Instead of saving it to a file, save it to php://outputDocs:
$objWriter->save('php://output');
This will send it AS-IS to the browser.
You want to add some headersDocs first, like it's common with file downloads, so the browser knows which type that file is and how it should be named (the filename):
// We'll be outputting an excel file
header('Content-type: application/vnd.ms-excel');
// It will be called file.xls
header('Content-Disposition: attachment; filename="file.xls"');
// Write file to the browser
$objWriter->save('php://output');
First do the headers, then the save. For the excel headers see as well the following question: Setting mime type for excel document.