Microstructural characterisation of near-α titanium alloy Ti-6Al-4Sn-4Zr-0.70Nb-0.50Mo-0.40Si
Microstructural characterisation of near-α titanium alloy Ti-6Al-4Sn-4Zr-0.70Nb-0.50Mo-0.40Si
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DOI：
10.1007/bf02668196
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发表时间：
1993-06
期刊：
影响因子：
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通讯作者：
C. Ramachandra;A. Singh;G. Sarma
中科院分区：
文献类型：
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作者：
C. Ramachandra;A. Singh;G. Sarma
研究了含Ti-6Al-4Sn-4Zr-0.70Nb-0.50Mo-0.40Si的近α钛合金（834合金）在β和（α + β）固溶和淬火条件下的组织稳定性。该合金的β横截面约为1333k。在1353 K下进行β相场固溶处理，然后在室温水中淬火，形成具有高位错密度和层错的α′马氏体薄片。发现β薄膜夹在界面相之间，而界面相又夹在板条马氏体的板间边界处。界面阶段是一个在文献中有很多争议的主题。在1303 K （α + β）相场中固溶处理，然后在室温水中淬火，得到近等轴的初生α和相变β。β和（α + β）固溶处理试样均在873 ~ 973 K温度范围内时效。在973 K时效处理时，（α+ β）处理的试样，即使在873 K的低温下时效24小时，也主要在马氏体板条的板间边界处析出自杀。电子衍射分析证实它们为六方自杀s2， a= 0.702nm, c =0.368nm。析出的上述差异可归因于（α + β）固溶条件下大量β稳定元素和硅化元素分配到转化的β中。然而，在所有老化条件下都观察到α′相的有序性。结构域的有序是由于时效时间的延长，导致α-稳定元素水平的局部升高。
Microstructural stability in the near-α titanium alloy (alloy 834) containing Ti-6Al-4Sn-4Zr-0.70Nb-0.50Mo-0.40Si (in weight percent), in the β and(α + β)solution-treated and quenched conditions, has been investigated. The β transus for this alloy is approximately 1333 K. Solution treatment in the β phase field at 1353 K followed by quenching in water at room temperature resulted in the formation of α′ martensite platelets with high dislocation density and stacking faults. Thin films of β are found to be sandwiched between interface phases, which, in turn, are sandwiched at the interplatelet boundaries of lath martensite. The interface phase is a subject of much controversy in the literature. Solution treatment at 1303 K in the(α + β)phase field followed by quenching in water at room temperature resulted in the near-equiaxed primary α and transformed β. Both the β and(α + β)solution-treated specimens were aged in the temperature range of 873 to 973 K. While aging the —treated specimen at 973 K,(α+ β)-treated specimen, even at a lower temperature of 873 K for 24 hours, caused precipitation of suicides predominantly at the interplatelet boundaries of martensite laths. Electron diffraction analysis confirmed them to be hexagonal suicide S2witha= 0.702nm andc =0.368nm. The above difference in the precipitation could be attributed to the partitioning of a higher amount of β-stabilizing elements as well as silicide-forming elements to the transformed β in the(α + β)solution-treated condition. However, ordering of theα′ phase was observed under all of the aging conditions studied. The ordered domains were due to the longer aging times, which cause local increases in the level of theα-stabilizing elements.