问题： Mtalab中什么函数可以合并函数图像的重叠部分（图 1），一同附上希望得到的效果图（图 2）以及程序代码。烦请大神指点迷津。
受Matlab功力所限，程序颇有繁琐，在R2017b版本上可以运行，还望大神不喜勿喷。
以下 图 1
以下 图2
Matlab程序代码：

%以下 x;[%Al],y:[%Mg]，MgO-二阶+[%O]=[0.0003 0.0005 0.001 0.0015]
z=0.001
f = @(x,y) -280.3.*y-1.29.*x-426.05.*z+log10(y)+log10(z)+350137.*z.^2-20050.*y.^2-0.01.*x.^2-150.*x.*y+401462.*y.*z+72.05.*x.*z++6.79
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'r'; 
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on
z=0.0005
f = @(x,y) -280.3.*y-1.29.*x-426.05.*z+log10(y)+log10(z)+350137.*z.^2-20050.*y.^2-0.01.*x.^2-150.*x.*y+401462.*y.*z+72.05.*x.*z++6.79
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'g';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on
z=0.0015
f = @(x,y) -280.3.*y-1.29.*x-426.05.*z+log10(y)+log10(z)+350137.*z.^2-20050.*y.^2-0.01.*x.^2-150.*x.*y+401462.*y.*z+72.05.*x.*z++6.79
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'black';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on
z=0.0003
f = @(x,y) -280.3.*y-1.29.*x-426.05.*z+log10(y)+log10(z)+350137.*z.^2-20050.*y.^2-0.01.*x.^2-150.*x.*y+401462.*y.*z+72.05.*x.*z++6.79
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'blue';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on

%以下 x;[%Al],y:[%Mg]，MgAl2O4-二阶+[%O]=[0.0003 0.0005 0.001 0.0015]
z=0.001
f = @(x,y) -1124.46.*y-4.72.*x-430.52.*z-80200.*y.^2-0.04.*x.^2+350216.64.*z.^2+178826.*y.*z+978.14.*x.*z-600.*x.*y+log10(y)+2.*log10(x)+4.*log10(z)+20.54
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'r';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on
z=0.0005
f = @(x,y) -1124.46.*y-4.72.*x-430.52.*z-80200.*y.^2-0.04.*x.^2+350216.64.*z.^2+178826.*y.*z+978.14.*x.*z-600.*x.*y+log10(y)+2.*log10(x)+4.*log10(z)+20.54
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'g';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on
z=0.0015
f = @(x,y) -1124.46.*y-4.72.*x-430.52.*z-80200.*y.^2-0.04.*x.^2+350216.64.*z.^2+178826.*y.*z+978.14.*x.*z-600.*x.*y+log10(y)+2.*log10(x)+4.*log10(z)+20.54
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'black';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on
z=0.0003
f = @(x,y) -1124.46.*y-4.72.*x-430.52.*z-80200.*y.^2-0.04.*x.^2+350216.64.*z.^2+178826.*y.*z+978.14.*x.*z-600.*x.*y+log10(y)+2.*log10(x)+4.*log10(z)+20.54
fp=fimplicit(f,[0 2 0 0.02])
fp.Color = 'blue';
fp.LineStyle = '-';
fp.LineWidth = 2;
hold on