铸辗成形环坯热压缩过程中晶粒的取向和织构演变

Evolution of Grain Orientation and Texture of Ring Shaped Blank Induced by Hot Compression During Casting-rolling Process

在不同变形温度和应变速率为0.1 s-1条件下研究了砂型铸造和离心铸造Q235B环坯的热压缩变形行为,并使用电子背散射衍射(EBSD)技术分析其晶粒取向和织构的演化特点。结果表明:Q235B环坯的晶粒在1000℃尺寸较小,有少量仍保持铸造状态的晶粒,组织演变的机理为动态回复和大应变几何动态再结晶;离心铸造环坯中有22%集中在20°-50°的大角度晶界。在1100℃再结晶充分,晶粒趋于等轴状;晶界取向差分布仍呈现典型的双峰特征,大角度晶界的比例为60%-75%。在1000℃砂型铸造Q235B的织构组态,为少量沿着<001>//ND取向线分布的{001}<100>立方织构和{001}<110>织构;在1100℃主要是高斯织构{110}<001>和沿着<110>//ND向{110}<001>方向移动并聚集的旋转立方织构{110}<110>。在1000℃离心铸造环坯的织构组态为旋转立方织构{110}<110>和铜型织构{112}<111>,Copper织构沿着ε-取向线分布;在1100℃主要为{001}<110>织构和沿着γ取向线由黄铜R{111}<112>向{111}<110>转变的织构,再结晶的程度高,取向密度大。

The characteristics for the evolution of grain orientation and texture of ring shaped blanks of sand-and centrifugal-casting Q235 B respectively were investigated by electron backscatter diffraction（EBSD） technique,while the blanks have been subjected to hot compression with a strain rate of 0.1 s＆-1at different temperatures.The results show that the grain size of the blanks after hot compression at 1000℃becomes smaller in the deformed microstructure,but a few grains maintains as in cast state.The mechanisms of the microstructure evolution may be ascribed to dynamic recovery and large strain geometric dynamic recrystallization.For centrifugal cast ones,the percentage of high-angle boundary in 20°-50° is22%,but after hot compression at 1100℃ it shows a homogenous microstructure with equiaxed grains because of sufficient recrystallization,while the mis-orientation distribution of grain boundaries still presents a typical characteristic of double-peaks and the proportion of the high-angle boundaries reaches to 60%-75%.The textures of sand casting Q235 B are a small amount cube texture {001}〈 100〉 and {001} 〈110〉along 〈001〉//ND at 1000℃,while the main textures are Goss texture {110} 〈001 〉and r-cube texture{110}〈001〉 at 1100℃.For centrifugal casting ones at 1000℃,{110}〈110〉 and Cu texture {112}〈111〉 dis-tributes along ε orientation;at 1100℃ the types of texture including {001}〈110〉 and {111}〈110 〉transformed from {111}〈112 〉along g orientation.The orientation density is higher due to the high extent of recrystallization.