Ti-4.4Al-3.8Mo合金的亚稳相变及其对硬度的影响

对锻态 Ti-4Al-3.8Mo合金分别进行了β单相区和α β两相区(相变点之下45℃)淬火处理,研究了亚稳相变对硬度的影响.结果表明,β单相区淬火处理的样品硬度比α β两相区处理的样品高约10%.β单相区淬火后的相组成为全α'马氏体,自910℃的α β两相区淬火后的相组成为等轴初生α相 α'马氏体 α"马氏体.硬度出现差异的主要原因是后者中存在硬度较低的初生α相和α"马氏体.本文修正了Ti-β稳定元素二元系亚稳相图(示意图),指出在α α'和α α"相区之间存在α α' α"相区,并使用修正后的相图解释了Ti-4.4Al-3.8Mo合金的相组成与硬度的关系.     

固溶温度对Ti-5Mo-5V-2Cr-3Al钛合金棒材组织和性能的影响规律

研究了固溶温度对Ti-5Mo-5V-2Cr-3Al钛合金棒材显微组织和力学性能的影响。结果表明,钛合金固溶处理温度在相变点以下,空冷后,显微组织由β相、初生α相以及次生α相组成。随着固溶温度的升高,显微组织中β相晶粒尺寸增大,晶界α相厚度减小,产生有序化现象,而次生α相数量和尺寸减小,使合金的强度降低,塑性升高,但固溶处理温度为800℃时,网状晶界α相使塑性迅速下降;当固溶处理温度在相变点以上,Ti-5Mo-5V-2Cr-3Al钛合金重新形核并长大,随着固溶温度的升高,β相晶粒尺寸增大,初生α相数量减少,强度和塑性都下降,过冷β相晶粒发生应力诱发马氏体现象。     

固溶温度对Ti-4Al-6Mo-2V-5Cr-2Zr钛合金的组织和拉伸性能的影响

研究了固溶温度对一种亚稳β钛合金(Ti-4Al-6Mo-2V-5Cr-2Zr)的锻态组织和室温拉伸性能的影响。结果表明,固溶温度低于相变点时大量的α相在β基体中析出并聚集在滑移带附近,随着固溶温度接近相变点α相的数量减少且部分滑移带消失。固溶温度高于相变点时显微组织为单一的β相且滑移带完全消失,随着固溶温度继续升高β晶粒聚集且长大。这种合金经750℃×1 h固溶处理后达到良好的强度塑性匹配,气抗拉强度、屈服强度和伸长率分别为957 MPa、887 MPa和11.7%。     

Ti-4．4A1—3．8Mo合金的亚稳相变及其对硬度的影响

对锻态Ti-4．4Al-3．8Mo合金分别进行了β单相区和α＋β两相区（相变点之下45℃）淬火处理,研究了亚稳相变对硬度的影响．结果表明,β单相区淬火处理的样品硬度比α＋β两相区处理的样品高约10％．β单相区淬火后的相组成为全α’马氏体,自910℃的α＋β两相区淬火后的相组成为等轴初生α相＋α’马氏体＋α″马氏体．硬度出现差异的主要原因是后者中存在硬度较低的初生α相和α″马氏体．本文修正了Ti—β稳定元素二元系亚稳相图（示意图）,指出在α＋α’和α＋α″相区之间存在α＋α’＋α″相区,并使用修正后的相图解释了Ti-4．4Al-3．8Mo合金的相组成与硬度的关系．     

热处理对Ti-6Mo-5V-3Al-2Fe-2Zr合金拉伸性能的影响

研究了固溶+单级时效处理、固溶+双级时效处理、固溶+随炉冷却处理对新型亚稳β钛合金Ti-6Mo-5V-3Al-2Fe-2Zr的显微组织和拉伸性能的影响。结果表明：与固溶+单级时效处理相比,固溶+双级时效处理析出的晶内次生α相间距减小和体积分数增大而使合金的强度提高。两种热处理都使合金中生成连续的晶界α相,导致合金的塑性降低;与上述两种热处理相比,固溶+随炉冷却处理使合金中析出的晶内次生α相的间距明显减小且沿晶界生成向晶内生长的α_wgb相,使合金的强度和塑性显著提高,其抗拉强度达到1421 MPa,断后伸长率为7.7%;与次生α相的体积分数相比,其间距是影响合金强度的主要因素。随着次生α相间距的减小,合金的强度提高。     

固溶温度对亚稳β钛合金Ti-4Mo-6Cr-3Al-2Sn的组织和拉伸性能的影响

对自主设计的新型亚稳β钛合金Ti-4Mo-6Cr-3Al-2Sn(%,质量分数)在不同温度进行固溶和固溶时效处理,观察其显微组织和测试室温拉伸性能。结果表明：随着固溶温度的提高固溶态组织中的初生α相减少,当固溶温度高于相变点后初生α相完全消失,几乎全部为明显长大的粗大β晶粒。固溶温度为900℃的固溶态合金具有良好的强度和塑性匹配,屈服强度为898.7 MPa、抗拉强度为962.5 MPa、断裂伸长率为12.7%。在不同温度固溶处理的时效态合金,均析出了细小的次生α相。固溶温度低于相变点时,在初生α相间析出的细小次生α相呈60°或者平行交错排列;固溶温度高于相变点时初生α相几乎完全消失,随着固溶温度的提高析出的次生α相片层间距变大并粗化。在所有固溶温度下,时效态组织中沿原始β晶界处均析出了连续的晶界α相,合金的塑性均较差。经过750℃/0.5 h固溶和500℃/4 h时效的合金具有良好的强度和塑性匹配,其抗拉强度为1282 MPa,屈服强度为1210.6 MPa,断裂伸长率为5.3%。     

Superplasticity of a Ti-24Al-14Nb-3V-0.5Mo Intermetallic Alloy

Superplastic properties and microstructural evolution of a Ti-24Al-14Nb-3V-0.5Mo (at. pct) intermetallic alloy were studied. Optimum superplastic properties were obtained for temperatures in the interval 960℃≤5 T≤5980℃. The apparent activation energy in the superplastic regime was determined and the deformation mechanism was also discussed. Based on the studies, a curve panel with three sheets sandwich structure was fabricated successfully. The microstructures corresponding to different strain in the part were also studied.     

