For $\mathrm{Al}-4.5 \mathrm{wt} \% \mathrm{Cu}$ alloy, the correct sequence of precipitation during age hardening at room temperature is
- GP zone $\rightarrow \theta^{\prime \prime} \rightarrow \theta^{\prime} \rightarrow \theta$
- GP zone $\rightarrow \theta^{\prime} \rightarrow \theta^{\prime \prime} \rightarrow \theta$
- GP zone $\rightarrow \theta^{\prime \prime} \rightarrow \theta \rightarrow \theta^{\prime}$
- GP zone $\rightarrow \theta \rightarrow \theta^{\prime} \rightarrow \theta^{\prime \prime}$
