slip systems increases the tendency of the dendrite arms for bending along the deformation direction and fragmentation.Apart from this,the dendrite holding hyper-branch structure with an average thickness below 20μm are more favorable for fragmentation.The dendrite fragmentation leads to considerable softening fractions,and as an effective strain compensation mechanism increases the workability of dendritic structure.展开更多
The super-austenitic stainless steels are extensively utilized in the seamless tubes production for oil extraction industries. Due to the importance of thermo-mechanical processing in the production of these tubes, th...The super-austenitic stainless steels are extensively utilized in the seamless tubes production for oil extraction industries. Due to the importance of thermo-mechanical processing in the production of these tubes, the dynamic recrystallization （DRX） characteristics of a Cr-Ni super austenitic stainless steel （1.4563） were investigated in the present study. This was performed using the hot compression testing method in the temperature range of 950-1150℃ and the strain rate of 10^-3-10^-1 s^-1. The initiation and evolution of DRX were examined through microstructural analysis. The results indicated that the recrystallized grain formed a necklace type structure at the prior austenite grain boundaries at higher strain rates. In addition, DRX nucleation occurs by bulging and successive strain induced boundary migration （SIBM）.展开更多
Taguchi experimental design technique was applied to determine the most influential controlling parameters of FSP such as tool rotational speed,travel speed,tilt angle and penetration depth on hardness value of Mg.In ...Taguchi experimental design technique was applied to determine the most influential controlling parameters of FSP such as tool rotational speed,travel speed,tilt angle and penetration depth on hardness value of Mg.In this case,9 combinations of these 4 essential processing parameters were set and Taguchi's method followed exactly.Signal to noise ratio(S/N)analysis showed that maximum hardness achieved when rotational and travel speeds,penetration depth and tilt angel were chosen as 1600 rpm,63 mm/min,0.1 mm and 2°,respectively.In addition,analysis of variance(ANOVA)technique indicated that tilt angle and rotational as well as travel speed are the significant influential parameters in the hardness value of the treated samples,respectively.Finally a model for hardness values based on FSP parameters was calculated by design expert which was also confirmed by experimental results.展开更多
文摘This work explores the correlation between the characteristics of the cast structure(dendrite growth pattern,dendrite morphology and macro-texture)and strain hardening capacity during high temperature deformation of Mg-5Sn-0.3Li-0 and 3Zn multi-component alloys.The three dimensional(3D)morphology of the dendrite structure demonstrates the transition of the growth directions from<1123>,<1120>and<1122>to<1123>and<1120>due to the addition of Zn.The simultaneous effects of growing tendency and the decrement of dendrite coarsening rate at the solidification interval lead to dendrite morphology transition from the globular-like to the hyper-branch structure.This morphology transition results in the variation of the solidification macro-texture,which has effectively influenced the dominant deformation mechanisms(slip/twin activity).The higher activity of the slip systems increases the tendency of the dendrite arms for bending along the deformation direction and fragmentation.Apart from this,the dendrite holding hyper-branch structure with an average thickness below 20μm are more favorable for fragmentation.The dendrite fragmentation leads to considerable softening fractions,and as an effective strain compensation mechanism increases the workability of dendritic structure.
文摘The super-austenitic stainless steels are extensively utilized in the seamless tubes production for oil extraction industries. Due to the importance of thermo-mechanical processing in the production of these tubes, the dynamic recrystallization （DRX） characteristics of a Cr-Ni super austenitic stainless steel （1.4563） were investigated in the present study. This was performed using the hot compression testing method in the temperature range of 950-1150℃ and the strain rate of 10^-3-10^-1 s^-1. The initiation and evolution of DRX were examined through microstructural analysis. The results indicated that the recrystallized grain formed a necklace type structure at the prior austenite grain boundaries at higher strain rates. In addition, DRX nucleation occurs by bulging and successive strain induced boundary migration （SIBM）.
文摘Taguchi experimental design technique was applied to determine the most influential controlling parameters of FSP such as tool rotational speed,travel speed,tilt angle and penetration depth on hardness value of Mg.In this case,9 combinations of these 4 essential processing parameters were set and Taguchi's method followed exactly.Signal to noise ratio(S/N)analysis showed that maximum hardness achieved when rotational and travel speeds,penetration depth and tilt angel were chosen as 1600 rpm,63 mm/min,0.1 mm and 2°,respectively.In addition,analysis of variance(ANOVA)technique indicated that tilt angle and rotational as well as travel speed are the significant influential parameters in the hardness value of the treated samples,respectively.Finally a model for hardness values based on FSP parameters was calculated by design expert which was also confirmed by experimental results.