Hydrogen Effects on the Mechanical Properties of Ti-24Al-11Nb-3V-1Mo Alloy

The effects of hydrogen on the mechanical properties at room temperature of a Ti3Al based alloy Ti-24Al-11Nb-3V-1Mo have been investigated. The results show a parabolic rate relationship between the average hydrogen concentration of the alloy at constant temperature and charging time. The mechanical properties (ultimate bending strength and deflection) decrease with increasing hydrogen content in the alloy. The fractographic feature indicates that the decrease of the mechanical properties is due to the crack nucleation and propagation at the hydride Ti3AIH     

Adiabatic shear band in a Ti-3Al-5Mo-4.5V Titanium alloy

An investigation has been carried out on the adiabatic shear band (ASB) in a Ti-3Al-5Mo-4.5V (TC16) alloy deformed at high strain rate by a split Hopkinson pressure bar (SHPB). ASB in TC16 alloy is a “white” band with a width of about 13 μm. Microhardness of the ASB is larger than that of the matrix. The elongated cell structures of width about 0.2–0.5 μm with thick dislocation exist in the boundary of the shear band. Results suggest that the fine equiaxed grains with α-phase and α″-phase coexist in the shear band. The “white” band is a transformation band. Calculation of the adiabatic temperature rise indicates that the maximum temperature within ASB is about 1,069 K that is above the phase transformation temperature. Finally, formation of an ASB in the TC16 alloy and its microstructure evolution are described.     

Ti—25Al—10Nb—3V—1Mo合金的高周疲劳性能及断裂特征

实验测定了Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ合金６５０℃下高周疲劳Ｓ－Ｎ曲线及热暴露后合金的疲劳性能。结果表明，Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ合金具有较高的疲劳强度，可以满足转子零件的要求。对比光滑和缺口试样的高周疲劳性能，可以看出该合金缺口敏感程度高，且随着应力水平的增加而增大。     

退火温度对冷轧Ti-13V-3Al-0.5Cu形状记忆合金组织结构与马氏体相变的影响

使用XRD、TEM、DSC和室温拉伸等分析测试手段,对冷轧后经不同退火温度处理的Ti-13V-3Al-0.5Cu(%,原子分数)合金微观组织结构,马氏体相变行为,力学性能和形状记忆性能进行了研究。经冷轧、退火处理后,合金在室温下的组织主要为α"马氏体相,存在少量残余β母相、α相和Ti₂Cu第二相。随着退火温度的增加,合金形状记忆性能先升高后降低;当退火温度为750℃时,在预应变量为6%的前提下可实现5.3%的可回复应变。其组织结构观察结果表明,经冷轧、退火处理后,合金中α"马氏体形貌由“V”字型自协作组态向择优取向的单一取向马氏体板条转化,界面可动性提升,马氏体临界再取向应力降低,形状记忆性能提高。     

Texture Evaluation of α_2 Phase in Ti-25Al-10Nb-3V-1Mo Alloy Sheet

The texture evaluation of α2 phase in Ti-25Al-10Nb-3V-1Mo sheet during rolling and annealing has been investigated by means of microstructure observation and ODF analysis. From the weak initial {1010} (1210) and {0001}(1210) textures a {1210}(1010) texture and a {0001}(uvtw)fibre texture are formed after cold rolling. The {0001} (1210) texture is also strengthened simultaneously. The activation process of slip systems is discussed concerning formation of the rolling texture. Because of the disappearance of {0001} (nvtw) fibre texture the primary recrystallization process should occur and the {1210}(1010) texture forms during annealing     

Ti−6Mo−5V−3Al−2Fe−2Zr合金热变形行为及热加工图

目的 建立近β钛合金Ti−6Mo−5V−3Al−2Fe−2Zr(质量分数)的热变形本构方程,绘制热加工图,确定该合金的流变失稳区和适宜加工区,为其在工业生产中热加工工艺参数的制定提供指导。方法 在变形温度700~ 850 ℃、应变速率0.000 5~0.5 s⁻¹、真应变0.7的条件下,对近β钛合金Ti−6Mo−5V−3Al−2Fe−2Zr进行热压缩实验;基于Arrhenius方程建立该合金的热变形本构方程,并对方程进行验证;根据Prasad失稳准则,构建该合金的热加工图。结果 该合金的流变应力随着变形温度的升高而减小,随着应变速率的增大而增大;其热变形激活能为226.29 kJ/mol,本构方程为;通过热变形本构方程得到的峰值应力计算值与实验值平均误差为4.21%。结论 建立的热变形本构方程预测了流变应力,描述了该合金的热变形行为;通过叠加合金的能量耗散图和流变失稳图,获得了该合金的热加工图。基于热加工图确定该合金的流变失稳区为变形温度700~755 ℃与784~850 ℃、应变速率0.5~0.05 s⁻¹,最佳加工区为变形温度836~850 ℃、应变速率0.000 5~0.005 s⁻¹。