2*p1*p2/(p1+p2)
假设两种金属的质量为m,体积分别为v1和v2
v1=m/p1 v2=m/p2
合金的密度p=2m/(v1+v2)=2m/(m/p1+m/p2)=2*p1*p2/(p1+p2)