The solubility of Cu in Ag is zero at room temperature and it is same for Ag in Cu. solubility starts from 400deg C and reaches to max . Solubility of Of 8.8 wt% at 800degC.
However u can attain a solubility limit at RT, by solutionizing at 800C and water quench it which is called the supersaturated solid solubility of Cu in Ag at RT .