TA19钛合金高温变形热加工图构建和微观组织演变

Processing Map Establishiment and Microstructure Evolution during Hot Deformation of TA19 Titanium Alloy

摘要:

利用Gleeble-3500热模拟压缩试验机,在变形温度820～980℃和应变速率0.01～10 s~(-1)的变形条件下,对TA19钛合金进行热模拟压缩试验,并根据动态材料模型(DMM)建立了其热加工图。同时,结合TA19钛合金微观组织分析,揭示了热变形工艺参数影响热加工图的内在原因。结果表明:变形工艺参数与能量耗散率和非稳态区密切相关。应变速率为0.01～1 s~(-1)时,能量耗散率较大,且随着变形温度的升高,能量耗散率先增大后减小,在940℃附近获得最大值。同时,变形失稳区包括2个典型区域,其中I区为(820～900)℃/(0.01～1) s~(-1),II区为(960～980)℃/(1～10) s~(-1)。变形温度为940℃时,较多的等轴α相和较高的再结晶驱动温度使得再结晶程度加强,因此能量耗散率获得最大值。绝热剪切带、片层α相与等轴α相之间的变形不协调以及β晶粒的剧烈长大是TA19钛合金高温变形失稳的主要原因。

Abstract:

Gleeble-3500 thermal simulation compression testing machine was used to conduct thermal simulation compression on TA19 titanium alloy with the deformation temperatures of 820 ～ 980 ℃ and strain rates of 0. 01 ～ 10 s~(-1).The processing map of TA19 titanium alloy was established according to dynamic material model( DMM). Meanwhile,based on microstructure observation of TA19 titanium alloy,the influences of deformation parameters on processing diagram were revealed. The results show that the deformation parameters largely influence the power dissipation efficiency and flow instability. The power dissipation efficiency is relatively large at the strain rates of 0. 01 ～ 1 s~(-1). As the deformation temperature increases,the power dissipation efficiency first increases and then decreases,and gets the maximum value near 940 ℃ . Meanwhile,the flow instability includes two typical regions,including region I of( 820～ 900) ℃/( 0. 01 ～ 1) s~(-1) and region II of( 960 ～ 980) ℃/( 1 ～ 10) s~(-1). At 940 ℃,the more equiaxed α grain and higher temperature strengthen the recrystallization degree,so the power dissipation efficiency can be maximized.Adiabatic shear band,uncoordinated deformation between lamellar and equiaxed α phase,and sharp growth of β grain are the main causes of flow instability of TA19 titanium alloy.