周晓光
,
刘振宇
,
吴迪
,
王国栋
,
刘相华
金属学报
利用Gleeble-2000热/力模拟实验机模拟了柔性化薄板坯连铸连轧(FTSR)生产线轧制低碳含Nb钢的动态软化行为. 根据不同Nb含量试样在不同变形温度下的应力-应变曲线, 得出Nb含量对动态再结晶数学模型中各参数的影响规律.结果表明: 随Nb含量的增加, 动态再结晶激活能逐渐增加, 且高于传统流程的动态再结晶激活能; 随Nb含量的增加, 模型参数中A值线性增加, Avrami指数m线性减小, n值线性增加, B值逐渐增加, 动态再结晶变得困难. 所计算的动态再结晶率以及峰值应力与实测的结果吻合良好.
关键词:
柔性化薄板坯连铸连轧
,
Dynamic recrystallization
,
Nb bearing steel
M. Shaban
材料科学技术（英文）
A low carbon Nb-Ti microalloyed steel was subjected to hot torsion testing over the temperature range 850-1100°C and strain rates 0.01-1 s-1 to study the influence of deformation conditions on the dynamic recrystallization characteristics of austenite. The results show that dynamic recrystallization occurs more easily with the decrease of strain rate and the increase of deformation temperature. The complete dynamically recrystallized grain size as a function of Zener{Hollomon parameter was established. It was found that dynamically recrystallized grain sizes decrease with increasing strain rate and decreasing deformation temperature. The effect of microalloying elements on peak strain was investigated and the solute drag corrected peak strain was determined. Also, the dynamic recrystallization map of austenite was obtained by using recrystallization critical parameters.
关键词:
Dynamic recrystallization
Shuai WANG
金属学报(英文版)
Hot compression test was carried out at 1000 ℃ to investigate the dynamic recrystallization nucleation mechanism of a nickel-base superalloy. It was found that the bulging of original grain boundaries was inhibited by carbides and deformation twins at the boundaries. Recrystallized nuclei evolved from the subgrains of dislocation reconfiguration along original grain boundaries, and the growth of the potential nuclei was carried out by the coalescence of subgrains. The necklace structure of recrystallized grains along original grain boundaries was attributed to the strain gradient from grain boundary to grain interior.
关键词:
Dynamic recrystallization
Baojun YU
金属学报(英文版)
A dynamic recrystallization (DRX) cellular automaton (CA) model that can mark the microstructure with DRX circle was developed. The effects of initial grain size on the stress-strain curve, mean grain size and DRX fraction were mainly investigated, and the simulated results were compared with those obtained from previous researches. The results show that the shape of the stress-strain curve is sensitive, while the stress and mean grain size at the steady state are insensitive to the initial grain size. The transition from a multiple-peak stress-strain curve to a single-peak one can be explained by variations in DRX circle fraction, and the initial grain size to make this transition is between 70 and 80 μm.
关键词:
Dynamic recrystallization
Wenchen XU
材料科学技术（英文）
Hot compression tests were conducted on a Gleeble-1500 simulator to investigate the hot deformation behavior of BT20 Ti alloy (Ti-6Al-2Zr-1Mo-1V) in the temperature range from 550 to 1000℃ at constant strain rate in the range of 0.01~1 s-1, and then the optimum spinning temperature range was determined. Moreover, tube spinning experiments were executed to verify the reasonability of the optimum temperature range. The results show that the flow stress declines gradually with increasing deformation temperature and decreasing strain rate. In α+β phase region the dynamic recrystallization is the main softening mechanism and in β phase region the hot deformation softening is controlled by dynamic recovery. In α+β phase region with reducing strain rate dynamic recrystallization is fully developed. The optimum temperature of hot spinning is 850~900℃ and that of warm spinning is 600~650℃. Meanwhile, at the temperature above 600℃ tubular workpieces of BT20 Ti alloy have been spun without surface cracks and microstructure inhomogeneity, which proves that the optimum spinning temperature range obtained through hot compression experiments is reasonable.
