His smile died and the look in his face hardened.

他的微笑消失了，脸上的表情突然显得严峻。

《柯林斯英汉双解大词典》

His face hardened when talked about the battle.

在谈到那次战斗时，他的表情严峻起来。

youdao

It is an oft-repeated story among coastal families that survived and are now returning to their neighborhoods, the mud hardened, to search through the wreckage and face their demons.

在附近的家庭中都有这样的故事，幸存的现在返回到他们居住的地方，在残骸中寻找，直面他们的不幸。

youdao

The indignant man loomed over Hadley, his angular face hardened with strain.

NEWYORKER: Pumpkin Head

Kentucker and Rose face their evanescent intimacy with sharp, anti-romantic wisdom, while the more practical, less hardened Jake and Lucy suffer for their heightened ideals and expectations.

NEWYORKER: Open Five