Supplementary information

Fig. 18 shows a Young’s modulus–density chart. An important use of this chart is in material selection for

applications in which mass must be minimized. Guidelines corresponding to three common geometries of

loading are shown on the chart. They are used to select materials for elastic design at minimum weight.

As expected, Cr-CrS cermets extend along the overlap area between metals and ceramics and have a

combination of properties of both groups. This chart gives an indication of the possible applications of

this new cermet through a comparison with existing materials. For example, Cr-CrS cermets exhibit a

total overlap with Ti alloys. They also provide the same Young’s modulus as Cu alloys with a much

lower density. The Young’s modulus of Cr-CrS cermet is close to that of steel while its density is about a

half of steel. Moreover, they have a higher Young’s modulus and lower density than Zinc alloys.

Therefore, they can be considered to replace these materials in specific applications because of their low-

cost and relatively convenient manufacturing process, which leads to a lower final price for the

production of these cermets.

Fig. 18 Young’s modulus E plotted against density ρ [31]

A chart showing material strength versus density is shown in Fig. 19. In this chart, the word “strength”

refers to yield strength for metals and polymers, tear strength for elastomers, tensile strength for

composites and woods, and flexural strength (modulus of rupture) for ceramics. For all of them, the

symbol σf is used. This charts helps in materials selection in lightweight plastic design. Guidelines are

drawn on the chart for materials selection for the minimum weight design of ties, beams and plates,

columns, and for yield-limited design of moving components in which inertial forces are important.

According to this chart, Cr-CrS cermets have the same range of strength with Al2O3, SiC, and Si3N4. Its

strength is higher than GFRP, Al, Mg, zinc and lead alloys. It also has overlap with Ti alloys and steels.

These cermets are much lighter than tungsten carbide, although they have a similar strength.

Fig. 19 Strength σf plotted against density ρ (yield strength for metals and polymers, compressive strength for ceramics, tear strength for elastomers, and tensile strength for composites) [31]

One of the most useful of all the charts is shown in Fig. 20, which plots Young’s modulus against

strength. In this chart, the qualifications for “strength” are the same as before. The design guidelines help

with the selection of materials for springs, knife-edges, pivots, diaphragms, and hinges. Contours of

fracture strain or yield strain (σf/E) - the strain at which the material ceases to be linearly elastic- appear

as a series of parallel lines. Cr-CrS cermets lie on the 0.01 contour, as good as composites, woods, and the

best metals.

Fig. 20 Young’s modulus, E, plotted against strength, σf [31]