关键词:
Dynamic recrystallization
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null
,
null
,
null
M. Shaban
材料科学技术（英文）
A low carbon Nb-Ti microalloyed steel was subjected to hot torsion testing over the temperature range 850-1100°C and strain rates 0.01-1 s-1 to study the influence of deformation conditions on the dynamic recrystallization characteristics of austenite. The results show that dynamic recrystallization occurs more easily with the decrease of strain rate and the increase of deformation temperature. The complete dynamically recrystallized grain size as a function of Zener{Hollomon parameter was established. It was found that dynamically recrystallized grain sizes decrease with increasing strain rate and decreasing deformation temperature. The effect of microalloying elements on peak strain was investigated and the solute drag corrected peak strain was determined. Also, the dynamic recrystallization map of austenite was obtained by using recrystallization critical parameters.
关键词:
Dynamic recrystallization
A.Momeni
,
A.Shokuhfar
,
S.M.Abbasi
材料科学技术（英文）
In this research, the dynamic recrystallization (DRX) behavior of an as-cast precipitation hardenable (PH) stainless steel was investigated by conducting hot compression tests at temperatures between 950–1150oC and under strain rates of 0.001–1 s-1. The flow stress curves show that the DRX is responsible for flow softening during hot compression. The effects of temperature and strain rate on the strain and stress corresponding to peak point (ξp and θp) of flow curve were analyzed individually. It is realized that, they increase with strain rate and decrease with temperature. The relationship between Zener-Hollomon parameter (Z) and ξp was investigated and the equation ofξp =4.3×10-4Z0.14 was proposed. The strain for the maximum rate of DRX (ξmax) was determined under different deformation conditions. Therefore, it is realized that it increases with Z parameter and vise versa. On the basis of obtained results, the equation ofξmax =9.5×10-4Z0.12 was proposed.
关键词:
Dynamic recrystallization
,
null
,
null
M.Jafari
,
A.Najafizadeh
材料科学技术（英文）
Several methods have been proposed to calculate the critical stress for initiation of dynamic recrystallization (σc) on the basis of mathematical methods. One of them is proposed by Stewart et al. in which this critical point appears as a distinct minimum in the (-dθ/dσ vs σ) through differentiating from θ vs σ. Another one is presented by Najafizadeh and Jonas by modifying the Poliak and Jonas method. According to this method, the strain hardening rate was plotted against flow stress, and the value of σc was attained numerically from the coefficients of the third-order equation that was the best fit from the experimental θ-σ data. Hot compression tests were used in the range of 1000 to 1100℃ with strain rates of 0.01–1 s-1 and strain of 1 on 316 stainless steel. The result shows that Najafizadeh and Jonas method is simpler than the previous one, and has a good agreement with microstructures. Furthermore, the value of normalized critical stress for this steel was obtained μc=σc/σp=0.92.
关键词:
Dynamic recrystallization
,
null
,
null
Gang Wang
材料科学技术（英文）
The hot deformation behavior of a Ti-47Al-2Cr-2Nb-0.2W-0.15B (at.%) titanium aluminide alloy fabricated by pre-alloyed powder metallurgy has been investigated by using the hot compression tests in the temperature range from 950°C to 1300°C and at the strain rates between 10-3 s-1 and 10 s-1. The processing maps have been established to evaluate the optimum hot processing conditions and reveal the instability regions. It is found that the flow stress of the investigated alloy is a strong function of the temperature and the strain rate. The investigated alloy has the optimum hot-working condition at 950°C and 10-3 s-1, since the material undergoes dynamic recrystallization to produce a fine-grained microstructure. At 1250°C and 10-3 s-1, the
alloy exhibits superplastic deformation. At 1300°C and 10-1 s-1, the cyclic dynamic recrystallization with high temperature grain coarsening takes place. The material undergoes flow instabilities at lower temperatures and higher strain rates, as predicted by the instability criterion. The processing maps demonstrate that the strain significantly affected the instability regions. The manifestations of the instabilities have been observed in the form of microvoids, wedge cracks, and surface fractures.
关键词:
Titanium aluminide
Yinong WANG
,
J.C.Huang
材料科学技术（英文）
A two-stage strain rate deformation method is proposed to enhance the superplasticity in a hot extruded AZ61 alloy. In the stage-one of deformation, a relatively high strain rate was applied in order to obtain fine grains through dynamic recrystallization. The optimum strain rate for DRX at 300℃ was identified as ～5×10-3 s-1. Stage-two is conducted at relatively low strain rate in order to utilize the fine grains refined by DRX during stage-one to make the grain boundary sliding operate more smoothly, which resulting in enhanced superplastic elongation from 350% to 440%.
关键词:
AZ61 magnesium alloy
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null
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null
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null
