TC17(α + β)/TC17(β)钛合金线性摩擦焊接头相组成及织构分析

Study on phase and texture of TC17(α + β)/TC17(β) linear friction welding joint

关键词:  线性摩擦焊|钛合金|电子背散射衍射|织构

Key words:  linear friction welding|titanium alloy|electron backscatter diffraction|texture

摘要:

利用电子背散射衍射技术对TC17(α + β)/TC17(β)钛合金线性摩擦焊接头测试并分析，对接头各区域进行相鉴定和织构分析. 结果表明，与母材相比，焊态接头两侧热力影响区α相减少，β相增多. 由于焊缝区冷却迅速快，焊态焊缝处发生动态再结晶，生成了大量的亚稳定β相晶粒. TC17(β)侧母材及热力影响区的织构分布密度比TC17(α + β)侧强，且焊态焊缝区产生(5 4 6)[1 $\bar 3 \; \bar 3$]织构，轧面与(1 1 1)近似平行. 经过610 ℃热处理后，焊缝区亚稳定β相发生分解，形成细小的次生α相和β相. 与焊态焊缝相比，热处理后焊缝区晶体稍有转动，焊缝区织构强度较焊态有较大增强，形成(5 5 7)[$\overline {11}\; \overline {17}$ 20]织构. 热处理前后的焊缝区晶体取向都存在着ND方向与[1 1 1]靠近，轧面与(111)接近平行的择优取向.

Abstract:

The linear friction welded joints of TC17(α + β)/TC17(β) titanium alloy were tested and analyzed by electron backscatter diffraction technique. Phase identification and texture analysis were carried out on each part of the joint. The results show that compared with the parent metal, the α phase of thermo-mechanically affected zone decreases, and the β phase of the joint increases as weld. Due to the rapid cooling of the weld zone, dynamic recrystallization occurs at the weld joint, and a large number of metastable β phase grains are formed. The texture distribution density of TC17(β) side base metal and thermo-mechanically affected zone is stronger than TC17(α + β) side. The joint displayed texture (5 4 6)[1 $\bar 3$ $\bar 3$] in the as-welded weld zone. The rolling plane is approximately parallel to (1 1 1). After heat treatment at 610 °C, the metastable β phase of the weld zone decomposes to form a fine secondary α phase and β phase. Compared with the as-welded weld, the crystal of the weld zone is slightly rotated after postweld heat treatment, and the texture strength development, exhibited (5 5 7)[$\overline {11}\; \overline {17}$ 20] texture. The crystal orientation of the weld zone has a preferred orientation in which the normal direction is close to [1 1 1] and the rolling plane is close to (1 1 1).