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1.
粉末冶金TiAl合金热变形行为及加工图的研究   总被引:1,自引:1,他引:1  
采用热模拟压缩试验研究了粉末冶金TiAl合金在温度1000~1150℃、应变速率0.001~1s~(-1)范围内的高温变形特性,发现合金的流动应力-应变曲线具有应力峰和流变软化特性.为了研究TiAl合金在有限应变下的变形行为,基于动态材料模型(DMM)建立起了TiAl合金加工图.试验结果表明,在高应变速率(>0.1s~(-1))变形时,材料落人流动失稳区域,出现表面开裂.这对材料的变形是有害的,要避免在流动失稳区进行热加工处理.而在温度为1000~1050℃,应变速率为0.001~O.01s~(-1)时,功率耗散率η值在35%~50%之间.这个区域对应的变形机制为动态再结晶,适合进行热加工.在高温(≥1100℃),低应变速率(0.001s~(-1))变形时,功率耗散率η达到最大值60%,此时材料发生超塑性变形.  相似文献
2.
利用Gleeble-3800热模拟试验机,对一种新型二次硬化渗碳钢C61进行了高温轴向压缩试验,测得其高温流变曲线,观察了高温变形后的显微组织,获得了该钢的热变形激活能Q为414.84 kJ/mol,建立了试验钢的热变形本构方程,并绘制了其热加工图.结合高温变形后的显微组织和热加工图,确定最优热变形工艺参数为变形温度范围为1050~1100℃,应变速率范围为0.1~1.0 s-1,此时试验钢组织发生了完全动态再结晶,晶粒明显细化,且对应的能量耗散效率达到峰值.  相似文献
3.
李红斌  于恩林 《钢铁》2016,(9):63-69
利用Gleeble-3500热模拟试验机研究了不同变形温度(550、600、650、700℃)和不同变形速率(0.001、0.01、0.1、1、10 s-1)对热轧态中碳钢温变形过程中变形行为的影响,并结合热加工图探明了在细小晶粒铁素体基体上形成均匀分布细小渗碳体颗粒复相组织的最佳工艺窗口。结果表明,温变形过程中,会发生铁素体再结晶以及渗碳体片层动态球化行为,其微观组织演变对流变应力影响较大;根据绘制的热加工图,温变形的适宜温度区间为630~700℃,速率区间为0.30~10和0.001~0.007 s-1,在该工艺区间变形,初始组织转变为细小均匀铁素体基体上分布着细小粒状渗碳体的复相组织。  相似文献
4.
运用Gleeble-3800热模拟试验机研究了1Cr17Ni1马氏体-铁素体双相不锈钢在变形温度为950~1150℃、应变速率为0.1~10 s-1条件下的热压缩变形行为。运用双曲正弦函数构建了本构方程,得到了表观激活能为391.586 kJ/mol,并基于动态材料模型绘制了1Cr17Ni1钢不同应变量下的热加工图。观察变形后的组织形貌得到较低温度下发生动态回复与动态再结晶,较高温度只发生动态回复,综合热加工图与变形后组织得到最佳热变形工艺:热加工温度范围为950~1000℃、热加工变形速率范围为0.1~0.3和5~10 s-1。  相似文献
5.
采用Gleeble-3500热模拟试验机进行高温等温压缩实验,研究了GH690合金在变形温度为950~1200℃、应变速率为0.001~10.000 s-1条件下的热变形行为,利用动态材料模型构建了GH690合金热加工图,并基于加工图进行GH690合金管材热挤压实验。结果表明:GH690合金有应力峰和动态再结晶软化的特征,在ε≥0.4时,流动应力趋于稳定状态;在热加工图中变形温度为1100~1150℃、应变速率为1.0~2.5 s-1时功率耗散效率达到0.34~0.39,该区域对应的工艺参数适合于进行GH690合金管材热挤压;在热加工图中变形温度为950~1000℃,应变速率在0.94~10.00 s-1之间的区域为不稳定变形区域,热加工时应该避开这一区域。  相似文献
6.
