A.Al B.Fe C.Cu D.Zn
A.Cr12MoV B.Cr12 C.W18Cr4V D.T12
A.應(yīng)盡量大 B.應(yīng)取中間值 C.應(yīng)盡量小 D.應(yīng)隨制件尺寸減小