Not in SLI, no.
SLI requires 2 GPUs with the same chips (brand/model doesn't matter)...... the 750TI doesn;t support SLI anyway.
You *could* use the cards outside of SLI..... for example:
1. with the 750TI as a dedicated PhysX card.
2. With EMA "Explicit Multi Adapter" inside DX12.
Even though you *could*, it's not recommended.
1. PhysX support is limited, and with the wide performance disparity between the two, the 750TI would likely hinder the 1070 rather than benefit it.
2. EMA support is limited to Ashes of the Singularity currently, and isn't seeing the widespread adoption that was hoped for (and I don't know how much benefit a 750TI would bring to a 1070 if any)