不同冷却速度对Ti-6Al-4V钛合金热模拟试样组织的影响

Influence of different cooling rates on microstructure of Ti-6Al-4V titanium alloy thermal simulation specimens

采用Gleeble3500热模拟试验机对Ti-6Al-4V钛合金进行了焊接热模拟试验,采用金相显微镜、扫描电镜和X射线衍射仪分析研究了不同冷却速度对热模拟区域微观组织及显微硬度的影响.结果表明,冷却速度较低时,β晶界清晰完整,沿晶界向晶内形成片状α,随冷却速度的提高,α相减少,得到短小、纵横排列的针状α'组织;XRD标定表明随着冷速增加,主要形成六方结构的α'相,衍射谱与母材相比受到一些冲刷;母材硬度较低,热模拟区域的显微硬度随冷速增加也逐渐增大,但效果并不明显.

A simulation test of Ti-6Al-4V titanium alloy was made by means of the welding thermal simulation technique.The microstructure and phase composition characteristics of base metal and thermal simulation samples in different cooling rates were studied with optical microscope,scanning electron microscopy and X-ray diffraction analysis.The result demonstrates that the lamellar α is growth along the β grain boundary under the low cooling rate.When the cooling rate is increased,the acicular α′ martensite is formed along with the α-phase reduction.XRD analysis indicates that by comparing the thermal simulation specimens to the base metal,the diffraction peaks of the hexagonal close packed crystal α and α′ phases are subjected to some erosion.The microhardness increases with the increase of cooling rate,but the effect is not obvious.