连续柱状晶CuAlNi合金无模拉拔过程中的组织性能演变

在进料速率0.5 mm/s,冷热源距离15 mn保持不变,拉拔速率0.8—1.1 mm/s,变形温度650—900℃的条件下,对连续柱状晶组织Cu-14.0%Al-3.8%Ni(质量分数)合金线材进行了无模拉拔实验,研究了无模拉拔工艺与合金显微组织和力学性能的关系,并对变形后合金组织性能演变的机理进行了探讨.结果表明:平直晶界连续柱状晶合金线材经无模拉拔变形后,可形成平直晶界和锯齿状晶界连续柱状晶、不完全动态再结晶和完全动态再结晶4种微观组织.在变形温度650℃,拉拔速率0.80.9 mm/s的范围内,变形后合金仍然保持平直晶界连续柱状晶组织;随着变形温度和拉拔速率的提高,连续柱状晶的平直晶界向锯齿状晶界转变.当拉拔速率为0.9 mm/s,变形温度上升至850℃时,合金呈现出明显的不完全动态再结晶的组织特征,即原始柱状晶粒沿变形方向拉长变细,在部分锯齿状晶界处有细小的动态再结晶晶粒产生;继续升高温度至900℃,合金发生完全动态再结晶,大量等轴、尺寸较大的动态再结晶晶粒完全取代了变形的柱状晶粒.拉拔变形后合金线材的抗拉强度随着变形温度的升高先小幅度增加然后显著降低,而伸长率则单调降低.

MICROSTRUCTURE AND MECHANICAL PROPERTIES EVOLUTIONS OF CONTINUOUS COLUMNARGRAINED CuA1Ni ALLOY WIRES DURING DIELESS DRAWING PROCESS

Dieless drawing experiments of continuous columnar-grained Cu-14.0%Al-3.8%Ni (mass fraction) alloy wires were carried out at drawing speeds of 0.8—1.1 mm/s and deformation temperatures of 650—900℃,when the feeding speed and distance between the heating and the cooling sources kept invariant at 0.50 mm/s and 15 mm,respectively.Effects of dieless drawing parameters on the microstructure and mechanical properties of the alloy were investigated,and the mechanism of microstructure and mechanical properties evolutions of the deformed alloy was discussed.It was found that the straight continuous columnar-grained boundaries of the alloy wires evolved into regular small zigzag,disordered large zigzag and recrystallized boundaries.When the deformation temperature was 650℃and the drawing speed was 0.8 and 0.9 mm/s,the alloy remained continuous columnar grains with straight boundaries after dieless drawing,while the straight columnar-grained boundaries gradually transformed into zigzag boundaries with the deformation temperature and drawing speed increasing.When the drawing speed was 0.9 mm/s and the deformation temperature up to 850℃,the alloy exhibited obviously incomplete dynamic recrystallized microstructure characteristic,i.e.the original columnar grains were elongated along the deformation direction, and small dynamic recrystallized grains generated at parts of zigzag grain boundaries.The alloy occurred complete dynamic recrystallization at the deformation temperature of 900℃,and the deformed columnar grains were completely replaced by numerous equiaxed dynamic recrystallized grains with larger size.The tensile strengths of the alloy after dieless drawing first showed a very modest increase trend and then decreased greatly,while the elongations kept decrease.