随着精密成形技术的发展,对热锻工艺的要求越来越严格,采用建立材料的物理模型及热加工图这一方法来优化最佳工艺条件,为实现产品的质量精确控制提供了科学保障.通过Gleeble-3800热模拟试验机对20CrMnTiH钢在变形温度为850~1150℃,应变速率为0.01~10 s-1条件下进行等温热压缩试验,研究了20CrMnTiH钢的热压缩变形特性,采用Zener-Hollomon参数法建立了20CrMnTiH钢高温塑性变形的物理模型;并以热压缩试验为基础,绘制了20CrMnTiH钢的三维热加工图并进行分析,确定了该钢的最佳热成形工艺参数.通过流变曲线可以看出,20CrMnTiH钢在热成形过程中发生了明显的动态回复与动态再结晶,流变应力随应变速率的增加而增加,随变形温度的升高而降低;由热加工图分析得到了该钢在试验参数范围内较优的热加工工艺参数,加工温度为900~1025℃,应变速率为0.01~0.2 s-1.  相似文献
7.
W. Feng  F. Qin 《钢铁冶炼》2018,45(4):317-324
The processing map of 20CrMnTiH steel is developed by using the dynamic material model according to the hot compression experiments, performed on a Gleeble-3500 thermal simulator at the temperature range of 850–1150°C and the strain rate of 0.01–1?s?1. Hot workability characteristics of 20CrMnTiH steel are analysed based on the developed processing map. The safe deformation regions with higher power dissipation efficiency η exhibit the dynamic recrystallisation (DRX) mechanism and show fine and homogeneous microstructure. The unstable regions with negative instability coefficient ξ occur at both lower temperature with all strain rates and at high temperature with high strain rate at the strain of 0.2. The area of instability gradually decreases with the increasing strain and only appears at lower temperature and higher strain rate when the strain is above 0.2. The unstable regions indicate the flow localisation by microstructure analysis. Combining with the developed processing map with DRX behaviour, the optimal values of hot processing parameters for 20CrMnTiH steel are obtained to achieve good hot workability and small grains sizes at the process parameters ranged at 1036–1070°C/0.1–1?s?1 and 918–985°C/0.01–0.014?s?1.  相似文献
8.
 A finite element model is made for coupled thermo-mechanical analysis during hot continuous rolling process for finished product- Inconel 718 alloy round rod with diameter of 45mm. The stability of that process is discussed by integration of FEM and processing map reported in open literature. The result shows that the stability of Inconel 718 will be analyzed effectively during that process and good stability appears as the initial temperature is 960℃ and the initial velocity is from 0.15 to 0.45m•s-1 or the initial temperature is 980℃ and the initial velocity is from 0.15 to 0.25m•s-1.  相似文献
9.
The behavior evolvement of Mg-9Y-1MM-0.6Zr (WE91) alloy during hot deformation process was discussed. The flow stress behavior of magnesium alloy over the strain rate range of 0.001 to 1 s-1 and the temperature range of 653 to 773 K was studied on a Gleeble-1500D hot simulator under the maximum deformation degree of 60%. The experimental results showed that the relationship between stress and strain was obviously affected by the strain rate and deformation temperature and the flow curves observed were typical of the occurrence of dynamic recrystallization. The flow stress of WE91 magnesium alloy during high temperature deformation could be represented by the Zener-Hollomon parameter in the hyperbolic Arrhenius-type equation. The average deformation activation energy Q and strain coefficient n were 224.11 kJ/mol and 3.08 by calculation,respectively. The processing maps were calculated and analyzed according to the dynamic materials model. The map at strain of 0.916 exhibited three domains with peak efficiency of 49%,44% and 42%,respectively. It was found that the alloy could be extruded at 693 K with mechanical properties of σ0.2=240 MPa,σb=315 MPa and δ=15.5%.  相似文献
10.
在Cleeble-1500热/力模拟机上对2026合金进行了热压缩试验,研究了其在温度300~450℃和应变速率0.01~10 s-1条件下的热变形行为.结果表明:热变形过程中的流变应力可以很好用双曲正弦本构关系来描述,通过优化α值,可以更精确地得到该合金的表观激活能为230.51kJ/mo1.根据材料动态模型,计算并分析了2026合金的加工图.利用加工图确定了热变形的流变失稳区,合金在热加工温度450℃,应变速率为0.01s-1时可加工性最优.  相似文献
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