不同热变形工艺大塑性变形加工超细晶1570C铝合金的组织、强度和超塑性

将Al-5Mg-0.18Mn-0.2Sc-0.08Zr-0.01Fe-0.01Si(质量分数,%)合金铸锭进行多向等温锻造(应变12)或等径角挤压(应变10,325℃),再进行热轧(325℃)和冷轧(20℃),对比研究合金变形后的组织和力学行为。结果表明,对(亚)晶粒尺寸dUFG=2μm的超细晶组织合金进行多向等温锻造后,其室温延展性提高,超塑性伸长率可达2800%。通过热轧进一步细化晶粒,后续再通过冷轧形成高位错密度的严重变形组织,合金的屈服/极限抗拉强度从多向等温锻造后的235/360 MPa分别提高到热轧和冷轧后的315/460 MPa和400/515 MPa。同时,热轧使超塑性伸长率提高到4000%,而冷轧后的伸长率仍然足够高(高达1500%)。与多向等温锻造相比,经等径角挤压后合金的晶粒细化程度更高(dUFG=1μm),强度和超塑性性能均得到提高。然而,热轧后此效果有所减弱,加工后的板材具有同等的性能。与多向等温锻造后再冷轧的合金相比,经等径角挤压后再冷轧的合金强度更高,超塑性性能略好。

Structure,strength and superplasticity of ultrafine-grained 1570C aluminum alloy subjected to different thermomechanical processing routes based on severe plastic deformation

A comparative study of the structure and mechanical behavior of an Al-5 Mg-0.18 Mn-0.2 Sc-0.08 Zr-0.01 Fe-0.01 Si(wt.%)alloy ingot subjected to multidirectional isothermal forging(MIF)to a strain of 12 or equal-channel angular pressing(ECAP)to a strain of 10 at 325℃,and subsequent warm and cold rolling(WR and CR)at 325 and 20℃,was performed.The results showed that the MIF process of ultrafine-grained structure with a(sub)grain size dUFG=2μm resulted in enhanced room-temperature ductility and superplastic elongation up to 2800%.Further grain refinement under WR as well as development of a heavily-deformed microstructure with high dislocation density by subsequent CR resulted in a yield/ultimate tensile strength increase from 235/360 MPa after MIF to 315/460 and 400/515 MPa after WR and CR,respectively.Simultaneously,WR led to improved superplastic elongation up to 4000%,while after CR the elongation remained sufficiently high(up to 1500%).Compared with MIF,ECAP resulted in more profound grain refinement(dUFG=1μm),which promoted higher strength and superplastic properties.However,this effect smoothed down upon WR,ensuring equal properties of the processed sheets.CR of the ECAPed alloy,in contrast,led to higher strengthening and slightly better superplastic behavior than those after CR following MIF.