In this study, the heat treatment process of a high-chromium cast iron (HCCI) alloy prepared via 128 MPa squeeze casting at different subcritical quenching temperatures was investigated. The results showed that subcritical heat treatment can change the martensite content, the carbide type and size of the squeeze casting HCCI microstructure. Furthermore, it was revealed that the subcritical quenching heat treatment can improve the hardness of the liquid-forged HCCIs. When the quenching temperature increased from 500 °C to 530 °C, the hardness of the alloy increased significantly, reaching a maximum value of 57 HRC. Thereafter, if the temperature continued to rise to 630 °C, the hardness decreased rapidly. For impact toughness, when the quenching temperature was 500 °C, the toughness of alloy increased by 0.9 J/cm2 than that of the no heat treatment group. If the quenching temperature continued to increase, the toughness was reduced. Taking hardness and toughness into account, the microstructure evolution diagram of the optimal process-500 °C subcritical quenching process was established, various characterisation techniques were used to gain insights into the optimal heat treatment process. Compared with high temperature heat treatment, subcritical heat treatment can improve the performance of the HCCI alloy and reduce costs.

It is still highly desired to develop efficient, resource-abundant and inexpensive electrocatalysts to improve the sluggish kinetics of oxygen evolution reaction (OER) in electrochemical water splitting systems. In this work, the large-area ultrathin (2.52 nm thick) Ce-doped La2O3 nanofilms were developed via a facile and reliable ionic layer epitaxy (ILE) method with different Ce content. The ultrathin Ce-doped La2O3 nanofilm with optimum composition of La1.22Ce0.78O3 exhibited an excellent OER performance with a very low overpotential of 221 mV at 10 mA cm-2 and a small Tafel slope of 33.7 mV dec-1. A remarkable high mass activity of 6263.2 A g-1 was also obtained from ultrathin La1.22Ce0.78O3 nanofilm at the overpotential of 221 mV. Such a high mass activity was three orders of magnitude higher than state-of-the-art commercial IrO2 powders (3.8 A g-1) and more than 30 times higher than La2O3 nanofilm (196.7 A g-1) without Ce doping at the same overpotential. This high mass activity was even significantly higher than other recently reported typical OER catalysts. The substantial OER performance gain by the Ce doping was attributed to the improved conductivity and electrochemical active surface areas of nanofilms as a result of favorable tuning on the charge transfer and electronic structures. This work provides a promising approach to develop high-performance two-dimensional (2D) electrocatalysts by effective heteroatom doping strategy.

Al-Cu3-Si-Mg wheel hubs were prepared by molten metals die forging (MMDF). The as-cast microstructure morphology of the alloy formed under pressure was observed by optical microscope and scanning electron microscope. The granular phases θ (Al2Cu) were distributed in the α-Al grains, and the cross phases β (Mg2Si) grew near the grain boundary in the α-Al grains. Polygonal compounds φ (AlxTi9La2Ce6Cu) and irregular eutectic structures mainly formed by (α+Al2Cu) eutectic formed under non-equilibrium solidification were found at the grain boundaries. Q (Al5Cu2Mg8Si6) phases were found at the intersection of grain boundaries. With the increase of pressure, the proportion of irregular eutectic structures (α+Al2Cu) decreased from 7.3% to 5.2%. Combined with microstructure analysis and thermodynamic software analysis, the non-equilibrium solidification path was determined as follows: L→L+φ→├ L+α┤+φ→├ L+(α+e)+α+φ→(α+e)+Q┤+α+φ→(α+e)+Q┤+[α+θ]+φ→(α+e)+Q┤+[α+θ+β]+φ