You can't produce good AZ31 material using powder metallurgy. No matter how good your shielding gas or vacuum, this material will contain a lot of magnesium oxide.

You can try sintering at 300 degree, as best formability temerature for AZ31 samples are between 250-325 degree.

Dear P. Bharathi

As Vadim Verlotski sir said, it's very difficult to produce magnesium-based materials by powder metallurgy. Magnesium is highly reactive. You need vacuum conditions for mixing, compaction and sintering. If you can do that, sintering temperature is around 0.8 times of melting (750 K). Sintering temperature will be around 2hrs. But, it highly depends on sintering conditions.