Update User Display Name in SharePoint
  Update User Display Name in SharePoint:      To force a manual sync for the user properties from the Active Directory   Set-SPUser -Identity 'domain\userid' –Web http://WebApp:Port –SyncFromAD   However to apply a global refresh for all users from the Active Directory we can use this:     Get-SPUser –Web http://WebApp:Port | Set-SPUser –SyncFromAD