Nanoparticles Enabled Mechanism for Hot Cracking Elimination in Aluminum Alloys
Nanoparticles Enabled Mechanism for Hot Cracking Elimination in Aluminum Alloys
复制标题
纳米粒子消除铝合金热裂纹的机理
DOI：
10.1007/s11661-021-06302-9
复制
发表时间：
2021-05-13
影响因子：
2.8
通讯作者：
Li, Xiaochun
中科院分区：
文献类型：
--
作者：
Sokoluk, Maximilian;Yuan, Jie;Li, Xiaochun
热裂纹一直是许多高性能铝合金（如7075、6061和2024合金）凝固加工的长期挑战。纳米处理通过在金属基体中添加低含量的陶瓷纳米颗粒，可以有效降低铝合金在铸造、焊接和增材制造等凝固过程中的热裂敏感性。虽然以前的研究表明，陶瓷纳米颗粒增强异质形核，抑制晶粒生长，并修改各种合金的凝固过程中的第二相，没有系统的研究已经进行了调查的热裂纹消除不同的纳米颗粒在不同的合金系统的潜在机制。在这项工作中，TiC和TiB 2纳米粒子已被纳入到热裂纹敏感铝合金7075，6061，和2024，并进行了详细的热分析和微观结构的研究，以调查纳米粒子启用消除热裂纹的主要机制。结果发现，潜在的机制是由于不寻常的修改的晶粒和金属间化合物相，以及更高的液体分数在凝固的最后阶段。更具体地，纳米颗粒能够实现更快的成核，具有逐渐的潜热释放、球形铝α-晶粒的有效生长限制（特别是通过TiC纳米颗粒）、金属间相的显著改性、以及由于在固化的终端阶段纳米颗粒诱导的扩散阻塞而导致的非平衡共晶的更高的液体分数。
Hot cracking has been a long-term challenge for the solidification processing of many high-performance aluminum alloys, such as 7075, 6061, and 2024 alloys. Nano-treating, by adding a low loading of ceramic nanoparticles into a metal matrix, can effectively reduce the hot cracking susceptibility of aluminum alloys during solidification processes such as casting, welding, and additive manufacturing. While previous studies have shown that ceramic nanoparticles enhance heterogeneous nucleation, inhibit grain growth, and modify secondary phases during solidification of various alloys, no systematic study has been conducted to investigate the underlying mechanisms of hot cracking elimination by different nanoparticles on different alloy systems. In this work, TiC and TiB2 nanoparticles have been incorporated into hot crack susceptible aluminum alloys 7075, 6061, and 2024, and a detailed thermal analysis and microstructure study were carried out to investigate the nanoparticle-enabled principal mechanisms of hot cracking elimination. It is discovered that the underlying mechanism is attributed to the unusual modification of both grains and intermetallic phases as well as a much higher liquid fraction at the final stage of solidification. More specifically, nanoparticles enable faster nucleation with a gradual latent heat release, an effective growth restriction of spherical aluminum alpha-grains (especially by TiC nanoparticles), a significant modification of the intermetallic phases, and a higher liquid fraction of non-equilibrium eutectic due to nanoparticle-induced diffusion blockage at the terminal stages of solidification.