Thus arsenic, antimony, bismuth, tin or zinc render the metal brittle, so that it fractures under a die or rolling mill; copper, on the other hand, increases its hardness, makes it tougher and more readily fusible.
He couldn't help thinking his mama had been a little tougher when she found out about the Immortals.
In metal bridges wrought iron has been replaced by mild steel - a stronger, tougher and better material.
They are of a tougher fibre than the Aroras; sturdy and self-reliant, slow to speak but quick to strike.
The best poles are obtained in Norway from small, slender, drawn-up trees, growing under the shade of the larger ones in the thick woods, these being freer from knots, and tougher from their slower growth.
She's tougher than Cynthia Byrne used to be.
Lignite and cannel are usually dull and earthy, and of an irregular fracture, the latter being much tougher than the black coal.