通过合理的成分设计制备了一种大热输入药芯焊丝,在实验室进行了大热输入焊接试验,研究在大热输入焊接条件下焊缝金属的组织与韧性。结果表明:在热输入量为360 k J/cm大热输入焊接条件下,焊缝金属中形成了大量的细小弥散分布的夹杂物,并以夹杂物为核心诱导生成了相互交叉互锁的针状铁素体(AF)组织,AF晶粒间形成了大量的大角度晶界结构,是焊缝金属具有较高的冲击韧性的原因;通过进一步对夹杂物组成进行分析,发现在夹杂物周围形成了贫锰区,确定了贫锰区机制为夹杂物形成AF相变机理。
Hardness and microstructure evolutions in 1050 aluminum alloy prepared by equal-channel angular pressing(ECAP) were investigated by hardness testing, optical microscopy, and transmission electron microscopy after samples were annealed at different temperatures for 1 h both in the absence and presence of a 12-T magnetic field. The results showed that the hardness of samples after magnetic annealing were lower than that of samples after normal annealing at 150–250°C, but it was higher than that of samples after normal annealing at >250°C. During annealing, the rate of softening was faster, and the grains were more homogeneous in 8-ECAPed samples than in 2-ECAPed samples. A rapid grain growth occurred when 2-ECAPed samples were annealed at high temperature(≥300°C). The magnetic field enhanced the mobility of dislocations and grain boundaries. A more homogeneous grain size was observed in samples prepared under an applied magnetic field.
Yi-heng CaoPin-feng JiaKang WangLi-zi HePing WangJian-zhong Cui
This work was aimed to study the interfacial microstructures and three-point bending properties of Al/Cu/Al bimetallic laminates produced by the asymmetrical roll bonding and annealing. It is found that the microstructure and bonding strength of the Al/Cu interface are different with those of the Cu/Al interface. The interfacial microstructure of Cu/Al interface is improved due to the large interfacial plastic deformation caused by the different rotation speeds of roll in the asymmetrical roll bonding process. The bonding strength between Al and Cu layer can be enhanced by the moderate atomic diffusion, but is dramatically depressed by the formation of intermetallic compounds in the interface.The bending strength of bimetallic laminates is enhanced when the Cu/Al interface is loaded in tension because of the improvement of stress transition and damping by the Cu/Al interface during the three-point bending deformation. The bending fracture reveals that the interfacial cracks can be inhibited from the restricted stress concentration in the improved Cu/Al interface.
The semi-solid 6061 aluminum alloy castings with t'me equiaxed nondendritic grains are obtained by means of electromagnetic casting method.Appropriate casting technical parameters are casting temperature---720℃,casting speed---100 mm/min,cooling water amount---0.09 m^3/min.The temperature field in the electric stove reheated to the liquid-solid zone is homogeneus and the prope reheating temperature is 630℃.When the mould temperature is 300-500℃,the parts used in automobiles can be thixoformed successfully,itsσ_b is 392 MPa,vigid 142.3 HV andδ_5 11.5%after T6 heat treatment.
