At the last Ally Pally Model Engineering Exhibition I bought a small pack of a 'Techno-Weld' product for welding aluminium.
I have been restoring an old Villiers engine and discovered a previous 'engineer' had cracked the crankcase end casting and with very little effort the cracked part just came away!
Never used Techno Weld before but decided to give it a go on this casting so prepared both parts as suggested incorporating an area both sides to hold a fillet. Jigged it all up and using a large soft flame heated the parts. Didn't measure the temperature but 380c is recommended, must have been about right as the welding stick just flowed in, couldn't believe it!
Really impressed with the repair which has now been turned to finished size.
No connection with the company but very impressed with the product, so much so I emailed them to let them know – but the company was dissolved in October!
Such a shame.
Alan