【作者】 汶建宏；

【导师】 杨冠军； 葛鹏；

【作者基本信息】 西安建筑科技大学 ， 材料加工工程， 2008， 硕士

【摘要】 Ti-1300合金是西北有色金属研究院最近新研制出的一种超高强钛合金。该合金具有良好的可锻性和高淬透性,在1300MPa强度级别下具有良好的塑性和韧性匹配。该类型合金在固溶和时效过程中相变过程比较复杂,合金的组织和性能对热处理制度较为敏感。由于该合金是新合金,所以对其研究很少,这会限制其在航空航天工业领域的应用。基于上述考虑,本文研究了Ti-1300合金经常规固溶时效处理、固溶+随炉升温热处理以及固溶+锡浴时效处理后的显微组织和拉伸性能,采用X射线、OM、SEM、TEM等多种手段对Ti-1300合金固溶时效过程中的相变规律进行了研究,以期为该合金的应用提供一些参考。研究表明,Ti-1300合金在相变点之上固溶处理后为单一的等轴β组织,并且随着温度的降低,晶粒尺寸也在减小;相变点之下固溶处理后在β基体上析出颗粒状和针状α相。Ti-1300合金经790℃固溶+570℃时效处理后强度和塑性达到最佳匹配,这是因为在570℃时效时,相变驱动力和溶质原子扩散速度对α相变共同产生作用,使相转变速度达到最高值,组织中α相含量增多,使组织细化。Ti-1300合金在850℃固溶+随炉升温至400℃时开始发生β→ω转变,升温至500℃时,大部分β相已经转变成ω相,还有极少量α相的存在,当在570℃保温4小时后,ω相全部转变成α相。产生的ω相使得合金的强度迅速升高,而塑性却变差。因此,为使Ti-1300合金达到较好的强度和塑性的匹配,时效处理时应避免发生ω相变,故而时效处理温度应选择在500℃～600℃之间,时效时间选择在4小时左右。Ti-1300合金经850℃固溶+锡浴时效处理后发生β→α相转变,形成细晶强化,使合金的强度增加,塑性也得到提高。在β→α相转变过程中,晶界是优先形核的地方,这是因为晶界的切变阻力大,并且缺陷很多,这样可以产生能量差,保证α相的晶核出现。经锡浴处理后的Ti-1300合金比Ti-B19和Ti-B20具有更快的时效响应特征,并且其时效响应速率显著高于BETA-C、Ti-15-3等商用亚稳β钛合金。更多还原

【Abstract】 Ti-1300 alloy is a super high strength titanium alloy which developed by Northwest Institute For Non-ferrous Metal Research. This alloy has great forgeability and high hardenability, and optimum matching of plasticity and ductility under 1300MPa conditions. Ti-1300 alloy has complex phase transformation during solution and aging, its microstructure and propertity are sensitive to the heat treating regime. Because Ti-1300 alloy is newly, so we have little research on it, this will limit its application on aerospace industry.In order to offer some experiences of its applications, the microstructure and properties of Ti-1300 alloy treated by normal solution and aging, heated from room temperature after solution and tin bath after solution are studied in this paper. The phase transformation of Ti-1300 alloy during heat treatment is observed by means of XRD, OM, SEM and TEM .The results show that the microstructure of Ti-1300 alloy is single and equiaxedβphase after solution above the transformation point, the grain size reduced with the temperature decreased, and the granular and needleαphase was observed inβmatrix after solution above the transformation point.Ti-1300 alloy owned optimal strength and plastic by aging at 570°C after solution at 790℃, because the interaction of phase transformation driving force and solute atoms diffusion velocity made moreαphase was observed in the matrix, andαphase refining the structure.Theωtransformation occurred when Ti-1300 alloy was heated to 400℃from room temperature after soluted at 850℃for 1 hour. When the alloy was heated to 500℃, most βphase changed toωphase, there is still a fewα. When it kept worm for 4 hours later,ωphase transformed intoαphase. Theωphase made the strength of the alloy rise rapidly, but plasticity decreased. So theωphase must be avoided when aging treatment in order to get the best properties, therefore, the aging treatment temperature should be chose between 500℃～600℃and time should be chose for 4 hours.The strength and plastic was increased by fine grain strengthening after Ti-1300 alloy was soluted at 850℃for 1 hour. Duringβ→αphase transformation, it was observed thatαphase nucleated at grain boundary firstly, because grain boundary had big shear resistance and many defects, it can produce energy difference and ensureαphase appearance.The aging response character of Ti-1300 alloy after tin bath is more quickly than that of Ti-B19 and Ti-B20, moreover, the aging response rate is higher than BETA-C and Ti-15-3 of metastableβtitanium alloys in business application.更多还原