Grain Refining and Texture Control of Nonferrous Metals through High Speed Hot Rolling

研究了热轧条件对Ti-6Al-4V合金、Ti-15V-3Cr-3Sn-3Al合金和无氧铜淬火板材组织的影响。在高速热轧Ti6Al-4V板材时，剪切变形会在表面下产生严重的剪切区。剪切应变随轧制温度的升高而增大，随轧制表面摩擦系数的减小而减小。在α + β区轧制的薄板的严重剪切区出现极细的等轴α晶粒。在1173K退火3.6ks时，这些细小的α晶粒长大到直径3mum。在β区轧制的薄板严重剪切区，出现由细小再结晶β晶粒转变而成的极细针状α′-马氏体，退火后不形成等轴组织。在剪切应变小到可以忽略不计的薄片中央层，形成片层结构。在剪切较严重的区域，α相的择优取向随轧制温度的变化而变化。在1323K（β区）轧制的薄板中，只有从(110)<001>取向通过Burgers关系转变的织构，这是bcc金属的剪切织构，称为Goss织构。在α + β区轧制的薄板严重剪切区，织构主要由β相剪切织构和α相剪切织构（<0001>*ND）转变而成。在α + β区轧制的薄板剪切织构强度弱于在β区轧制的薄板。退火后，剪切织构强度增大，出现t织构（<0001>*TD）。在Ti-15V-3Cr-3Sn-3Al板材热轧过程中，表面以下也会出现剪切变形，形成严重的剪切区，并出现一带极细的再结晶晶粒。再结晶晶粒的平均晶粒尺寸随轧制温度的降低和保温时间的延长而减小。热轧后晶粒尺寸为3 μ m，冷轧后退火晶粒尺寸为10 μ m。高速热轧后立即淬火的铜板组织随着轧制温度的升高和压降度的增加，由变形晶粒转变为再结晶晶粒。通过光学和透射电镜观察，得出了热轧后在很短的时间间隔内发生静态再结晶的结论。少

The effects of hot rolling condition on the structure of quenched sheet of Ti-6Al-4V alloy, Ti-15V-3Cr-3Sn-3Al alloy and oxygen free copper are investigated. In high speed hot rolling of Ti6Al-4V sheet, shear deformation produces a severely sheared region beneath the surface. The shear strain increases with increasing rolling temperature and decreases with reducing friction coefficient at the roll surface. Extremely fine recrystallized equiaxed alpha-grains appear in the severely sheared region of the sheet rolled in alpha + beta region. These fine alpha grains grows to diameter of 3mum on annealing at 1173K for 3.6ks. In the severely sheared region of the sheet rolled at beta region, extremely fine acicular alpha'-martensite transformed from fine recrystallized beta grains appears, which does not form equiaxed structure after annealing. In the central layer of the sheet where shear strain is negligibly small, lamellar structure develops. The preferred orientation of alpha phase in the … More severely sheared region changes with rolling temperature. In the sheet rolled at 1323K(beta region), only the transformed texture from (110)<001> orientation through the Burgers' relation, which is the shear texture of bcc metals known as Goss texture. In the severely sheared region of the sheet rolled in alpha + beta region, the texture consists of main components of transformed texture from shear texture of beta-phase and shear texture of alpha-phase (<0001>*ND). The intensity of the shear texture of the sheet rolled in alpha + beta region is weaker than that of the sheet rolled in beta region. After annealing, intensity of shear texture increases and T-texture(<0001>*TD) develops. In hot rolling of Ti-15V-3Cr-3Sn-3Al sheet, shear deformation also accumulates beneath the surface to form severely sheared region and a band of extremely fine recrystallized grains appears. The average grain size of recrystallized grains decreases with decreasing rolling temperature and with decreasing holding time af ter rolling. Grain size is 3mum after hot rolling and grows to 10mum on anneal ing af ter cold rolling. The microstructure of the copper sheet quenched immediately after high speed hot rolling changes from wrought grains to recrystallized grains with increasing rolling temperature and reduction. From the optical and TEM micrographs, it is concluded that static recrystallization occurs within very short interval after hot rolling. Less