SEATTLE — Around the time the iPad came out more than two years ago, Microsoft executives got an eye-opening jolt about how far Apple would go to gain an edge for its products.

Microsoft learned through industry sources that Apple had bought large quantities of high-quality aluminum from a mine in Australia to create the distinctive cases for the iPad, according to a former Microsoft employee involved in the discussions, who did not wish to be named talking about internal matters.

The executives were stunned by how deeply Apple was willing to reach into the global supply chain to secure innovative materials for the iPad and, once it did, to corner the market on those supplies. Microsoft’s executives worried that Windows PC makers were not making the same kinds of bets, the former employee said.

The incident was one of many over the last several years that gradually pushed Microsoft to create its own tablet computer, unveiled last week. The move was the most striking evidence yet of the friction between Microsoft and its partners on the hardware side of the PC business. It is the first time in Microsoft’s almost four-decade history that the company will sell its own computer hardware, competing directly with the PC makers that are the biggest customers for the Windows operating system.