外熔体温度对7075/6061复合铸锭组织与性能的影响

Effects of Outside Melt Temperature on Microstructure and Properties of 7075/6061 Bimetallic Composite Material

摘要:

具有多性能多功能的双金属复合材料是目前材料研究的热点之一。通过固/液复合铸造技术制备了具有“半固态显微组织/枝晶组织”分布特征的包覆型7075/6061复合铸锭,研究了外熔体温度对该复合铸锭界面组织形态与力学性能的影响规律,探讨了该复合铸锭的界面结合机制。结果表明：外熔体温度760 ℃、半固态坯料预热温度300 ℃、保温40 min、空冷条件时,制备的7075/6061双金属复合铸锭的显微组织分布与形态特征较好、抗压强度较高；随着外熔体温度的升高,内层7075合金半固态坯料的近球状α-Al固相颗粒逐渐粗大、球形化逐渐减弱；复合界面处内层半固态坯料局部重熔的现象逐渐增加,界面附近的半固态显微组织形态呈：球状固相颗粒合并长大、非球状化、枝晶化的演变规律；室温压缩时,复合铸锭以圆柱体轴线呈45°角方向裂开,而非复合界面方向。

关键词:双金属复合材料;固/液复合铸造;铝合金;外熔体温度;半固态组织

Abstract:

Bimetal composite materials having multifunction and more performance are one of the research focuses, at present. And then, the 7075/6061 cladding bimetal composite ingots with “semi-solid microstructure / dendrite microstructure” distribution characteristic were prepared by the solid / liquid metals compound casting. Interfacial morphology and mechanical properties of the ingots with different melt temperatures were analyzed and tested. At last, the interface bonding mechanism of the ingot was discussed. The results show that the 7075/6061 cladding bimetal composite ingot has a advantageous microstructure distribution and morphology, and has the best compressive strength, while the parameters are the outside melt temperature 760 ℃, the billet pre-temperature 300 ℃, holding time 40 min and air cooling. With the increasing of the outside melt temperature, the near-spheroidal α-Al solid particles of the semi-solid billets of the inner layer 7075 alloy are more coarsening and more non-spherical, the remelted area of the semi-solid billet at the bonding interface also increase. Otherwise, as the outside melt temperature increasing, an evolution rule of the semi-solid microstructures nearby the bonding interface is occurred following: near-spheroidal solid particles merging and growing, non-spherical crystal, dendritic crystal. During the compression mechanical property test at ambient temperature, the samples fracture along 45° angle direction to axis, and not along the bonding interface.

Key words:bimetal composite material; solid/liquid metal compound cast; aluminum alloy; outside melt temperature; semi-solid microstructure