Microstructure and mechanical properties of strontium-modified ADC12 alloy processed by heat treatment
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The effects of heat treatment and strontium (Sr) addition on the microstructure and mechanical properties of ADC12 alloys were investigated, and two-stage solution treatment was introduced. The results indicated that the addition of Sr obviously refined the microstructure of ADC12 alloys. When 0.05 wt% Sr was added into the alloy, the eutectic Si phase was fully modified into fine fibrous structure; α-Al and β-Al5FeSi phases were best refined; and the eutectic Al2Cu phase was modified into block-like Al2Cu phase that continuously distributed at the grain boundary. The ultimate tensile strength (UTS) (270.63 MPa) and elongation (3.19%) were increased by 51.2% and 73.4% respectively compared with unmodified alloys. After the two-stage solution treatment (500 °C, 6 h+520 °C, 4 h), for 0.05 wt% Sr modified ADC12 alloys, the Si phases transformed into fine particle structure and Al2Cu phases were fully dissolved. The peak hardness value of the alloys processed by the two-stage solution treatment was increased by 8.3% and 6.8% respectively compared to solution treatment at 500 °C and 520 °C. After the aging treatment (175 °C, 7 h), the hardness and UTS were increased by 38.73% and 13.96% respectively when compared with the unmodified alloy.
Key wordsADC12 alloy strontium heat treatment microstructure mechanical properties
本文研究了锶(Sr)变质、单级及二级固溶处理以及时效处理对ADC12 合金显微组织及力学 性能的影响。结果表明,Sr 的添加可以显著改善ADC12 合金的显微组织。当Sr 添加量为0.05 wt%时, 共晶硅相完全转变为细小纤维状,α-Al 相和β-Al5FeSi 相得到了较佳的细化效果,同时Al2Cu 相转变 为块状,并连续分布在晶界处;其极限抗拉强度(270.63 MPa)和伸长率(3.19%)较基体合金分别提高了 51.2%和73.4%。经二级固溶处理(500 °C,6 h+520 °C,4 h)后,共晶硅相转变为细小颗粒状,Al2Cu 相完全溶解;其峰值硬度较500 °C 和520 °C 下单级固溶处理分别提高了8.3%和6.8%。时效处理 (175 °C,7 h)后,其硬度和极限抗拉强度较基体合金分别提高了38.73%和13.96%。
关键词ADC12 合金 锶 热处理 显微组织 力学性能
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