钛锆二元合金过冷β相的形成与转变  

Formation and Transformation of Supercooled β Phase in Ti-Zr Binary Alloys

作　　者：李敏[1] 汪涛[1] 汤武[1] 柏佳[1] 缪润杰 

机构地区：[1]南京航空航天大学材料科学与技术学院,江苏南京211106

出　　处：《稀有金属》2016年第4期301-306,共6页Chinese Journal of Rare Metals

基　　金：江苏省科技支撑计划(社会发展)项目(BE2010730)资助

摘　　要：以海绵钛和海绵锆为原材料通过水冷铜模电弧熔炼制备出含20%-70%Zr（质量分数）的钛锆二元合金,采用X射线衍射（XRD）、显微组织观察和差示扫描量热法（DSC）表征了热处理前后合金相组成及相转变规律。本文采用了两种热处理方法：一方面把Ti-60Zr加热到α/β转变临界温度以上（1000℃）等温后缓慢冷却至室温;另一方面研究了Ti-60Zr在α/β转变临界温度以下进行300和400℃等温热处理获得单相α相的情况。结果表明：在水冷铜模电弧熔炼获得的钛锆合金试样中除Ti-20Zr为α相以外,其他成分的合金均由α＋β两相组成,其中Ti-60Zr几乎全部为β相;显微组织观察得出α型钛锆合金为针状结构,β型钛锆合金为等轴晶。平衡相图中α＋β两相区的宽度直接影响过冷β相的形成能力,在同样的冷却速率下,两相区越窄的合金成分在冷却过程中越容易形成过冷β相。以10℃·min^-1升温速率从室温升温至1000℃等温2 h后以5℃·min^-1的冷却速率降至室温和以10℃·min^-1升温速率从室温升温至400℃等温2 h后炉冷至室温两种热处理方法,均能实现Ti-60Zr合金过冷β相向α相的完全转变。Six specimens of binary Ti-Zr alloys with zirconium contents（ mass fraction） ranging from 20% to 70% were prepared from titanium sponge and zirconium sponge by arc melting with water-chilled copper hearths. X-ray diffraction（ XRD）,metallographic observation and differential scanning calorimetry（ DSC） were employed to analyze phase composition and phase transformation during the preparation and further heat treatment of Ti-Zr alloys. Two methods of heat treatment were employed. Firstly,Ti-60 Zr alloy was heated above the critical temperature of α / β transformation（ 1000 ℃）,soaking for 2 h,and then cooled to room temperature at very low cooling rates. Secondly,the acquisition of single α phase of Ti-60 Zr after isothermal heat treatment at 300 and 400 ℃,which was below the critical temperature of α / β transformation,was also investigated. The results showed that apart from Ti-20 Zr,Ti-Zr alloys prepared by arc melting with water-chilled copper hearths formed supercooled β phase during cooling and a significant amount of supercooled β phases were observed in as-prepared Ti-60 Zr alloy. In addition,α phase showed an acicular structure and the β phase was an equiaxial structure in Ti-Zr alloys indicated by the metallographic observation. Moreover,the quantity of supercooled β phase was inversely proportional to the width of two-phase region. At the same cooling rates,the narrower the two-phase region was,the more easily the β phase formed. The supercooled β phase of Ti-60 Zr alloy could transform into α phase with methods of re-heating to 1000 ℃ at10 ℃·min^- 1 for 2 h and cooling to room temperature at 5 ℃·min^- 1,and re-heating to 400 ℃ at 10 ℃·min^- 1for 2 h and furnace cooling to room temperature.

关 键 词：过冷β相 钛锆合金 差示扫描量热法 热处理 相变 

分 类 号：TG146.4[一般工业技术—材料科学与工程]