摘要
采用DSC测试、热镦粗实验、半固态等温处理实验、金相显微镜观察以及Image Pro Plus图像处理软件,研究了等温压缩温度、压缩量和半固态等温处理的温度、保温时间对再结晶重熔(RAP)法制备AlSi7Mg铝合金半固态坯料微观组织的影响。结果表明:等温压缩过程中温度对半固态坯料微观组织的影响不明显,而等温压缩变形量的增大有利于细化半固态坯料微观组织,最优热镦粗参数为温度240℃,变形量40%;半固态等温处理过程中,随保温温度升高,微观组织固相晶粒的尺寸逐渐增大,而随着保温时间延长,半固态组织中固相颗粒的尺寸先缓慢长大再迅速长大然后趋于不变,固相颗粒的圆整度变化较为复杂。通过RAP法制备的AlSi7Mg铝合金半固态坯料平均晶粒尺寸为64~117μm,形状因子为0.76~0.89。低于599℃时,半固态的平均晶粒尺寸的立方粗化线性关系不明显,影响晶粒粗化的机制主要有Ostwald熟化、合并长大、再结晶和熔化;在599℃时,晶粒尺寸的立方粗化线性关系较为明显,此时Ostwald熟化为晶粒粗化的主导机制。
Semi-solid metal processing is a metal-forming technology that combines the advantages of casting and forging, realizing near-net forming high-performance parts with complex structures. Research on semi-solid processing of AlSi7 Mg alloys mainly focuses on rheology, and the preparation of high solid fraction AlSi7 Mg semi-solid billets by the solid phase method has been largely neglected. In fact, semi-solid technology is more significant than casting at higher solid fractions. The present study investigates semi-solid billets of AlSi7 Mg aluminum alloy with a high solid fraction, prepared by the recrystallization and partial re-melting(RAP) method. The effects of upsetting temperature, compression ratio,semi-solid isothermal treatment temperature, and holding time on the billet microstructure were investigated by DSC test, upsetting experiment, semi-solid isothermal treatment experiment, OM observations, and Image Pro Plus image processing software. The microstructure of the semi-solid billet during isothermal compression was slightly affected by temperature but was beneficially refined by increasing the compression ratio. The optimal hot upsetting parameters were 240 ℃ and 40% deformation. During the semi-solid isothermal treatment, increasing the holding temperature gradually increased the size of the solid phase grains in the microstructure. As the holding time increased, the solid phase particles in the semi-solid structure initially grew slowly, and thereafter rapidly grew to a stable size. The changes in roundness of the solid particles were more complicated. The average grain size of the billet prepared by the RAP method was 64~117 μm, and the shape factor was 0.76~0.89. The linear relationship between cubic coarsening of the average semi-solid grain size and isothermal time was nonobvious at isothermal temperatures below 599 ℃ but was evident at temperatures of 599 ℃. Below 599 ℃, the grain coarsening is affected by Ostwald ripening, coalescence, recrystallization, and melting;while at 599 ℃, the grain coarsening was dominated by Ostwald ripening.
作者
姜巨福
张逸浩
刘英泽
王迎
肖冠菲
张颖
JIANG Jufu;ZHANG Yihao;LIU Yingze;WANG Ying;XIAO Guanfei;ZHANG Ying(School of Materials Science and Engineering,Harbin Institute of Technology,Harbin 150001,China;School of Mechatronics Engineering,Harbin Institute of Technology,Harbin 150001,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第6期703-716,共14页
Acta Metallurgica Sinica
基金
国家重点研发计划项目No.2019YFB2006500
国家自然科学基金项目No.51875124。
关键词
材料合成与加工工艺
半固态坯料
再结晶重熔
微观组织
ALSI7MG
synthesizing and processing technics for material
semi-solid billet
recrystallization and remelting
microstructure
AlSi7Mg
